Normalize agent instructions and workplan frontmatter (STATE-WP-0067)

- Align agent files with on-disk workplan prefixes (infer from workplan ids)
- Set workplan domain to registered domain_slug; add topic_slug where applicable
- Repair frontmatter delimiter formatting; migrate legacy task status literals
- Regenerate AGENTS.md, CLAUDE.md, and .claude/rules from State Hub templates

.claude/ralph-loop.local.md

@@ -1,21 +0,0 @@
----
-active: true
-iteration: 1
-session_id: b24b53ca-a25b-4a18-8331-925c4100d39f
-max_iterations: 20
-completion_promise: "HEUREKA"
-workplan_id: SHARD-WP-0004
-workplan_file: workplans/SHARD-WP-0004-computational-knowledge-systems.md
-started_at: "2026-06-14T20:35:07Z"
----
-
-Read the workplan at `workplans/SHARD-WP-0004-computational-knowledge-systems.md`.
-
-If every task has `status: done` AND frontmatter `status: done`:
-run `rm -f .claude/ralph-loop.local.md` first (deactivates the loop so the stop hook exits cleanly),
-then output <promise>HEUREKA</promise>.
-
-Otherwise implement the next `todo` task as described in the workplan.
-Set task `in_progress` when starting, `done` when complete.
-When all tasks are done set frontmatter `status: done`.
-

.claude/rules/agents.md

@@ -0,0 +1,20 @@
+## Kaizen Agents
+
+Specialized agent personas available on demand via the state-hub MCP.
+
+**Discover:** `list_kaizen_agents()` — returns all agents with name, description, category
+**Load:** `get_kaizen_agent("tdd-workflow")` — returns full instructions; read and follow them
+
+Common agents:
+
+| Agent | Category | When to use |
+|-------|----------|-------------|
+| `tdd-workflow` | testing | Step-by-step TDD8 workflow for any feature |
+| `code-refactoring` | quality | Code quality analysis and safe refactoring |
+| `test-maintenance` | testing | Diagnose and fix failing tests |
+| `requirements-engineering` | process | Prevent interface/mock mismatches upfront |
+| `keepaTodofile` | process | Maintain TODO.md during work |
+| `project-management` | process | Track status, determine next steps |
+| `datamodel-optimization` | quality | Optimize dataclasses and data structures |
+
+All 17 agents: call `list_kaizen_agents()` for the full list.

.claude/rules/architecture.md

@@ -0,0 +1,8 @@
+## Architecture
+
+<!-- TODO: Describe the key design decisions and component structure.
+     Key modules, data flows, external integrations, state machines, etc. -->
+
+## Quick Reference
+
+`~/state-hub/mcp_server/TOOLS.md` — MCP tool reference

.claude/rules/credential-routing.md

@@ -0,0 +1,50 @@
+# Credential and access routing
+
+**Audience:** Codex, Claude Code, Grok, and custodian agents that call **llm-connect**
+for inference. Run this check **before** requesting secrets, API keys, SSH access,
+login tokens, or database passwords — in any repo, not only `ops-warden`.
+
+ops-warden **issues SSH certificates only** (`warden sign`, `cert_command`). Every
+other credential need belongs to another subsystem. **Do not** message
+`ops-warden` on State Hub expecting a secret value; the reply is a pointer, not a key.
+
+### Lookup (do this first)
+
+```bash
+warden route find "<describe your need>" --json
+warden route show <catalog-id> --json
+```
+
+Requires the `warden` CLI from `~/ops-warden` (`uv tool install .` or `uv run warden`).
+
+| Agent runtime | How to orient |
+| --- | --- |
+| **Codex / Grok** (shell, HTTP State Hub) | `warden route` commands above; inbox `to_agent=shard-wiki` is for coordination, not secret vending |
+| **Claude Code** (MCP when available) | `get_domain_summary("custodian")` for workstreams; **still** use `warden route` for credential ownership |
+| **llm-connect** (inference service) | Never put secret retrieval in prompts; route custody to OpenBao/operator paths surfaced by `warden route` |
+
+### Quick routing table
+
+| I need… | Owner | ops-warden executes? |
+| --- | --- | --- |
+| SSH cert (`adm`/`agt`/`atm`) | ops-warden | **Yes** — `warden sign` |
+| API key, DB password, provider token | OpenBao (`railiance-platform`) | No — route only |
+| Login / OIDC / MFA | key-cape / Keycloak | No — route only |
+| Authorization decision | flex-auth | No — route only |
+| activity-core → issue-core emission | activity-core + issue-core | No — `warden route show activity-core-issue-sink` |
+| SSH tunnel | ops-bridge (+ `cert_command` from warden) | No — route only |
+
+### Anti-patterns (do not do these)
+
+- `POST /messages/` to `ops-warden` asking for `ISSUE_CORE_API_KEY`, `OPENROUTER_API_KEY`, etc.
+- Inventing `warden secret`, `warden login`, `warden bao`, `warden tunnel` — they do not exist
+- Pasting secrets into Git, State Hub, workplans, logs, or chat
+
+### Other capabilities (reuse-surface)
+
+Non-credential capabilities are usually discovered through **reuse-surface** federation
+(`reuse-surface` registry / `capability.*` indexes). Credential routing is inlined in
+every repo's agent instructions because it is high-frequency, high-risk, and easy to
+get wrong.
+
+**Canon:** `~/ops-warden/wiki/CredentialRouting.md` · catalog `~/ops-warden/registry/routing/catalog.yaml`

.claude/rules/first-session.md

@@ -0,0 +1,38 @@
+## First Session Protocol
+
+Triggered when `get_domain_summary("consumer")` shows **no workstreams**.
+The project is registered but work has not yet been structured.
+
+**Step 1 — Read, don't write**
+- `~/the-custodian/canon/projects/consumer/project_charter_v0.1.md` — purpose, scope
+- `~/the-custodian/canon/projects/consumer/roadmap_v0.1.md` — planned phases
+- Scan repo root: README, directory structure, existing code or docs
+
+**Step 2 — Survey in-progress work**
+Look for TODOs, open branches, half-finished files. Note done vs. started but incomplete.
+
+**Step 3 — Propose workstreams to Bernd**
+Propose 1–3 workstreams — each a coherent strand, weeks to months, anchored to a
+roadmap phase. **Wait for approval before creating.**
+
+**Step 4 — Create workplan file first, then DB record (ADR-001)**
+```
+workplans/SHARD-WP-NNNN-<slug>.md   ← write this first
+```
+Then register in the hub:
+```
+create_workstream(topic_id="4c2e5315-2cb9-447c-9d16-a39bdb0aabd0", title="...", owner="...", description="...")
+create_task(workstream_id="<id>", title="...", priority="high|medium|low")
+```
+
+**Step 5 — Record the setup**
+```
+add_progress_event(
+    summary="First session: structured consumer into N workstreams, M tasks",
+    event_type="milestone",
+    topic_id="4c2e5315-2cb9-447c-9d16-a39bdb0aabd0",
+    detail={"workstreams": [...], "tasks_created": M}
+)
+```
+
+<!-- Delete or archive this file once past first session -->

.claude/rules/repo-boundary.md

@@ -0,0 +1,8 @@
+## Repo boundary
+
+This repo owns **shard-wiki** only. It does not own:
+
+<!-- TODO: List what belongs in adjacent repos, e.g.:
+- SSH key management → railiance-infra/
+- State hub code     → state-hub/
+-->

.claude/rules/repo-identity.md

@@ -0,0 +1,5 @@
+**Purpose:** Git-based Markdown wiki orchestrator and federation layer. Python (src/ layout, hatchling, pytest). Early-stage: scaffold + INTENT.md defined, domain model not yet implemented. See INTENT.md for authoritative scope.
+
+**Domain:** consumer
+**Repo slug:** shard-wiki
+**Topic ID:** 4c2e5315-2cb9-447c-9d16-a39bdb0aabd0

.claude/rules/session-protocol.md

@@ -0,0 +1,85 @@
+## Session Protocol
+
+Dev Hub (State Hub API): http://127.0.0.1:8000
+MCP server name in `~/.claude.json`: `dev-hub`
+
+**Step 1 — Orient**
+
+Read the offline-safe brief first — it works without a live hub connection:
+```bash
+cat .custodian-brief.md
+```
+Then call the MCP tool for richer cross-domain context when MCP tools are exposed:
+```
+get_domain_summary("consumer")
+```
+If MCP tools are unavailable in the current agent session, use the REST API:
+```bash
+curl -s "http://127.0.0.1:8000/state/summary" | python3 -m json.tool
+```
+If the hub is offline: `cd ~/state-hub && make api`
+
+**Step 2 — Check inbox**
+With MCP tools:
+```
+get_messages(to_agent="shard-wiki", unread_only=True)
+```
+Mark read with `mark_message_read(message_id)`. Reply or act on coordination
+requests before proceeding.
+
+Without MCP tools:
+```bash
+curl -s "http://127.0.0.1:8000/messages/?to_agent=shard-wiki&unread_only=true" \
+  | python3 -m json.tool
+curl -s -X PATCH "http://127.0.0.1:8000/messages/<id>/read" \
+  -H "Content-Type: application/json" -d '{}'
+```
+
+**Step 3 — Scan workplans**
+```bash
+ls workplans/
+```
+For each file with `status: ready`, `active`, or `blocked`, note pending
+`wait`/`todo`/`progress` tasks.
+
+**Step 4 — Present brief**
+
+1. **Active workstreams** for `consumer` — title, task counts, blocking decisions
+2. **Pending tasks** from `workplans/` + any `[repo:shard-wiki]` hub tasks
+3. **Goal guidance** — if `goal_guidance` in summary:
+   - `needs_workplan`: surface as top action — *"Repo goal '{title}' has no workplan yet"*
+   - `alignment_warnings`: flag if active work is not aligned with current goal
+4. **Suggested next action** — highest-priority open item
+5. **SBOM status** — flag if `last_sbom_at` is unset for this repo
+
+If no workstreams: follow First Session Protocol (`first-session.md`).
+
+**During work:** `record_decision()` · `add_progress_event()` · `resolve_decision()`
+
+> State Hub is a *read model*. Bootstrap tools (`create_workstream`, `create_task`)
+> are First Session Protocol only. Work structure belongs in repo files (ADR-001).
+
+**Session close:**
+With MCP tools:
+```
+add_progress_event(summary="...", topic_id="4c2e5315-2cb9-447c-9d16-a39bdb0aabd0", workstream_id="<uuid>")
+```
+Without MCP tools:
+```bash
+curl -s -X POST http://127.0.0.1:8000/progress/ \
+  -H "Content-Type: application/json" \
+  -d '{"topic_id":"4c2e5315-2cb9-447c-9d16-a39bdb0aabd0","workstream_id":"<uuid>","event_type":"note","summary":"what changed","author":"codex"}'
+```
+If workplan files were modified, ensure the local copy is up to date first:
+```bash
+git -C <repo_path> pull --ff-only
+cd ~/state-hub && make fix-consistency REPO=shard-wiki
+```
+For repos where implementation runs on a remote machine (e.g. CoulombCore),
+use the combined target which pulls before fixing:
+```bash
+cd ~/state-hub && make fix-consistency-remote REPO=shard-wiki
+```
+**C-15** (DB task ahead of file) is normal in multi-machine workflows — writeback
+will sync the file to match DB.  **C-16** (repo behind remote) blocks all writes
+until you pull — intentional to prevent clobbering remote progress.

.claude/rules/stack-and-commands.md

@@ -0,0 +1,19 @@
+## Stack
+
+<!-- TODO: Fill in language, frameworks, and key dependencies -->
+- **Language:**
+- **Key deps:**
+
+## Dev Commands
+
+```bash
+# TODO: Fill in the standard commands for this repo
+
+# Install dependencies
+
+# Run tests
+
+# Lint / type check
+
+# Build / package (if applicable)
+```

.claude/rules/workplan-convention.md

@@ -0,0 +1,40 @@
+## Workplan Convention (ADR-001)
+
+File location: `workplans/SHARD-WP-NNNN-<slug>.md`
+ID prefix: `SHARD-WP-`
+
+Work items originate as files in this repo **before** being registered in the hub.
+
+Canonical workplan/workstream frontmatter statuses are:
+`proposed`, `ready`, `active`, `blocked`, `backlog`, `finished`, `archived`.
+Use `proposed` for a newly drafted plan, `ready` after review against current
+repo state, and `finished` when implementation is complete. `stalled` and
+`needs_review` are derived health labels, not stored statuses.
+
+Closed workplans may be moved to `workplans/archived/` with a completion-date
+prefix: `YYMMDD-SHARD-WP-NNNN-<slug>.md`. The frontmatter id remains
+unchanged; the prefix is only for quick visual reference.
+
+Small opportunistic tasks discovered during another session use **Ad Hoc Tasks**:
+`workplans/ADHOC-YYYY-MM-DD.md`, workstream slug `adhoc-YYYY-MM-DD`, and task ids
+`ADHOC-YYYY-MM-DD-T01`, `T02`, etc. Use adhocs only for low-risk work completed
+directly. Promote anything requiring analysis, design, approval, dependencies, or
+multiple planned phases into a normal workplan.
+
+Ecosystem todos from other agents arrive as `[repo:shard-wiki]` hub tasks —
+visible at session start. Pick one up by creating the workplan file, then registering
+the workstream.
+
+Task blocks use this shape:
+
+```task
+id: SHARD-WP-NNNN-T01
+status: wait | todo | progress | done | cancel
+priority: high | medium | low
+state_hub_task_id: "<uuid>"         # written by fix-consistency — do not edit
+```
+
+Status progression is `todo` → `progress` → `done`; use `wait` for waiting or
+blocked work and `cancel` for stopped work.
+
+<!-- Ralph Loop rules and HEUREKA sequence: ~/.claude/CLAUDE.md — do not duplicate here -->

.custodian-brief.md

@@ -2,41 +2,46 @@
 # Custodian Brief — shard-wiki
 
 **Domain:** whynot  
-**Last synced:** 2026-06-14 21:55 UTC  
+**Last synced:** 2026-06-15 22:57 UTC  
 **State Hub:** http://127.0.0.1:8000 *(adjust if running on a remote machine)*
 
 ## Active Workstreams
 
-### computational / interactive-knowledge systems research
-Progress: 6/8 done  |  workstream_id: `5fc3911a-1c68-4826-bbd2-b892dec8f981`
+### second adapter — git-IS-store shard (contract validation on a new substrate)
+Progress: 0/3 done  |  workstream_id: `9e24eeb0-c0f0-41e6-a1ca-88d71e4139ea`
 
 **Open tasks:**
-- · Processing.org and Processing.js  `0f54cb0e`
-- · Strudel.cc — live-coding REPL  `2b099639`
+- · GitShardAdapter — read over a git working tree/repo  `8a1c7c80`
+- · Write = commit; current_rev = sha (drift)  `b47dfb86`
+- · History adopt + integration with union/overlay  `4c895f42`
 
-### federation architecture design
-Progress: 0/16 done  |  workstream_id: `2af4c46d-cbfd-40ea-a94b-d9e60b0f9945`
+### incremental union maintenance + equivalence index + I-2 verification
+Progress: 0/4 done  |  workstream_id: `78d48bcf-6482-4266-bc81-084b7ec1cd80`
 
 **Open tasks:**
-- · Architecture positioning and boundaries  `ea8fdb22`
-- · Remix primitives: fork, overlay, import, reference  `fb7d4bce`
-- · Equivalent page identity and multi-version presentation  `8f2a333d`
-- · History, attribution, and coordination journal  `5f39f48d`
-- · Union composition layer  `3ff71e11`
-- · Change notification and subscription transports  `9596e5e8`
-- · Information space lifecycle  `38134064`
-- … and 9 more open tasks
+- · Equivalence index: blocking + verify  `842f480b`
+- · Incremental maintenance (delta, not additive)  `2da4e0b8`
+- · I-2 verification: digest + consistency-checker  `b602ce31`
+- · Wire incremental tier behind resolution + views  `2f3d083c`
 
-### shard-wiki requirements from yawex prior art
-Progress: 0/6 done  |  workstream_id: `0ed023a2-760b-4990-b931-8ee1f41ea08f`
+### derived views — wikilinks, BackLinks, RecentChanges, AllPages/SiteMap
+Progress: 0/5 done  |  workstream_id: `2fe15330-ddf6-4b0f-8e55-ada341375d35`
 
 **Open tasks:**
-- · Design federation page-resolution model (yawex state space as inspiration)  `ebc036e4`
-- · Define namespace/path model and page+shard roles  `431b4d28`
-- · Specify union-level derived views (BackLinks, RecentChanges, AllPages, SiteMap, Search)  `564545ec`
-- · Provenance & freshness model for pages/revisions/projections  `738326f5`
-- · Overlay / lightweight-patch model (from yawex append/comment)  `a268de6a`
-- · Markdown link semantics: wikilink + red-link extension  `a7499f3e`
+- · Wikilink + red-link model  `792660c3`
+- · BackLinks (core)  `431a54c3`
+- · RecentChanges (core)  `270c1c31`
+- · AllPages / SiteMap (core)  `898ba43e`
+- · Wiring + integration  `7157544b`
+
+### git-backed DecisionLog + per-space append authority
+Progress: 0/4 done  |  workstream_id: `4fb5b29b-955c-4f37-85cf-58b4643ab1ca`
+
+**Open tasks:**
+- · Git event-store backend (append = commit/object)  `a8fcbb3e`
+- · Per-space append authority (lease)  `62abd162`
+- · Fold over the git log + read-your-writes across processes  `8cc3691e`
+- · Migration + wiring  `281e1db4`
 
 ---
 ## MCP Orientation (when available)

.repo-classification.yaml

@@ -0,0 +1,17 @@
+repo_classification:
+  standard: Repo Classification Standard
+  version: '1.0'
+  classified_at: '2026-06-22'
+  classified_by: agent
+  category: project
+  domain: consumer
+  secondary_domains: []
+  capability_tags:
+  - knowledge
+  - documentation
+  business_stake:
+  - product
+  - experience
+  business_mechanics:
+  - coordination
+  - operation

AGENTS.md

@@ -1,62 +1,219 @@
-# AGENTS.md
+# shard-wiki — Agent Instructions
 
-Guidance for agents working in `shard-wiki`.
+## Repo Identity
 
-## Read First
+**Purpose:** Git-based Markdown wiki orchestrator and federation layer. Python (src/ layout, hatchling, pytest). Early-stage: scaffold + INTENT.md defined, domain model not yet implemented. See INTENT.md for authoritative scope.
 
-1. `INTENT.md` — aspiration and boundaries (stable; architectural changes are rare).
-2. `SCOPE.md` — what we are achieving now and current maturity.
-3. `.custodian-brief.md` — State Hub snapshot (generated; do not edit manually).
+**Domain:** consumer
+**Repo slug:** shard-wiki
+**Topic ID:** `4c2e5315-2cb9-447c-9d16-a39bdb0aabd0`
+**Workplan prefix:** `SHARD-WP-`
 
-## Documentation Layout
+---
 
-This repo follows the CoulombSocial / HelixForge / MarkiTect documentation
-layout (recommendation, not strict law). Efficient retrieval by purpose:
+## State Hub Integration
 
-| Path | Purpose |
-|------|---------|
-| `INTENT.md` | Aspiration and boundaries |
-| `SCOPE.md` | Top-level view of current achievement; closes gap to INTENT |
-| `research/` | Exploration results (`yymmdd-` prefix on files or subdirs) |
-| `demand/` | Inbound requests not yet reviewed into spec or workplans |
-| `spec/` | Implementation guardrails (PRD, TSD, use cases, architecture) |
-| `workplans/` | State Hub–registered implementation tasks |
-| `docs/` | Stakeholder documentation (users, developers, humans, agents) |
-| `wiki/` | Perspective-free interconnected knowledge (wiki UI when connected) |
-| `issues/` | Mirror of relevant open tickets when ticket systems are in use |
-| `history/` | Archived material (`yymmdd-` prefix); out of scope for daily work |
+The Custodian State Hub tracks work across all domains. Interact via HTTP REST —
+there is no MCP server for Codex agents.
 
-**Mode of operation:** close SCOPE → INTENT while learning; refine both as needed.
+| Context | URL |
+|---------|-----|
+| Local workstation | `http://127.0.0.1:8000` |
+| Remote via tunnel | `http://127.0.0.1:18000` |
 
-## Domain Vocabulary
-
-Honor terms from `INTENT.md`: shard, root entity, adapter contract, projection,
-overlay, coordination journal, shard modes. Do not invent parallel vocabulary.
-
-## Build And Test
+### Orient at session start
 
 ```bash
-pip install -e ".[dev]"
-pytest
-ruff check
-ruff format
+# Offline brief — works without hub connection
+cat .custodian-brief.md
+
+# Active workstreams for this domain
+curl -s "http://127.0.0.1:8000/workstreams/?topic_id=4c2e5315-2cb9-447c-9d16-a39bdb0aabd0&status=active" \
+  | python3 -m json.tool
+
+# Check inbox
+curl -s "http://127.0.0.1:8000/messages/?to_agent=shard-wiki&unread_only=true" \
+  | python3 -m json.tool
 ```
 
-## State Hub
+Mark a message read:
+```bash
+curl -s -X PATCH "http://127.0.0.1:8000/messages/<id>/read" \
+  -H "Content-Type: application/json" -d '{}'
+```
 
-Workplans register with State Hub. After workplan changes:
+### Log progress (required at session close)
 
 ```bash
-cd ~/state-hub && make fix-consistency REPO=shard-wiki
+curl -s -X POST http://127.0.0.1:8000/progress/ \
+  -H "Content-Type: application/json" \
+  -d '{
+    "summary": "what was done",
+    "event_type": "note",
+    "author": "codex",
+    "workstream_id": "<uuid>",
+    "task_id": "<uuid>"
+  }'
 ```
 
-Finished or canceled workplans move to `history/` with a `yymmdd-` archive prefix.
+Omit `workstream_id` / `task_id` when not applicable.
 
-## Where To Put New Material
+### Update task status
 
-- Exploratory analysis → `research/yymmdd-<topic>/`
-- Raw feature ask or external requirement → `demand/`
-- Reviewed design ready to guide code → `spec/`
-- Implementation tasks → `workplans/`
-- User/dev/agent how-to → `docs/`
-- Collaborative unstructured notes → `wiki/`
+```bash
+curl -s -X PATCH "http://127.0.0.1:8000/tasks/<task_id>" \
+  -H "Content-Type: application/json" \
+  -d '{"status": "progress"}'
+# values: wait | todo | progress | done | cancel
+```
+
+### Flag a task for human review
+
+```bash
+curl -s -X PATCH "http://127.0.0.1:8000/tasks/<task_id>" \
+  -H "Content-Type: application/json" \
+  -d '{"needs_human": true, "intervention_note": "reason"}'
+```
+
+---
+
+## Session Protocol
+
+**Start:**
+1. `cat .custodian-brief.md` — domain goal and open workstreams (offline-safe)
+2. Check inbox: `GET /messages/?to_agent=shard-wiki&unread_only=true`; mark read
+3. Scan workplans: `ls workplans/` — note `status: ready`, `active`, or `blocked` files and open tasks
+4. Check human-needed tasks: `GET /tasks/?needs_human=true`
+
+**During work:**
+- Update task statuses in workplan files as tasks progress
+- Record significant decisions via `POST /decisions/`
+
+**Close:**
+1. Update workplan file task statuses to reflect progress
+2. Log: `POST /progress/` with a summary of what changed
+3. Note for the custodian operator: after workplan file changes, run from
+   `~/state-hub`:
+   ```bash
+   make fix-consistency REPO=shard-wiki
+   ```
+   This syncs task status from files into the hub DB.
+
+---
+
+## Credential and access routing
+
+**Audience:** Codex, Claude Code, Grok, and custodian agents that call **llm-connect**
+for inference. Run this check **before** requesting secrets, API keys, SSH access,
+login tokens, or database passwords — in any repo, not only `ops-warden`.
+
+ops-warden **issues SSH certificates only** (`warden sign`, `cert_command`). Every
+other credential need belongs to another subsystem. **Do not** message
+`ops-warden` on State Hub expecting a secret value; the reply is a pointer, not a key.
+
+### Lookup (do this first)
+
+```bash
+warden route find "<describe your need>" --json
+warden route show <catalog-id> --json
+```
+
+Requires the `warden` CLI from `~/ops-warden` (`uv tool install .` or `uv run warden`).
+
+| Agent runtime | How to orient |
+| --- | --- |
+| **Codex / Grok** (shell, HTTP State Hub) | `warden route` commands above; inbox `to_agent=shard-wiki` is for coordination, not secret vending |
+| **Claude Code** (MCP when available) | `get_domain_summary("custodian")` for workstreams; **still** use `warden route` for credential ownership |
+| **llm-connect** (inference service) | Never put secret retrieval in prompts; route custody to OpenBao/operator paths surfaced by `warden route` |
+
+### Quick routing table
+
+| I need… | Owner | ops-warden executes? |
+| --- | --- | --- |
+| SSH cert (`adm`/`agt`/`atm`) | ops-warden | **Yes** — `warden sign` |
+| API key, DB password, provider token | OpenBao (`railiance-platform`) | No — route only |
+| Login / OIDC / MFA | key-cape / Keycloak | No — route only |
+| Authorization decision | flex-auth | No — route only |
+| activity-core → issue-core emission | activity-core + issue-core | No — `warden route show activity-core-issue-sink` |
+| SSH tunnel | ops-bridge (+ `cert_command` from warden) | No — route only |
+
+### Anti-patterns (do not do these)
+
+- `POST /messages/` to `ops-warden` asking for `ISSUE_CORE_API_KEY`, `OPENROUTER_API_KEY`, etc.
+- Inventing `warden secret`, `warden login`, `warden bao`, `warden tunnel` — they do not exist
+- Pasting secrets into Git, State Hub, workplans, logs, or chat
+
+### Other capabilities (reuse-surface)
+
+Non-credential capabilities are usually discovered through **reuse-surface** federation
+(`reuse-surface` registry / `capability.*` indexes). Credential routing is inlined in
+every repo's agent instructions because it is high-frequency, high-risk, and easy to
+get wrong.
+
+**Canon:** `~/ops-warden/wiki/CredentialRouting.md` · catalog `~/ops-warden/registry/routing/catalog.yaml`
+
+<!-- REPO-AGENTS-EXTENSIONS -->
+<!-- Append repo-specific agent instructions below this marker.
+     The state-hub template sync preserves content after this line. -->
+
+---
+
+## Workplan Convention (ADR-001)
+
+Work items originate as files in this repo — not in the hub. The hub is a
+read/cache/index layer that rebuilds from files.
+
+**File location:** `workplans/SHARD-WP-NNNN-<slug>.md`
+
+**Archived location:** finished workplans may move to
+`workplans/archived/YYMMDD-SHARD-WP-NNNN-<slug>.md`. The `YYMMDD` prefix is
+the completion/archive date; the frontmatter `id` does not change.
+
+**Ad Hoc Tasks:** small opportunistic fixes discovered during a session use
+`workplans/ADHOC-YYYY-MM-DD.md` with task ids `ADHOC-YYYY-MM-DD-T01`, etc. Use
+this only for low-risk work completed directly; create a normal workplan for
+anything needing analysis, design, approval, dependencies, or multiple phases.
+
+**Frontmatter:**
+
+```yaml
+---
+id: SHARD-WP-NNNN
+type: workplan
+title: "..."
+domain: consumer
+repo: shard-wiki
+status: proposed | ready | active | blocked | backlog | finished | archived
+owner: codex
+topic_slug: ...
+created: "YYYY-MM-DD"
+updated: "YYYY-MM-DD"
+state_hub_workstream_id: "<uuid>"   # written by fix-consistency — do not edit
+---
+```
+
+Use `proposed` for a new draft, `ready` after review against current repo
+state, and `finished` after implementation. `stalled` and `needs_review` are
+derived health labels, not frontmatter statuses.
+
+**Task block format** (one per `##` section):
+
+```
+## Task Title
+
+` ` `task
+id: SHARD-WP-NNNN-T01
+status: wait | todo | progress | done | cancel
+priority: high | medium | low
+state_hub_task_id: "<uuid>"         # written by fix-consistency — do not edit
+` ` `
+
+Task description text.
+```
+
+Status progression: `todo` → `progress` → `done`; use `wait` for waiting/blocked work and `cancel` for stopped work.
+
+To create a new workplan:
+1. Write the file following the format above
+2. Notify the custodian operator to run `make fix-consistency REPO=shard-wiki`
+   (or send a message to the hub agent via `POST /messages/`)

CLAUDE.md

@@ -1,53 +1,12 @@
-# CLAUDE.md
+# shard-wiki — Claude Code Instructions
 
-This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
-
-## Repository status
-
-This is an **early-stage Python repository**. The package scaffold (`src/shard_wiki/`, `tests/`, `pyproject.toml`) exists with only smoke tests — the domain model is not yet implemented. Read `INTENT.md` (aspiration), `SCOPE.md` (current achievement), and `AGENTS.md` (layout and conventions) before designing anything. Close the gap from SCOPE to INTENT via `research/`, `spec/`, and `workplans/`.
-
-## What this project is
-
-`shard-wiki` is a **Git-based Markdown wiki orchestrator and federation layer**, not a wiki engine. It lets multiple heterogeneous wiki-shaped page stores (**shards**) attach to a shared root entity and be presented as a **union of pages**, while preserving each shard's separate storage, provenance, capabilities, and history.
-
-The core job is orchestration across backends — Git repos, repo subdirectories (`wiki/`), Gitea wikis, local folders, Obsidian vaults, WebDAV/Nextcloud directories, Coulomb spaces — never replacing or homogenizing them.
-
-## Core domain model (the concepts code must honor)
-
-These abstractions come from `INTENT.md` and define the architecture. New code should map onto them rather than inventing parallel vocabulary:
-
-- **Shard** — an independently meaningful page store attached to a root entity. Shards have *sovereignty*: their own backend, capabilities, limits, history, and identity model. Not all shards are Git-native.
-- **Root entity / information space** — the joined space that shards attach to. Each information space should have a **Git-addressable coordination layer** (history, patches, review, backup, reconciliation) even when individual shards are not Git-native.
-- **Shard adapter contract** — the versioned interface a backend implements to participate. Adapters are **capability-aware**: the core must model explicitly which operations a shard supports (read, write, diff, merge, lock, version, publish, accept patches) rather than assuming uniformity.
-- **Wiki page model** — a stable, versioned, Markdown-first but backend-neutral representation of pages, paths, links, metadata, revisions.
-- **Projection** — a lazy, cache-like local view of remote/external shard content. Prefer lazy projection over eager copying.
-- **Overlay** — a non-destructive local edit against a remote, read-only, or capability-limited shard, representable as drafts/patches/commits/merge requests *before* destructive application ("overlay before mutation").
-- **Coordination journal** — the Git-backed record of change flows for an information space.
-- **Shard modes** — read-only, write-through, mirrored, projected, cached, canonical.
-
-## Design constraints to enforce in code
-
-These are hard boundaries from `INTENT.md`; treat violations as design bugs:
-
-- **Mechanism over policy.** Provide primitives for federation, sync, overlays, patching, conflict detection, projection, reconciliation. Do *not* hard-code one editorial/sync/conflict/canonical-source policy — keep those configurable.
-- **Union without erasure.** Always preserve provenance: which shard a page came from, its freshness, whether it is cached, whether it has overlays, whether it diverges from an equivalent page elsewhere. Never hide authorship, conflicts, freshness, or backend limitations.
-- **No silent remote mutation.** Do not mutate remote systems without explicit adapter support and user intent.
-- **Graceful degradation.** Limited backends must still be usable as read-only/cache/projection/backup/patch targets.
-- **Not a file-sync daemon.** Synchronization is wiki-page-semantic, not generic file mirroring.
-
-`INTENT.md` has a "Stability Note": changes that redefine what a shard is, Git's role, how root entities are modeled, or whether this is an orchestrator vs. an engine are **architectural changes** and should be rare and deliberate.
-
-## Build, test, run
-
-Python with a `src/` layout, built via hatchling, tested with pytest. Tests run against the source tree directly (`pythonpath = ["src"]` in `pyproject.toml`), so no install/editable step is required to run them.
-
-```bash
-pip install -e ".[dev]"   # one-time: install dev tooling (pytest, pytest-cov, ruff)
-pytest                    # run the full test suite
-pytest tests/test_package.py::test_version_is_exposed  # run a single test
-pytest --cov              # run with coverage
-ruff check                # lint
-ruff format               # format
-```
-
-Note: the system `pytest` is 7.4.x; `minversion` in `pyproject.toml` is pinned to `7.0` to match. Bump it if a newer pytest is installed into the dev environment.
+@SCOPE.md
+@.claude/rules/repo-identity.md
+@.claude/rules/session-protocol.md
+@.claude/rules/first-session.md
+@.claude/rules/workplan-convention.md
+@.claude/rules/stack-and-commands.md
+@.claude/rules/architecture.md
+@.claude/rules/repo-boundary.md
+@.claude/rules/credential-routing.md
+@.claude/rules/agents.md

INTENT.md

@@ -16,6 +16,8 @@ The goal is to allow independently stored and differently implemented wikis, pag
 
 The repository provides a **shard orchestration layer** for interconnected Markdown and markup-based wiki content.
 
+Equivalently, shard-wiki can be used as a **headless, API-first wiki engine** — optimized for **integrating heterogeneous data sources** and for **efficient access by agents and automation** — that ships its own native engine as one (canonical-mode) shard among many. There is no bundled UI: presentation and rendering are consumer concerns.
+
 It allows wiki-like systems to:
 
 * Attach heterogeneous page stores as shards of a shared information space
@@ -30,6 +32,7 @@ It allows wiki-like systems to:
 * Run fully standalone with open read/write access and complete change history, then progressively layer multi-tenant enterprise access control through external identity integration
 * Allow existing wiki engines to become federation-capable through a shared API
 * Allow non-federation-aware systems to participate through adapters and projections
+* Serve as a **headless, API-first wiki engine** (a small typed-extension core) that integrates heterogeneous data sources and is consumed efficiently by agents and automation
 
 It transforms disconnected wiki engines, Git repositories, local folders, WebDAV directories, application-specific content stores, and desktop editing workflows into a **composable federated wiki space**.
 
@@ -85,7 +88,7 @@ A mature `shard-wiki` should allow each participating shard to see the others as
 
 This repository is **not** intended to:
 
-* Replace all wiki engines with a single canonical wiki implementation
+* Replace all wiki engines with a single canonical wiki implementation *(shard-wiki MAY still provide its own native, headless, API-first engine as one optional shard backend — see Design Principles — but never as a mandated or universal replacement)*
 * Force every shard to use the same backend, database, directory layout, or storage format
 * Require every participating system to become federation-aware
 * Require every participating shard to be Git-native
@@ -148,6 +151,9 @@ Policy decisions such as conflict preference, canonical source selection, public
 * **Composable integration**  
   Wiki engines should be able to use the `shard-wiki` API to become federation-enabled without reimplementing federation internally.
 
+* **Native reference engine (additive, headless & API-first)**  
+  shard-wiki MAY provide its own native wiki-engine as a **canonical-mode shard backend** — a **small core** with a **typed-extension framework**, activated **per shard** (only what you need). It is **headless and API-first** (no bundled UI; presentation/rendering are consumer concerns) and tuned for **integrating heterogeneous data sources** and **efficient agent/automation access**. It is *one shard type among many*, implemented against shard-wiki's own adapter contract; it does **not** replace other engines, mandate a single implementation, or change shard-wiki's role as an orchestrator. Shard sovereignty and union-without-erasure are preserved.
+
 * **Open by default, progressively governed**  
   A standalone `shard-wiki` must be runnable with zero external dependencies in a classic Ward Cunningham / c2-style open read/write-for-all mode. Access control is an *additive capability*, not a precondition: the same core progresses — without re-architecture — to authenticated single-user, to group/role-based, to multi-tenant enterprise access control, mirroring the NetKingdom capability ladder (lightweight → expanded).
 
@@ -201,3 +207,5 @@ Such changes should be rare, because they affect all downstream systems relying
 
 In particular, changes that redefine what counts as a shard, what role Git plays, how root entities are modeled, or whether `shard-wiki` is an orchestrator rather than a wiki engine should be treated as architectural changes.
 
+**Amendment — 2026-06-15 (SHARD-WP-0013 T4, decision `84ffdb48`):** admits an **additive** native reference wiki-engine — **headless, API-first**, a small typed-extension core — as a **canonical-mode shard backend** optimized for data-source integration and agent access. Deliberate, narrow scope change; shard-wiki remains an orchestrator and neither mandates nor replaces other engines. (Mirrors the earlier auth-in-core amendment precedent.)
+

SCOPE.md

@@ -17,12 +17,12 @@ Learnings update both SCOPE and INTENT where necessary.
 
 | Layer | State |
 |-------|-------|
-| Code | Python package scaffold (`src/shard_wiki/`, smoke tests only) |
+| Code | Foundation slice implemented (SHARD-WP-0007): `provenance` + `policy` leaves, `model` (Identity/Placement/Span/Page/CapabilityProfile), `adapters` (contract + FolderAdapter + conformance suite), `coordination` (event-sourced DecisionLog), `union` (resolution + chorus, overlay-aware), `InformationSpace` orchestrator. Write path added (SHARD-WP-0008): writable adapter, overlay engine (draft→patch→apply-under-drift), edit() unifies write-through + overlay-before-mutation. Native engine implemented (SHARD-WP-0014): `engine` (kernel + typed-extension runtime + per-shard activation [ADR-0001] + capability-profile-from-extensions + EngineShardAdapter + the `ext.struct` built-in) — an engine shard attaches to an InformationSpace as a canonical-mode shard. Git-backed coordination log (SHARD-WP-0009): `DecisionLog` storage factored behind an `EventStore`; `GitEventStore` makes the log git-addressable (each space a ref, append = immutable CAS-guarded commit), a per-space `AppendAuthority` (lease) gives a single-writer total order with re-grantable HA hand-off, cross-process read-your-writes verified, and a verbatim one-time importer (`migrate_space`/JSONL) replays in-memory logs into git; `InformationSpace.git_backed(...)` wires it. Derived views (SHARD-WP-0010): `views` (wikilink + red-link model, BackLinks, RecentChanges, AllPages/SiteMap) — recomputable, provenance-carrying, presentation-free, exposed via `InformationSpace.backlinks/recent_changes/all_pages/site_map`. Incremental-first derived tier (SHARD-WP-0011): `incremental` (indexed equivalence via MinHash/LSH blocking + verify, change-driven delta maintenance with retraction/propagation, Merkle-style digest + self-healing I-2 consistency-checker, `UnionIndex` routed behind `InformationSpace.all_pages` with rebuild as explicit fallback). Second adapter (SHARD-WP-0012): `GitShardAdapter` — git-IS-store substrate (read=tracked *.md, write=commit, current_rev=per-path sha for drift, adopted git-native history), passes conformance, works across folder+git shards in union/overlay/edit with no core change (capability-as-data proven on a second substrate). 196 tests green, ~97% coverage |
 | Intent | `INTENT.md` established; authorization-in-core amendments drafted |
 | Research | yawex prior art; c2 origins; federation concepts; wikiengines overview (`research/260608-*/`); XWiki/TWiki/Foswiki deep dives (`research/260613-*/`); Xanadu + ZigZag + Roam + Obsidian + Notion + Joplin + Logseq + local-first workspaces (Anytype/AFFiNE/AppFlowy) + Trilium + Wiki.js + Federated Wiki + Wikibase + git-forge wikis + TiddlyWiki + ikiwiki + Quip + MojoMojo + Oddmuse + UseModWiki deep dives & shard-spectrum synthesis (`research/260614-*/`) |
 | Demand | NetKingdom integration asks captured, not yet negotiated |
-| Spec | Architecture blueprint drafted; UseCaseCatalog 84 UCs from research; PRD/TSD scaffolds |
-| Work | `SHARD-WP-0001` active (6 tasks); `SHARD-WP-0002` active (16 tasks: T1–T10 federation + T11–T16 adapter contract); `SHARD-WP-0003` **done** (9 engine dives complete); `SHARD-WP-0004` active (8 computational-knowledge dives: T1 literate programming, T2 Mathematica, T3 Jupyter, T4 Processing, T5 Strudel, T6 Squeak + T8 Pharo (merged), T7 Glamorous Toolkit done — all 8 dives complete) |
+| Spec | CoreArchitectureBlueprint (whole-system, hardened via SHARD-WP-0005/0006) + FederationArchitecture + FederationRequirements + TSD §A adapter contract + ArchitectureBlueprint (auth/history) + WikiEngineCoreArchitecture (headless API-first engine, SHARD-WP-0013) drafted; UseCaseCatalog 84 UCs (+ engine capability-structure layer); PRD scaffold |
+| Work | `SHARD-WP-0001` **done** (6 ADRs: yawex-derived federation requirements → `spec/FederationRequirements.md`); `SHARD-WP-0002` **done** (18 tasks → `FederationArchitecture.md` [T1–T10, T17] + `TechnicalSpecificationDocument.md` §A adapter contract [T11–T16, T18]); `SHARD-WP-0003` **done** (9 engine dives complete); `SHARD-WP-0004` **done** (all 8 computational-knowledge dives T1–T8 complete + "computational page model" synthesis); `SHARD-WP-0005` **done** (9 tasks: CoreArchitectureBlueprint hardened against the 260615 review); `SHARD-WP-0006` **done** (5 tasks: round-2 hardening — overview reconciled, event-sourced coordination + append authority, adapter conformance, incremental correctness + I-2 verification) |
 
 ## In Scope (today)
 
@@ -32,11 +32,15 @@ Learnings update both SCOPE and INTENT where necessary.
 - Authorization model design (delegated authentication, core authorization).
 - Shard adapter contract and wiki page model (to be specified, then implemented).
 - Git-backed coordination journal for information spaces.
+- A **native, headless, API-first wiki-engine core** (small typed-extension core, as a
+  canonical-mode shard backend) — design via SHARD-WP-0013; optimized for data-source
+  integration and agent access.
 - State Hub workplan registration and consistency sync.
 
 ## Out Of Scope (today)
 
-- A standalone wiki engine UI or rendering pipeline.
+- A wiki-engine **UI or rendering pipeline** (the engine is headless/API-first; presentation
+  is a consumer concern). A bundled standalone UI is not provided.
 - Authentication, credential storage, or user directory implementation.
 - Hard-coded editorial, sync, or conflict-resolution policy.
 - Generic file mirroring independent of wiki-page semantics.

history/260615-core-architecture-blueprint-review-2.md

@@ -0,0 +1,91 @@
+# Critical review (round 2) — CoreArchitectureBlueprint.md (hardened)
+
+Date: 2026-06-15 · Reviewer: tegwick (with Claude) · Subject:
+`spec/CoreArchitectureBlueprint.md` after **SHARD-WP-0005** (commit f21b7b5) · Feeds:
+**SHARD-WP-0006**
+
+A second hostile pass over the *hardened* blueprint. Round 1 found design bugs; this round
+finds (a) self-consistency regressions the surgical hardening introduced, and (b) deeper
+second-order gaps — some of which the hardening *sharpened*. Verdict: the architecture is now
+substantially sound; what remains in §B/§C are hard distributed-systems/operational questions,
+not design smells — except §A (a real regression) and three foundational gaps in §B.
+
+---
+
+## A. Self-consistency regressions introduced by surgical hardening
+
+The 9 edits deepened §6–§9 but did not propagate to the **overview surfaces**, so the document
+now contradicts itself between its summary and its body (and readers trust the summary).
+
+- **A-1 (real contradiction).** §4 still says "Addressing, **equivalence**, and transclusion
+  key on identity" — the exact conflation T2 fixed in §7.2 (equivalence keys on *content
+  fingerprint across distinct identities*). → **WP-0006 T1**
+- **A-2.** §4 "Projection — typed on two axes" and §4 "Provenance envelope … every artifact
+  carries [full wrapper]" are stale vs T7's §8.4 (two-axis = extension point; trivial default)
+  and §7.3 (layered effective-vs-own). → **T1**
+- **A-3.** §10 policy surface omits knobs the hardening added (freshness/staleness §8.8,
+  squash-compaction §8.1, conflict-resolution preset §8.6, tenant-partition) — yet §11 defines
+  `policy/` as "owns the §10 surface." The module contract points at a stale list. → **T1**
+- **A-4 (cosmetic).** §3 diagram + §11 header still say "L4 rebuildable cache" / "15 spectra,"
+  advertising the pre-hardening model (§8.7 incremental-first; §6.5 orthogonal-core). → **T1**
+
+Meta-point: surgical editing hardened the body but regressed whole-document coherence; v2
+needs an **overview-reconciliation pass**.
+
+## B. Foundational gaps (serious; some sharpened by the hardening)
+
+- **B-1 — The journal is now a concurrent-write DB, but it's single-writer Git.** §8.6's
+  consistency model assumes "the journal is local Git, read-your-writes." L4 multi-tenant + the
+  L6 Orchestrator API imply a server; HA/scale implies *multiple* instances. Concurrent commits
+  of coordination-canonical state to one git journal = lock contention / merge races; Git is not
+  a concurrent-write store. Either single-writer-per-space (an unstated HA ceiling) or a real
+  concurrent coordination store with Git as an *export*. **T1 of WP-0005 worsened this** by
+  loading more canonical state into the journal. The keystone unanswered question. → **T2**
+- **B-2 — Capability-as-data trusts self-reported profiles with no conformance check.** I-3 +
+  §6.5's degradation contract assume the profile tells the truth. A buggy adapter (claims
+  `merge=git/text`, corrupts; claims `notify`, never emits) silently poisons every degradation
+  decision. No **adapter conformance suite** (declared profile == observed behavior) exists.
+  Foundational for an architecture whose correctness rests on profile accuracy. → **T3**
+- **B-3 — "Coordination-canonical state in the journal" has no representation design.** T1
+  relocated overlays/bindings/aliases/equivalence-sets/merges into "the journal" without saying
+  *how* Git stores structured mutable state. "All equivalences touching X" over a git-of-files
+  is O(scan) unless indexed — and an index is L4/derived. The new central concept is a black
+  box; resolve *with* B-1. → **T2**
+- **B-4 — Incremental equivalence is under-specified/likely incorrect; I-2 only eventually
+  true.** §8.7 re-verifies a changed page's *new* candidate set but not the pairs it *leaves*
+  (a page exiting an LSH bucket can break an existing equivalence edge); the delta is not
+  additive. Deeper: incremental maintenance drifts from `f(canonical)`, so I-2 holds only
+  eventually, guaranteed solely by an expensive reconcile-against-rebuild. Needs a stated
+  verification mechanism (background checker / digest-vs-sampled-rebuild). → **T4**
+
+## C. Real but second-tier (track as open problems O-8…O-11)
+
+- **C-1 — Mechanism-over-policy → operator burden; no preset bundles.** ~7 knob families with
+  sub-modes and interactions; only authz (L0–L4) bundles into personas. Need named bundles
+  ("personal vault" / "team wiki" / "enterprise federation"). → **O-8 / T5**
+- **C-2 — Tenant partitioning (I-13) vs shard sharing + lazy projection.** A shard in two roots
+  is cached twice → duplicate storage + double refresh on rate-limited backends. Shard
+  exclusive-to-one-root or shareable? Unresolved. → **O-9 / T5**
+- **C-3 — Span-level authz + transclusion is an unmodeled leak path.** Authz is per
+  page/shard/tenant; transclusion crosses shards at span granularity → a page can leak a span
+  past its ACL (aggregation/inference). §7.3's ⊕ also stops being simple two-level inheritance
+  across a transclusion boundary. → **O-10 / T5**
+- **C-4 — Union-under-unavailability undefined.** Freshness covers *stale*, nothing covers
+  *down*. The dead-shard read path (partial union? error? last-known?) is unspecified though
+  it's the commonest real failure. → **O-11 / T5**
+
+## D. Recommended resolution (→ SHARD-WP-0006)
+
+1. **§A reconciliation** (T1) — make the overview match the hardened body.
+2. **Journal & coordination-state model** (T2) — settle single-vs-multi-writer and separate the
+   **coordination-state store** from the **content-history journal**. Likely resolution:
+   **event-sourced coordination** — an append-only *decision log* is the coordination-canonical
+   tier (git-addressable, I-6 preserved); the queryable current state (alias table, equivalence
+   set) is a *derived fold* of the log (disposable). Append-logs tolerate concurrency far better
+   than mutable-file Git; state a concurrency model. Resolves **B-1 + B-3** together.
+3. **Adapter conformance suite** (T3) — make a passing conformance run part of the contract
+   (B-2): every adapter proves declared profile == observed behavior.
+4. **Incremental correctness + I-2 verification** (T4) — fix the leaving-bucket re-verification
+   and propagation; add a background consistency-checker / derived-tier digest so I-2 is
+   verifiable, not merely asserted (B-4).
+5. **Track §C** (T5) — O-8…O-11 with chosen direction + revisit trigger; close-out.

history/260615-core-architecture-blueprint-review.md

@@ -0,0 +1,122 @@
+# Critical review — CoreArchitectureBlueprint.md
+
+Date: 2026-06-15 · Reviewer: tegwick (with Claude) · Subject:
+`spec/CoreArchitectureBlueprint.md` @ commit **9b5b393** · Feeds: **SHARD-WP-0005**
+
+A deliberately hostile review of the first whole-system architecture, to find where it
+**breaks (correctness)**, **fails to scale**, and **could be more elegant/efficient** before
+any implementation. Findings are prioritised; each is the input to a SHARD-WP-0005 task.
+
+## Verdict in one line
+
+The **layering and the dual narrow waist are sound and stay**. The **thesis is ~90% right**;
+the missing 10% (curatorial / coordination-canonical state) breaks its clean story. There are
+**two genuine bugs**, **two large unaddressed scaling risks**, and several **elegance/efficiency
+debts** — all fixable without touching INTENT.
+
+---
+
+## A. The framing crack (fix resolves three issues)
+
+**A-1 — Two buckets hide a third.** The thesis "canonical at the edges, derived in the middle"
+omits **born-in-the-middle-but-canonical** state: overlays that are the local truth against a
+read-only shard (Flow C), manual **curator equivalence bindings**, alias tables, merge
+decisions. These encode human judgment or local-only content and **cannot be rebuilt** from
+shards+journal.
+
+**Contradiction:** I-2 declares L4 rebuildable, yet §8.4 puts "alias table, curator binding"
+in L4. You cannot rebuild a curator's manual binding.
+
+**Fix:** three states — **sharded-canonical**, **coordination-canonical** (journal: overlays,
+bindings, aliases, merges — durable, born in the middle), **derived-disposable** (union graph,
+indexes, projections). Re-frame §1 as **canonical (sharded + coordination) vs derived
+(disposable)**; `derived = f(canonical)` then becomes actually true. → **T1**
+
+---
+
+## B. Where it breaks (correctness)
+
+**B-1 — Identity conflated with content-fingerprint (BUG).** §7.2 derives page identity from
+content fingerprint. That makes **editing a page change its identity**, breaking every
+reference. Fingerprints identify *versions/equivalence*, not *identity*. Page identity must be
+a **stable handle (uid)** surviving edits; fingerprints belong to the **equivalence** mechanism
+(§8.4). One word, two concepts, wrong implementation for the stable one. → **T2**
+
+**B-2 — No concurrency/consistency model.** Concurrent overlays on one page, overlay applied
+after source drift, journal-commit vs shard-native-write ordering — all undefined. Conflict
+handling is deferred to "policy presets," but **conflict *detection + representation* is core
+mechanism**; only *resolution* is policy. The union's consistency guarantee is unstated
+(eventually-consistent? read-your-writes? causal-via-journal?). → **T3**
+
+**B-3 — Persisted union cache + multi-tenant = leak surface.** §13 recommends a persisted L4
+cache; §9 protects content by *read-time* filtering on the provenance envelope. A persisted
+cross-tenant union cache guarded only by read-time filtering is an L4 attack surface. Tension
+between I-2 (persisted rebuildable cache), scale, and L5 isolation is unacknowledged. → **T8**
+
+---
+
+## C. Where it fails to scale
+
+**C-1 — Equivalence detection is O(N²), no indexing/incremental story.** Fingerprint /
+span-set-overlap across all pages of all shards is combinatorial (10 shards × 100k pages ≈
+10¹² comparisons). No blocking/LSH/indexing, no incremental maintenance. Biggest scaling
+hazard in the document. → **T4**
+
+**C-2 — "Rebuildable cache" collides with the operational-envelope axis.** A byte-exact
+rebuild requires reading *every page of every shard*, including rate-limited/paginated
+external APIs (Notion) and irreducibly-live sources — hours-to-days. I-2 contradicts axis-10.
+**Incremental, change-driven maintenance must be primary** (notify→delta), rebuild a rare
+fallback. Cache invalidation — the actual hard problem — is named once and never designed. →
+**T4, T5**
+
+**C-3 — Unbounded history at open L0 = DoS/perf.** "Every write a commit" + "open for all" ⇒
+the git journal grows without bound under bots/vandalism and git degrades on huge histories.
+"History is the floor" has an unacknowledged cost: packing, compaction, per-shard offload. →
+**T8**
+
+---
+
+## D. Elegance / efficiency debts
+
+**D-1 — The 15 spectra assert a clean degradation function never demonstrated.** Either most
+axes are irrelevant to most ops (then the 15-D profile is ceremony), or behavior depends on
+several axes *jointly* (then "no per-backend code" becomes a sprawling axis-interaction matrix
+— the flat-checklist problem in higher dimensions). And the axes **aren't orthogonal**
+(git-native history ⟺ git-IS-store ⟺ git/text merge; encrypted opacity ⟹ query/translation
+collapse). Model a **smaller orthogonal core** + **derived/implied** positions, and state the
+**axis-interaction subset** the degradation logic truly uses. → **T6**
+
+**D-2 — Provenance envelope isn't inherited; it'll dwarf the content.** Per-span envelopes at
+block granularity = 10k near-identical envelopes for a 10k-block graph. The doc already
+invented the right pattern for Trilium ("effective-vs-own with per-attribute provenance") and
+failed to apply it to its own envelope. Make provenance **layered (page envelope + span
+deltas)**. → **T7**
+
+**D-3 — Projection machinery over-fit to the exotic tail.** Two-axis model + three facets +
+view registry exist mostly for UC-83/84 (2 of 84 UCs); the 95% case (markdown in git) pays the
+weight. Make the **common case trivial** (default = plain lazy replication) and
+derivation/liveness an **extension point**, not a taxonomy every projection instantiates. →
+**T7**
+
+**D-4 — Cross-cutting rails are the highest-coupling components, presented as clean.**
+`provenance/` and capability types are imported by every layer (god-modules); an envelope
+change ripples everywhere. And **policy has no module** (§10 enumerates it; §11 omits it)
+despite being consulted by L3/L4/L5. Give policy a home; pin the rails behind stable narrow
+interfaces. → **T7**
+
+---
+
+## E. What explicitly stays
+
+- The 6-layer model + the dual narrow waist (adapter contract / page model).
+- Capability-as-data (I-3), union-without-erasure (I-4), overlay-before-mutation (I-5),
+  Git-addressable coordination (I-6), mechanism-over-policy (I-7), graceful degradation (I-8).
+- The federation-model taxonomy and the auth ladder (ArchitectureBlueprint.md).
+
+## F. Disposition
+
+Some findings are **solvable now** (A-1, B-1, D-2, D-3, D-4, C-3); some are **partially open**
+and should be tracked honestly rather than pretend-solved (B-2 consistency model: pick a
+guarantee; C-1 equivalence-at-scale: pick a blocking strategy; D-1 axis interactions: enumerate
+the real subset). SHARD-WP-0005 closes the solvable ones and records the open ones in a new
+"Known scaling risks & open problems" section of the blueprint. → **T9**

history/260615-reuse-surface-contributions.md

@@ -0,0 +1,45 @@
+# reuse-surface contributions — shard-wiki (SHARD-WP-0013 T3)
+
+Date: 2026-06-15 · From: shard-wiki (whynot) · To: reuse-surface (helix_forge) · Tracked list
+of (A) capabilities shard-wiki registered, (B) **gaps** shard-wiki proposes the reuse surface
+add, and (C) capabilities shard-wiki will **consume** rather than rebuild. Communicated to the
+reuse-surface agent via state-hub `send_message`.
+
+## A. Registered (T1 + T3) — 8 entries
+
+`capability.wiki.{shard-orchestration, adapter-contract, page-model, coordination-journal,
+overlay, federation-models, engine-typed-extensions, derived-views}` — committed in
+reuse-surface, `validate` ok (20 entries total).
+
+## B. Proposed gaps (cross-cutting; not shard-wiki-internal) → reuse-surface should own/define
+
+- **G1 — `capability.platform.typed-extension-framework`** *(suggested)*
+  A reusable pattern: a **small core + a stringent typed-extension framework** where extensions
+  declare typed contracts, compose, and are **activated per context**. shard-wiki's wiki engine
+  (`capability.wiki.engine-typed-extensions`) is one instance, but the *pattern* is
+  cross-domain (any HelixForge capability platform). Evidence: shard-wiki UseCaseCatalog
+  "Capability structure" layer (core + 10 typed extensions + conflict-mediation map).
+  Suggested owner: helix_forge / reuse-surface. Relation: would `generalize`
+  `capability.wiki.engine-typed-extensions`.
+
+- **G2 — `capability.content.translation-fidelity`** *(suggested)*
+  Lossless/lossy **content translation with an explicit fidelity report** (what round-trips
+  cleanly vs degrades, non-mappable elements preserved as provenance). Reusable well beyond
+  wiki (any format-bridging consumer). Evidence: shard-wiki TSD §A.6, UC-42/UC-59.
+
+## C. Consumptions (reuse, do not rebuild)
+
+- **`capability.feature-control.evaluate`** (helix_forge/feature-control) → shard-wiki's
+  **per-shard extension/feature activation** (the "activate only what you need" mechanism).
+  Already recorded as a relation on `capability.wiki.engine-typed-extensions`.
+- **`capability.authorization.policy-evaluate`** (flex-auth) → shard-wiki's **X-AUTHZ** policy
+  decisions. shard-wiki owns the authz *model* (authz-in-core) but can reuse this evaluation
+  engine rather than building one.
+- **`capability.statehub.{progress-log, workstream-coordinate}`** → already in use for
+  coordination across this work.
+
+## Status
+
+Gaps G1/G2 are **suggestions** to the reuse-surface owner (not unilateral registrations, since
+they are cross-cutting, not shard-wiki-internal). Consumptions are recorded for the engine
+architecture (T5) so it reuses rather than reinvents.

history/README.md

@@ -1,8 +1,19 @@
 # history/
 
-Archived material that is no longer needed for daily work but should be kept.
+Archived material and the project's **meta-history**: finished/canceled workplans kept for
+the record, plus durable **reviews, critical assessments, and decision records** — the
+reasoning behind the specs, captured at a point in time.
 
-Use a `yymmdd-` prefix when archiving files or directories. Content here is
-**out of scope** for regular tasks — consult only for research or diagnostics.
+Use a `yymmdd-` prefix. Archived material is **out of scope** for regular tasks (consult only
+for research or diagnostics); assessment/review records are point-in-time and may seed active
+workplans, but are not edited after the fact — supersede with a new dated record and link back.
 
-Finished or canceled workplans from `workplans/` are archived here.
+Distinct from the **coordination journal** (a runtime Git-backed record of *content* change
+flows inside an information space, an INTENT domain concept); `history/` is the *project's own*
+design evolution.
+
+| Date | Record | Subject |
+|------|--------|---------|
+| 2026-06-15 | `260615-core-architecture-blueprint-review.md` | Critical review of `spec/CoreArchitectureBlueprint.md` (commit 9b5b393); inputs to `SHARD-WP-0005` |
+| 2026-06-15 | `260615-core-architecture-blueprint-review-2.md` | Round-2 review of the hardened blueprint (post-`SHARD-WP-0005`, f21b7b5); inputs to `SHARD-WP-0006` |
+| 2026-06-15 | `260615-reuse-surface-contributions.md` | shard-wiki's reuse-surface registrations, proposed gaps (G1/G2), and consumptions (`SHARD-WP-0013` T3) |

pyproject.toml

@@ -36,6 +36,11 @@ pythonpath = ["src"]
 branch = true
 source = ["shard_wiki"]
 
+[tool.coverage.report]
+show_missing = true
+# Quality floor for `pytest --cov` / `coverage report` (not forced on a bare `pytest` run).
+fail_under = 90
+
 [tool.ruff]
 src = ["src", "tests"]
 target-version = "py311"

registry/README.md

@@ -0,0 +1,12 @@
+# Capability Registry
+
+Markdown-first capability index for federation and reuse planning.
+
+## Authoring
+
+1. Copy a capability entry template (see reuse-surface `templates/capability-entry.template.md`).
+2. Add the row to `indexes/capabilities.yaml`.
+3. Run `reuse-surface validate` from a checkout with the CLI installed.
+4. Merge to `main` and verify publish with `reuse-surface establish --publish-check`.
+
+Federation contract: reuse-surface `docs/RegistryFederation.md`.

registry/capabilities/capability.wiki.adapter-contract.md

@@ -0,0 +1,103 @@
+---
+id: capability.wiki.adapter-contract
+name: Capability-Aware Shard Adapter Contract
+summary: A versioned backend interface where each binding declares a verified capability profile (positions on capability spectra), so federation ops degrade by capability.
+owner: shard-wiki
+status: draft
+domain: helix_forge
+tags: [wiki, adapter, capability, contract, conformance, shard-wiki]
+
+maturity:
+  discovery:
+    current: D5
+    target: D6
+    confidence: high
+    rationale: >
+      Fifteen capability spectra with an orthogonal core + implication rules, plus
+      a normative contract spec (TSD Section A); derived from a ~23-system synthesis.
+  availability:
+    current: A2
+    target: A5
+    confidence: medium
+    rationale: >
+      AdapterContract + a read/write FolderAdapter + a conformance suite that
+      verifies declared profile == observed behaviour exist as a source module.
+
+external_evidence:
+  completeness:
+    level: C2
+    name: Partial
+    confidence: medium
+    basis: scope_vs_intent_and_consumer_expectations
+    satisfied_expectations:
+      - versioned interface with declared, conformance-verified capability profiles
+      - one concrete adapter (file-store) passes the conformance suite
+    broken_expectations:
+      - only one substrate implemented (git-IS-store, REST, CRDT adapters planned)
+    out_of_scope_expectations:
+      - hosting backends
+  reliability:
+    level: R1
+    confidence: low
+    basis: consumer_quality_signals
+    known_reliability_risks:
+      - single adapter implemented so far
+
+discovery:
+  intent: >
+    Mediate heterogeneity at one narrow waist: a backend participates by implementing a
+    versioned interface and declaring a verified position on each capability spectrum.
+  includes:
+    - capability profile as data (orthogonal-core spectra + implied positions)
+    - operation verbs (read/write/diff/merge/notify/.../derive-projection/execute)
+    - a conformance suite (profiles verified, not self-asserted)
+  excludes:
+    - assuming uniform backend capabilities
+  use_cases:
+    - "shard-wiki UseCaseCatalog UC-34..UC-43, UC-50, UC-57, UC-60..UC-69 (shard attachment & adapter binding)"
+
+availability:
+  current_level: A2
+  target_level: A5
+  current_artifacts:
+    - "shard-wiki/src/shard_wiki/adapters/"
+  consumption_modes:
+    - source module
+
+relations:
+  depends_on:
+    - capability.wiki.page-model
+  supports:
+    - capability.wiki.shard-orchestration
+
+evidence:
+  documentation:
+    - "shard-wiki/spec/TechnicalSpecificationDocument.md (Section A)"
+    - "shard-wiki/spec/CoreArchitectureBlueprint.md (Section 6)"
+  tests:
+    - "shard-wiki/tests/test_folder_adapter.py"
+    - "shard-wiki/tests/test_conformance.py"
+
+consumer_guidance:
+  recommended_for:
+    - exposing any page store as a capability-described, conformance-checked shard
+  not_recommended_for:
+    - backends that cannot honestly describe their capabilities
+  known_limitations:
+    - reference implementation covers the file-store substrate only so far
+---
+
+# Capability-Aware Shard Adapter Contract
+
+The bottom narrow waist of shard-wiki: a versioned interface plus a **verified** capability
+profile per binding. Core logic is written once against capabilities (not per-backend), and
+the conformance suite rejects profiles whose declared abilities don't match observed behaviour.
+
+## Assessment notes
+
+### Discovery
+Fifteen spectra reduced to an orthogonal core with implication rules (CoreArchitectureBlueprint
+Section 6.5); normative in TSD Section A.
+
+### Availability
+`adapters/` ships the contract, a folder adapter, and `assert_conformant`.

registry/capabilities/capability.wiki.coordination-journal.md

@@ -0,0 +1,103 @@
+---
+id: capability.wiki.coordination-journal
+name: Event-Sourced Coordination Journal
+summary: An append-only, totally-ordered-per-space decision log (overlays, bindings, aliases, merges, forks) whose current state is a derived fold; git-addressable history.
+owner: shard-wiki
+status: draft
+domain: helix_forge
+tags: [wiki, event-sourcing, coordination, git, journal, shard-wiki]
+
+maturity:
+  discovery:
+    current: D5
+    target: D6
+    confidence: high
+    rationale: >
+      Keystone resolved across two architecture reviews: coordination-canonical state
+      as an append-only decision log with a per-space append authority; current state
+      is a derived fold (derived = f(log)).
+  availability:
+    current: A2
+    target: A4
+    confidence: medium
+    rationale: >
+      In-memory DecisionLog + fold work as a source module; the git-backed store with a
+      per-space lease (the production backing) is planned.
+
+external_evidence:
+  completeness:
+    level: C2
+    name: Partial
+    confidence: medium
+    basis: scope_vs_intent_and_consumer_expectations
+    satisfied_expectations:
+      - append-only, totally-ordered-per-space log with read-your-writes
+      - derived fold to aliases + transitively-merged equivalence groups
+    broken_expectations:
+      - git-backed storage and per-space lease/append-authority not yet implemented
+    out_of_scope_expectations:
+      - general-purpose event bus
+  reliability:
+    level: R1
+    confidence: low
+    basis: consumer_quality_signals
+    known_reliability_risks:
+      - in-memory backing only; cross-process durability pending
+
+discovery:
+  intent: >
+    Make coordination-canonical decisions durable and git-addressable as events, with the
+    queryable current state always recomputable by replay.
+  includes:
+    - append-only decision log, totally ordered per information space
+    - derived fold to current coordination state (aliases, equivalence groups, overlays)
+    - per-space append authority (concurrency model)
+  excludes:
+    - storing derived/disposable union state
+  use_cases:
+    - "shard-wiki UseCaseCatalog UC-29, UC-33 (history, attribution, coordination journal)"
+
+availability:
+  current_level: A2
+  target_level: A4
+  current_artifacts:
+    - "shard-wiki/src/shard_wiki/coordination/decision_log.py"
+  target_artifacts:
+    - git-backed log store with per-space lease
+  consumption_modes:
+    - source module
+
+relations:
+  supports:
+    - capability.wiki.shard-orchestration
+    - capability.wiki.overlay
+
+evidence:
+  documentation:
+    - "shard-wiki/spec/CoreArchitectureBlueprint.md (Section 8.1)"
+  tests:
+    - "shard-wiki/tests/test_decision_log.py"
+
+consumer_guidance:
+  recommended_for:
+    - durable, replayable, git-addressable coordination state for a federated space
+  not_recommended_for:
+    - high-frequency general event streaming
+  known_limitations:
+    - production git backing + lease are still on the roadmap (SHARD-WP-0009)
+---
+
+# Event-Sourced Coordination Journal
+
+The keystone: coordination-canonical state (overlays, equivalence bindings, aliases, merges,
+forks) is an append-only **decision log**, totally ordered per information space; the queryable
+current state is a derived **fold** of the log (`derived = f(log)`). The log is git-addressable,
+giving history/patch/review/backup for coordination decisions for free.
+
+## Assessment notes
+
+### Discovery
+Resolved across the round-1/round-2 architecture reviews (CoreArchitectureBlueprint Section 8.1).
+
+### Availability
+`decision_log.py` ships an in-memory, totally-ordered log + fold; git+lease backing is planned.

registry/capabilities/capability.wiki.derived-views.md

@@ -0,0 +1,87 @@
+---
+id: capability.wiki.derived-views
+name: Wiki Derived Views
+summary: Recomputable views over a wiki union — BackLinks, RecentChanges, AllPages, SiteMap, and (delegate-or-derive) Search — carrying provenance.
+owner: shard-wiki
+status: draft
+domain: helix_forge
+tags: [wiki, derived-views, backlinks, recentchanges, search, shard-wiki]
+
+maturity:
+  discovery:
+    current: D3
+    target: D5
+    confidence: medium
+    rationale: >
+      Core-vs-adapter classification and behaviours are decided (FederationRequirements ADR-03);
+      implementation is planned (SHARD-WP-0010), not built.
+  availability:
+    current: A0
+    target: A4
+    confidence: low
+    rationale: >
+      Designed; no implementation yet. Informational/planning reuse only today.
+
+external_evidence:
+  completeness:
+    level: C0
+    name: Absent
+    confidence: low
+    basis: scope_vs_intent_and_consumer_expectations
+    satisfied_expectations: []
+    broken_expectations:
+      - no derived view is implemented yet
+    out_of_scope_expectations:
+      - presentation / rendering of views
+  reliability:
+    level: R0
+    confidence: low
+    basis: consumer_quality_signals
+    known_reliability_risks:
+      - planning-stage
+
+discovery:
+  intent: >
+    Provide recomputable, provenance-carrying views over the union (link graph, change feed,
+    enumeration, search) without introducing canonical state.
+  includes:
+    - BackLinks (link graph), RecentChanges (journal + shard signals), AllPages, SiteMap
+    - Search as delegate-to-native-or-derive-index
+  excludes:
+    - view presentation / UI
+  use_cases:
+    - "shard-wiki UseCaseCatalog UC-17..UC-21, UC-63"
+
+availability:
+  current_level: A0
+  target_level: A4
+  current_artifacts:
+    - "shard-wiki/workplans/SHARD-WP-0010-derived-views.md"
+  consumption_modes:
+    - informational
+
+relations:
+  depends_on:
+    - capability.wiki.shard-orchestration
+    - capability.wiki.page-model
+  related_to:
+    - capability.wiki.engine-typed-extensions
+
+evidence:
+  documentation:
+    - "shard-wiki/spec/FederationRequirements.md (ADR-03)"
+
+consumer_guidance:
+  recommended_for:
+    - planning derived navigation/discovery over a federated wiki union
+  not_recommended_for:
+    - implementation reuse today (planning-stage)
+  known_limitations:
+    - not implemented; Search ranking policy undecided
+---
+
+# Wiki Derived Views
+
+Recomputable views over the union (BackLinks, RecentChanges, AllPages, SiteMap, Search). All
+are derived/disposable (no canonical state) and carry provenance; Search is delegate-to-native
+where a shard's query capability allows, else a derived index. Planned in SHARD-WP-0010.

registry/capabilities/capability.wiki.engine-typed-extensions.md

@@ -0,0 +1,115 @@
+---
+id: capability.wiki.engine-typed-extensions
+name: Wiki Engine with Typed Extensions
+summary: A small-core wiki engine realizing a stringent typed-extension framework that addresses all wiki use cases and lets each shard activate only the features it needs.
+owner: shard-wiki
+status: draft
+domain: helix_forge
+tags: [wiki, engine, typed-extensions, feature-activation, shard-wiki]
+
+maturity:
+  discovery:
+    current: D3
+    target: D5
+    confidence: medium
+    rationale: >
+      Architecture authored (shard-wiki/spec/WikiEngineCoreArchitecture.md): small page-store
+      kernel + typed-extension framework, per-shard activation, engine-as-canonical-mode-shard,
+      and a conflict-mediation realization are explored. Detailed extension SDK/ABI and the API
+      protocol remain (so D3 Explored, not yet D4/D5).
+  availability:
+    current: A0
+    target: A4
+    confidence: low
+    rationale: >
+      Planned. No engine kernel or extensions exist yet; informational/planning reuse only.
+
+external_evidence:
+  completeness:
+    level: C0
+    name: Absent
+    confidence: low
+    basis: scope_vs_intent_and_consumer_expectations
+    satisfied_expectations: []
+    broken_expectations:
+      - engine core and typed-extension mechanism not yet designed in detail
+    out_of_scope_expectations:
+      - replacing other wiki engines or mandating one implementation
+  reliability:
+    level: R0
+    confidence: low
+    basis: consumer_quality_signals
+    known_reliability_risks:
+      - planning-stage capability
+
+discovery:
+  intent: >
+    Provide shard-wiki's reference first-party shard backend: a small core + a stringent
+    typed-extension framework covering all collected use cases, mediating conflicting
+    requirements into an integrated whole, with per-shard activation (only what you need).
+  includes:
+    - a minimal engine kernel (page lifecycle, storage via the adapter contract, the typing mechanism)
+    - typed extensions that declare contracts and compose
+    - per-shard feature activation
+  excludes:
+    - replacing or mandating other wiki engines (it is one shard type among many)
+    - a single canonical implementation for all wikis
+  use_cases:
+    - "shard-wiki UseCaseCatalog UC-08..UC-25 and the full catalog (the engine must cover all)"
+
+availability:
+  current_level: A0
+  target_level: A4
+  current_artifacts:
+    - "shard-wiki/workplans/SHARD-WP-0013-wiki-engine-prep.md"
+    - "shard-wiki/spec/WikiEngineCoreArchitecture.md"
+  consumption_modes:
+    - informational
+
+relations:
+  depends_on:
+    - capability.wiki.adapter-contract
+    - capability.wiki.page-model
+  related_to:
+    - capability.feature-control.evaluate
+    - capability.authorization.policy-evaluate
+
+evidence:
+  documentation:
+    - "shard-wiki/workplans/SHARD-WP-0013-wiki-engine-prep.md"
+
+consumer_guidance:
+  recommended_for:
+    - planning a composable, feature-activatable native wiki engine
+  not_recommended_for:
+    - implementation reuse today (planning-stage)
+  known_limitations:
+    - architecture authored; extension SDK/ABI + API protocol still to design; not yet built
+
+promotion_history:
+  - date: "2026-06-15"
+    dimension: discovery
+    from: D2
+    to: D3
+    rationale: WikiEngineCoreArchitecture.md authored (kernel + typed-extension framework explored); INTENT amendment ratified.
+    author: shard-wiki
+---
+
+# Wiki Engine with Typed Extensions
+
+shard-wiki's planned reference first-party shard backend — a *canonical-mode shard* it
+implements natively: a small core plus a stringent typed-extension framework addressing all
+collected use cases, mediating conflicting requirements into a consistent whole, with per-shard
+activation (activate only what you need). It is one shard type among many — not a replacement
+for other engines. Per-shard activation is a candidate consumer of
+`capability.feature-control.evaluate`.
+
+## Assessment notes
+
+### Discovery
+Architecture authored: `shard-wiki/spec/WikiEngineCoreArchitecture.md` (small kernel +
+typed-extension framework; engine = canonical-mode shard). INTENT amendment ratified
+(2026-06-15, decision 84ffdb48). Extension SDK/ABI + API protocol are the next deliverables.
+
+### Availability
+Planning-stage; informational reuse only.

registry/capabilities/capability.wiki.federation-models.md

@@ -0,0 +1,97 @@
+---
+id: capability.wiki.federation-models
+name: Selectable Federation-Model Taxonomy
+summary: Federation as a plural, composable coordination axis (fork+journal, VCS-replication+ping, query-time graph-join, feed, activity-streams, engine-mirror) selected per space.
+owner: shard-wiki
+status: draft
+domain: helix_forge
+tags: [wiki, federation, taxonomy, composable, shard-wiki]
+
+maturity:
+  discovery:
+    current: D4
+    target: D6
+    confidence: high
+    rationale: >
+      A six-model taxonomy distilled from a ~23-system synthesis, each model anchored in a
+      real system, with capability prerequisites and per-space/per-shard composition rules.
+  availability:
+    current: A0
+    target: A4
+    confidence: low
+    rationale: >
+      Designed and specified (FederationArchitecture T17) but not implemented; informational
+      reuse only today.
+
+external_evidence:
+  completeness:
+    level: C1
+    name: Sparse
+    confidence: low
+    basis: scope_vs_intent_and_consumer_expectations
+    satisfied_expectations:
+      - the model taxonomy and selection/composition rules are documented
+    broken_expectations:
+      - no federation transport is implemented yet
+    out_of_scope_expectations:
+      - mandating a single federation mechanism
+  reliability:
+    level: R0
+    confidence: low
+    basis: consumer_quality_signals
+    known_reliability_risks:
+      - design-stage; no runtime evidence
+
+discovery:
+  intent: >
+    Treat federation as selectable and composable rather than one mechanism, so each space
+    picks fork+journal, VCS-replication, query-join, feed, activity-streams, or engine-mirror.
+  includes:
+    - the six federation models + their capability floors
+    - per-space selection and per-shard composition
+  excludes:
+    - imposing one homogeneous federation network
+  use_cases:
+    - "shard-wiki UseCaseCatalog UC-26, UC-31, UC-33, UC-71, UC-72, UC-74, UC-79"
+
+availability:
+  current_level: A0
+  target_level: A4
+  current_artifacts:
+    - "shard-wiki/spec/FederationArchitecture.md (T17)"
+  consumption_modes:
+    - informational
+
+relations:
+  depends_on:
+    - capability.wiki.shard-orchestration
+    - capability.wiki.coordination-journal
+
+evidence:
+  documentation:
+    - "shard-wiki/spec/FederationArchitecture.md"
+    - "shard-wiki/research/260614-shard-spectrum-synthesis/findings.md"
+
+consumer_guidance:
+  recommended_for:
+    - planning a federation strategy that mixes models per source
+  not_recommended_for:
+    - implementation reuse today (design-stage)
+  known_limitations:
+    - no transport implemented; informational planning reuse only
+---
+
+# Selectable Federation-Model Taxonomy
+
+Federation is plural and composable: fork+journal (Federated Wiki), VCS-replication+ping
+(ikiwiki), query-time graph-join (Wikibase SERVICE), feed aggregation, activity streams
+(ActivityPub), and engine-mirror (Wiki.js). A space selects a model and composes per shard;
+the default is fork+journal over git. Design-stage capability — strong for planning reuse.
+
+## Assessment notes
+
+### Discovery
+FederationArchitecture T17, distilled from the shard-spectrum synthesis (v3).
+
+### Availability
+Specified, not implemented — informational reuse only.

registry/capabilities/capability.wiki.overlay.md

@@ -0,0 +1,102 @@
+---
+id: capability.wiki.overlay
+name: Overlay-Before-Mutation Write Path
+summary: Non-destructive edits (draft -> patch -> apply-under-drift) that let read-only, rate-limited, or lossy backends be edited safely without silent remote mutation.
+owner: shard-wiki
+status: draft
+domain: helix_forge
+tags: [wiki, overlay, patch, write-path, conflict, shard-wiki]
+
+maturity:
+  discovery:
+    current: D5
+    target: D6
+    confidence: high
+    rationale: >
+      Overlay lifecycle and apply-under-drift semantics are specified (ADR-05, blueprint
+      Section 8.6) and implemented as a single principled write path.
+  availability:
+    current: A2
+    target: A4
+    confidence: medium
+    rationale: >
+      OverlayEngine (draft/patch/apply), writable adapter, and InformationSpace.edit
+      exist as a source module; three-way merge is not (refuse-on-drift only).
+
+external_evidence:
+  completeness:
+    level: C2
+    name: Partial
+    confidence: medium
+    basis: scope_vs_intent_and_consumer_expectations
+    satisfied_expectations:
+      - draft -> patch -> apply with fast-forward / refuse-on-drift / keep-draft outcomes
+      - no silent remote mutation; overlay_state surfaced in provenance
+    broken_expectations:
+      - three-way / auto merge not implemented (refuse-on-conflict only)
+    out_of_scope_expectations:
+      - federation propagation of applied overlays
+  reliability:
+    level: R1
+    confidence: low
+    basis: consumer_quality_signals
+    known_reliability_risks:
+      - early implementation; conflict handling is detect-and-refuse only
+
+discovery:
+  intent: >
+    Make any sub-write-through backend editable safely: an edit is an overlay first, applied
+    only on explicit intent and only when the source has not drifted.
+  includes:
+    - overlay drafts recorded as coordination-canonical events
+    - patch rendering (unified diff)
+    - apply-under-drift (fast-forward / refuse / keep-draft)
+  excludes:
+    - destructive write without drift check
+  use_cases:
+    - "shard-wiki UseCaseCatalog UC-04, UC-26, UC-29 (remix primitives, overlay)"
+
+availability:
+  current_level: A2
+  target_level: A4
+  current_artifacts:
+    - "shard-wiki/src/shard_wiki/coordination/overlay.py"
+    - "shard-wiki/src/shard_wiki/coordination/patch.py"
+  consumption_modes:
+    - source module
+
+relations:
+  depends_on:
+    - capability.wiki.coordination-journal
+    - capability.wiki.adapter-contract
+
+evidence:
+  documentation:
+    - "shard-wiki/spec/FederationRequirements.md (ADR-05)"
+    - "shard-wiki/spec/CoreArchitectureBlueprint.md (Section 8.2, 8.6)"
+  tests:
+    - "shard-wiki/tests/test_apply.py"
+    - "shard-wiki/tests/test_write_path_integration.py"
+
+consumer_guidance:
+  recommended_for:
+    - safe editing over read-only / rate-limited / lossy backends
+  not_recommended_for:
+    - workflows needing automatic conflict resolution today
+  known_limitations:
+    - merge is detect-and-refuse; three-way merge is future work
+---
+
+# Overlay-Before-Mutation Write Path
+
+One principled write path: every edit drafts an overlay (a coordination-canonical event),
+renders as a patch, and applies under drift checks — fast-forwarding a writable target,
+keeping a local draft on a read-only target, and refusing (never clobbering) on external drift.
+
+## Assessment notes
+
+### Discovery
+Specified in FederationRequirements ADR-05 and CoreArchitectureBlueprint Section 8.2/8.6.
+
+### Availability
+`overlay.py` + `patch.py` + `InformationSpace.edit` ship the path; built in SHARD-WP-0008.

registry/capabilities/capability.wiki.page-model.md

@@ -0,0 +1,104 @@
+---
+id: capability.wiki.page-model
+name: Backend-Neutral Wiki Page Model
+summary: A Markdown-first but stretchable page model with stable identity separate from placement and layered provenance, spanning prose to typed-graph and computational shapes.
+owner: shard-wiki
+status: draft
+domain: helix_forge
+tags: [wiki, page-model, identity, provenance, markdown, shard-wiki]
+
+maturity:
+  discovery:
+    current: D5
+    target: D6
+    confidence: high
+    rationale: >
+      Page shapes (prose, typed records, typed-graph, inline-embedded, non-Markdown,
+      and four computational shapes) plus identity != placement and layered provenance
+      are specified and grounded in the dive research.
+  availability:
+    current: A2
+    target: A5
+    confidence: medium
+    rationale: >
+      Identity/Placement/Span/Page and layered ProvenanceEnvelope exist as a source
+      module; richer shapes (typed-graph, notebook) are modeled but not all built.
+
+external_evidence:
+  completeness:
+    level: C2
+    name: Partial
+    confidence: medium
+    basis: scope_vs_intent_and_consumer_expectations
+    satisfied_expectations:
+      - stable identity distinct from placement and from content fingerprint
+      - layered (effective-vs-own) provenance with near-zero per-span cost
+    broken_expectations:
+      - non-prose shapes (typed-graph, notebook, inline-embedded) not fully realized
+    out_of_scope_expectations:
+      - rendering / presentation
+  reliability:
+    level: R1
+    confidence: low
+    basis: consumer_quality_signals
+    known_reliability_risks:
+      - prose shape is the only exercised path so far
+
+discovery:
+  intent: >
+    One backend-neutral lingua franca every consumer sees; every shape reduces to
+    (content|source, structure, provenance envelope, optional derivation rule).
+  includes:
+    - page identity (stable handle) vs placement (N paths/shards) vs equivalence (fingerprint)
+    - layered provenance envelope (page + span deltas)
+    - page-shape taxonomy incl. computational shapes
+  excludes:
+    - deriving identity from content (a fingerprint identifies a version, not a page)
+  use_cases:
+    - "shard-wiki UseCaseCatalog UC-34, UC-39, UC-44..UC-49, UC-55, UC-73, UC-83, UC-84"
+
+availability:
+  current_level: A2
+  target_level: A5
+  current_artifacts:
+    - "shard-wiki/src/shard_wiki/model/"
+    - "shard-wiki/src/shard_wiki/provenance/"
+  consumption_modes:
+    - source module
+
+relations:
+  supports:
+    - capability.wiki.adapter-contract
+    - capability.wiki.shard-orchestration
+
+evidence:
+  documentation:
+    - "shard-wiki/spec/CoreArchitectureBlueprint.md (Section 7)"
+    - "shard-wiki/spec/FederationRequirements.md (ADR-02, ADR-04)"
+  tests:
+    - "shard-wiki/tests/test_model.py"
+    - "shard-wiki/tests/test_provenance.py"
+
+consumer_guidance:
+  recommended_for:
+    - a portable, provenance-carrying representation of wiki pages across backends
+  not_recommended_for:
+    - cases needing a single canonical path per page (use identity, not path)
+  known_limitations:
+    - non-prose shapes specified ahead of implementation
+---
+
+# Backend-Neutral Wiki Page Model
+
+The top narrow waist: a Markdown-first model that stretches to typed records, typed-graph
+statements, inline-embedded objects, non-Markdown assets, and computational shapes. Identity
+is a stable handle; placement and equivalence are separate mechanisms; provenance is layered
+(effective = page envelope + span delta).
+
+## Assessment notes
+
+### Discovery
+Specified in CoreArchitectureBlueprint Section 7 and FederationRequirements ADR-02/04.
+
+### Availability
+`model/` + `provenance/` ship the prose path and the layered envelope today.

registry/capabilities/capability.wiki.shard-orchestration.md

@@ -0,0 +1,114 @@
+---
+id: capability.wiki.shard-orchestration
+name: Wiki Shard Orchestration
+summary: Present a union of pages across heterogeneous wiki-shaped shards while preserving each shard's provenance, capabilities, and history.
+owner: shard-wiki
+status: draft
+domain: helix_forge
+tags: [wiki, federation, orchestration, union, shard-wiki]
+
+maturity:
+  discovery:
+    current: D5
+    target: D6
+    confidence: high
+    rationale: >
+      Grounded in 84 documented use cases and a twice-reviewed whole-system
+      architecture (CoreArchitectureBlueprint) derived from ~23 prior-art systems.
+  availability:
+    current: A2
+    target: A5
+    confidence: medium
+    rationale: >
+      InformationSpace orchestrator (attach -> resolve -> read, chorus on
+      ambiguity) works as a Python source module; network API and incremental
+      union are planned.
+
+external_evidence:
+  completeness:
+    level: C2
+    name: Partial
+    confidence: medium
+    basis: scope_vs_intent_and_consumer_expectations
+    satisfied_expectations:
+      - attach folder shards and read a union page with layered provenance
+      - chorus presentation of equivalent-but-divergent pages (union without erasure)
+    broken_expectations:
+      - incremental union maintenance and equivalence index not yet built
+      - write-through federation transports not yet built
+    out_of_scope_expectations:
+      - hosting or replacing the underlying wiki engines
+  reliability:
+    level: R1
+    confidence: low
+    basis: consumer_quality_signals
+    known_reliability_risks:
+      - early implementation; 64 tests but no production exposure
+
+discovery:
+  intent: >
+    Let independently stored, differently implemented wikis behave as one
+    coherent, versionable, inspectable information space without homogenizing them.
+  includes:
+    - union resolution across shards (identity-keyed)
+    - chorus / designated-canonical presentation of equivalent pages
+    - lazy replication projection of remote content with freshness
+  excludes:
+    - implementing a backend wiki engine (see capability.wiki.engine-typed-extensions)
+    - silent remote mutation
+  assumptions:
+    - canonical truth lives in shards + a git coordination journal; the union is derived
+  use_cases:
+    - "shard-wiki UseCaseCatalog UC-01..UC-07, UC-26..UC-33 (information space, federation, coordination)"
+
+availability:
+  current_level: A2
+  target_level: A5
+  current_artifacts:
+    - "shard-wiki/src/shard_wiki/union/"
+    - "shard-wiki/src/shard_wiki/space.py"
+  target_artifacts:
+    - orchestrator network API
+  consumption_modes:
+    - source module
+
+relations:
+  depends_on:
+    - capability.wiki.adapter-contract
+    - capability.wiki.page-model
+    - capability.wiki.coordination-journal
+  supports:
+    - capability.wiki.federation-models
+
+evidence:
+  documentation:
+    - "shard-wiki/spec/CoreArchitectureBlueprint.md"
+    - "shard-wiki/spec/FederationArchitecture.md"
+  tests:
+    - "shard-wiki/tests/test_union.py"
+    - "shard-wiki/tests/test_integration.py"
+
+consumer_guidance:
+  recommended_for:
+    - composing multiple Markdown/wiki stores into one provenance-preserving view
+  not_recommended_for:
+    - replacing a single wiki engine
+  known_limitations:
+    - resolution is recompute-on-read until the incremental tier lands
+---
+
+# Wiki Shard Orchestration
+
+shard-wiki's core capability: orchestrate wiki-shaped content across heterogeneous *shards*
+as a union of pages, preserving provenance, capabilities, and history per shard. Canonical
+truth stays at the edges (shards + the git coordination journal); the union is a derived,
+recomputable view (orchestrator, not engine).
+
+## Assessment notes
+
+### Discovery
+Grounded by `UseCaseCatalog.md` (84 UCs) and the hardened `CoreArchitectureBlueprint.md`.
+
+### Availability
+`InformationSpace` provides attach/resolve/read today (source module); a network API is the
+target availability step.

registry/indexes/capabilities.yaml

@@ -0,0 +1,145 @@
+version: 1
+updated: '2026-06-16'
+domain: helix_forge
+capabilities:
+- id: capability.wiki.shard-orchestration
+  name: Wiki Shard Orchestration
+  summary: Present a union of pages across heterogeneous wiki-shaped shards while
+    preserving each shard's provenance, capabilities, and history.
+  vector: D5 / A2 / C2 / R1
+  domain: helix_forge
+  status: draft
+  owner: shard-wiki
+  path: registry/capabilities/capability.wiki.shard-orchestration.md
+  tags:
+  - wiki
+  - federation
+  - orchestration
+  - union
+  - shard-wiki
+  consumption_modes:
+  - source module
+- id: capability.wiki.adapter-contract
+  name: Capability-Aware Shard Adapter Contract
+  summary: A versioned backend interface where each binding declares a verified capability
+    profile, so federation ops degrade by capability.
+  vector: D5 / A2 / C2 / R1
+  domain: helix_forge
+  status: draft
+  owner: shard-wiki
+  path: registry/capabilities/capability.wiki.adapter-contract.md
+  tags:
+  - wiki
+  - adapter
+  - capability
+  - contract
+  - conformance
+  - shard-wiki
+  consumption_modes:
+  - source module
+- id: capability.wiki.page-model
+  name: Backend-Neutral Wiki Page Model
+  summary: A Markdown-first but stretchable page model with stable identity separate
+    from placement and layered provenance.
+  vector: D5 / A2 / C2 / R1
+  domain: helix_forge
+  status: draft
+  owner: shard-wiki
+  path: registry/capabilities/capability.wiki.page-model.md
+  tags:
+  - wiki
+  - page-model
+  - identity
+  - provenance
+  - markdown
+  - shard-wiki
+  consumption_modes:
+  - source module
+- id: capability.wiki.coordination-journal
+  name: Event-Sourced Coordination Journal
+  summary: An append-only, totally-ordered-per-space decision log whose current state
+    is a derived fold; git-addressable history.
+  vector: D5 / A2 / C2 / R1
+  domain: helix_forge
+  status: draft
+  owner: shard-wiki
+  path: registry/capabilities/capability.wiki.coordination-journal.md
+  tags:
+  - wiki
+  - event-sourcing
+  - coordination
+  - git
+  - journal
+  - shard-wiki
+  consumption_modes:
+  - source module
+- id: capability.wiki.overlay
+  name: Overlay-Before-Mutation Write Path
+  summary: Non-destructive edits (draft -> patch -> apply-under-drift) that let read-only
+    or limited backends be edited safely without silent remote mutation.
+  vector: D5 / A2 / C2 / R1
+  domain: helix_forge
+  status: draft
+  owner: shard-wiki
+  path: registry/capabilities/capability.wiki.overlay.md
+  tags:
+  - wiki
+  - overlay
+  - patch
+  - write-path
+  - conflict
+  - shard-wiki
+  consumption_modes:
+  - source module
+- id: capability.wiki.federation-models
+  name: Selectable Federation-Model Taxonomy
+  summary: Federation as a plural, composable coordination axis (fork+journal, VCS-replication,
+    query-join, feed, activity-streams, engine-mirror) selected per space.
+  vector: D4 / A0 / C1 / R0
+  domain: helix_forge
+  status: draft
+  owner: shard-wiki
+  path: registry/capabilities/capability.wiki.federation-models.md
+  tags:
+  - wiki
+  - federation
+  - taxonomy
+  - composable
+  - shard-wiki
+  consumption_modes:
+  - informational
+- id: capability.wiki.engine-typed-extensions
+  name: Wiki Engine with Typed Extensions
+  summary: A small-core wiki engine realizing a typed-extension framework that addresses
+    all wiki use cases and lets each shard activate only the features it needs.
+  vector: D3 / A0 / C0 / R0
+  domain: helix_forge
+  status: draft
+  owner: shard-wiki
+  path: registry/capabilities/capability.wiki.engine-typed-extensions.md
+  tags:
+  - wiki
+  - engine
+  - typed-extensions
+  - feature-activation
+  - shard-wiki
+  consumption_modes:
+  - informational
+- id: capability.wiki.derived-views
+  name: Wiki Derived Views
+  summary: Recomputable views over a wiki union — BackLinks, RecentChanges, AllPages,
+    SiteMap, and (delegate-or-derive) Search — carrying provenance.
+  vector: D3 / A0 / C0 / R0
+  domain: helix_forge
+  status: draft
+  owner: shard-wiki
+  path: registry/capabilities/capability.wiki.derived-views.md
+  tags:
+  - wiki
+  - derived-views
+  - backlinks
+  - recentchanges
+  - search
+  - shard-wiki
+  consumption_modes:
+  - informational

research/260614-computational-page-model-synthesis/README.md

@@ -0,0 +1,38 @@
+# 260614 — The computational page model (SHARD-WP-0004 synthesis)
+
+Date: 2026-06-15 · Source: **SHARD-WP-0004** post-batch synthesis (T1–T8)
+
+## What this is
+
+The acceptance-criteria synthesis for SHARD-WP-0004 — *"the computational page model"* —
+reading the eight computational/interactive-knowledge dives across each other and distilling
+them into **one model**: **source is canonical; everything rendered/computed is a
+projection**, placed on **two axes** (projection-kind: replication vs derivation; liveness:
+live↔snapshot), with a recommendation on an executable-content capability.
+
+## The answer to the carried question
+
+*Can a shard-wiki page be a live computational artifact?* **Yes — as a page-model +
+projection concern, not as an execution platform.** Every system externalizes to a canonical
+source and treats the live/computed form as derived; shard-wiki **recognizes** computational
+content, **attaches the source**, and **presents derivations as provenance- and
+liveness-marked projections**, with **execution as a gated capability (off by default,
+degrade to snapshot)**. No INTENT amendment required.
+
+## Key contributions
+
+- **One model:** `(source, derivation rule, projection with provenance + liveness)` covers
+  all four computational page shapes (one-source-many-projections UC-83; notebook UC-84;
+  program-as-page; live/temporal content).
+- **Two axes for T16:** replication vs **derivation-projection** (timing / multiplicity /
+  continuity facets) × the **live↔snapshot** axis (bounded at the irreducibly-live far end by
+  Strudel).
+- **One snapshot-provenance record** reused for notebook outputs, renders, recordings.
+- **Hard boundaries:** never host a kernel/runtime as store; **image-is-not-a-store**; never
+  present a derivation without output→source provenance.
+
+## Contents
+
+| Path | Role |
+|------|------|
+| `findings.md` | The source/derivation/projection model, the two axes, the four page shapes, provenance/reproducibility, the recommendation, the SHARD-WP-0002 fold-in, escalated open questions |

research/260614-computational-page-model-synthesis/findings.md

@@ -0,0 +1,178 @@
+# The computational page model — synthesis (SHARD-WP-0004)
+
+**Date:** 2026-06-15 · **Source:** SHARD-WP-0004 (post-batch synthesis, T1–T8) · **Kind:**
+synthesis (no new external research) reading the eight computational/interactive-knowledge
+dives *across* each other.
+
+## What this is
+
+The acceptance-criteria synthesis for SHARD-WP-0004. The batch asked one carried question:
+*can a shard-wiki page be a live computational artifact — a source woven/evaluated into
+rendered forms — and if so, how do projection, transclusion, provenance, and the adapter
+contract treat the source, the environment, and the computed output?* This memo answers it
+by distilling the eight dives into **one model**: the **source / derivation / projection**
+view of computational content, anchored on two axes, plus a recommendation on whether
+shard-wiki needs an executable-content capability.
+
+Dives consolidated: **T1** literate programming (WEB/weave/tangle), **T2** Mathematica,
+**T3** Jupyter, **T4** Processing/p5.js, **T5** Strudel, **T6** Squeak, **T7** Glamorous
+Toolkit, **T8** Pharo. Catalog yield: **UC-83** (literate one-source-many-projections),
+**UC-84** (notebook with computed-output provenance); the other six are **enrichment/boundary**
+dives (UC-54/55/47/48 + the projection model).
+
+## 1. The one finding: source is canonical, everything rendered is a projection
+
+Every system in the batch, however "live," **externalizes to a canonical artifact** and
+treats the rendered/computed form as **derived**:
+
+| System | Canonical (attach this) | Derived (a projection) |
+|--------|-------------------------|------------------------|
+| Literate (WEB) | the WEB/`.nw`/`.org` **source** | woven docs **and** tangled code |
+| Mathematica | the `.nb` (a Wolfram expression) | cached `Output` cells; CDF; `Dynamic` widgets |
+| Jupyter | `.ipynb` source (ideally paired text) | embedded outputs; nbconvert/nbviewer renders |
+| Processing | the **sketch source** | the view-time canvas render |
+| Strudel | the **pattern source** | the live audio performance / a recording |
+| GT / Lepiter | git-versionable **page/Tonel files** | moldable `gtView`s; live snippet results |
+| Squeak/Pharo | exported **files** (Tonel/git) | the live image / running objects |
+
+**This is the same principle shard-wiki already holds** (files-canonical, index/render
+derived — ikiwiki UC-79, Logseq UC-62, nbstripout). The computational batch did not break it;
+it **stress-tested it to the live extreme and it held**. *The image (Squeak/Pharo) is the
+only would-be exception, and it is a boundary, not a counterexample: an image is not a store.*
+
+## 2. Two axes the contract must add
+
+The batch refines the **projection model** (SHARD-WP-0002 T16) with two orthogonal axes:
+
+### 2.1 Projection kind: replication vs derivation
+- **Replication-projection** (the existing default): a lazy **cache/copy** of remote content
+  (Obsidian/Notion mirrors, UC-53/57).
+- **Derivation-projection** (new, from T1): a **transform/compile/weave/evaluate** of a
+  source into rendered forms — regenerable, may delegate to the source's tool, **degrades to
+  a captured snapshot** when the tool is absent. Covers weave/tangle, nbconvert, CDF, sketch
+  render, audio recording, `gtView`.
+
+Sub-facets of derivation (from T4): **materialization timing** = *ahead-of-time* (CDF,
+nbconvert, static HTML) vs *view-time* (Processing/Strudel); **multiplicity** = one output
+(UC-79) vs **N co-equal projections** (UC-83 weave+tangle; UC-47/48/54 moldable views).
+
+### 2.2 Liveness: the live↔snapshot axis (from T6, bounded by T5)
+Every derived view sits on a spectrum, and the more live the source, the more its static form
+is a clearly-marked degrading snapshot:
+
+```
+static source ── captured output ── live-over-files ── view-time one-shot ── continuous/
+(literate)       (notebook UC-84)    (GT/Lepiter)        (Processing)         interactive
+                                                                              ── irreducibly
+                                                                                 live/temporal
+                                                                                 (Strudel: source
+                                                                                  + recording only)
+```
+
+**Honesty rule (union-without-erasure):** a computed/live view must always declare *what it
+is* — "captured at run N, environment unguaranteed" (UC-84), "one performance, time T, source
+rev R" (UC-83/Strudel), "live render needs the runtime." Never present a snapshot as live or a
+static page as capturing a live artifact.
+
+## 3. The computational page-model shapes (T12)
+
+The batch adds these page shapes (beyond prose / typed records / query-defined / inline-
+embedded objects / typed-graph already catalogued):
+
+1. **One-source-many-projections** (UC-83) — a source whose presented forms are co-equal
+   derivations (docs + code), each with output→source provenance; **named-chunk transclusion**
+   assembles fragments by name at derivation time (UC-32/44).
+2. **Notebook** (UC-84) — **ordered/nestable cells** (Mathematica adds the outline tree)
+   where code cells own **embedded computed outputs** (the derived output is stored *inside*
+   the source) with **weak execution provenance**; outputs may be MIME blobs or **structured
+   re-evaluable values** (Mathematica) — a new point on the content-opacity spectrum.
+3. **Program-as-page** (Processing) — canonical content = **source text**, presentation = an
+   **executable render** with **no cached output**; non-Markdown executable content.
+4. **Live/temporal/generative content** (Strudel) — source canonical, render irreducibly
+   live; static = source + a marked recording.
+
+All four reduce to **(source, derivation rule, projection with provenance + liveness)** — one
+model, four positions.
+
+## 4. Provenance & reproducibility (the honest weakness)
+
+Computed output provenance is **real but fragile** everywhere: Jupyter/Mathematica
+`execution_count`/`In`-`Out` can be **out-of-order**; **environment/versions/data are not
+captured**; Strudel/Processing may be **non-deterministic**. Implication for the contract:
+treat a computed output as a **snapshot with declared, incomplete provenance** (run id, source
+rev, timestamp; environment "unguaranteed"), reusing **one snapshot-provenance machinery**
+across notebooks, recordings, and renders (UC-84 is the template). This is consistent with
+shard-wiki's existing "surface freshness/completeness, never imply more than you have"
+(Oddmuse partial-history UC-82).
+
+## 5. The recommendation
+
+**Does shard-wiki need an executable/computational content capability? — Yes, but only as
+recognition + projection + capability-gating, never as an execution engine.**
+
+1. **Adopt the source/derivation/projection model** (no execution required). shard-wiki
+   **recognizes** computational content types (literate source, notebook, sketch, pattern),
+   **attaches the canonical source**, and **presents derived forms as projections with
+   provenance + liveness markers**. This alone delivers UC-83/UC-84 and the enrichment of
+   UC-54/55 — and needs **no kernel, no sandbox, no runtime**.
+2. **Make execution a capability, off by default.** "Drive a derivation" (run tangle/weave,
+   re-execute a notebook, render a sketch, evaluate a pattern in the viewer) is a **gated
+   capability** with a **trust/sandbox** sub-concern (T11). Absent it, **degrade to the
+   captured snapshot / static render / recording** — the graceful-degradation rule, which the
+   batch shows always has an honest fallback (source is tiny and diffable everywhere).
+3. **One projection model, two axes** (T16): projection-kind (replication vs derivation; with
+   timing + multiplicity facets) × liveness (live↔snapshot). The **moldable view registry**
+   (T7) is the unifying structure — an open, type-keyed set of co-equal projections, none
+   canonical-by-fact (display-canonical is policy).
+4. **One snapshot-provenance record** reused for notebook outputs, renders, and recordings
+   (run id, source rev, timestamp, environment "unguaranteed").
+5. **Hard boundaries** (design-bugs if violated): never host a kernel/runtime as the store;
+   **image-is-not-a-store** (attach exported files); never present a derivation without
+   output→source provenance; never imply a static view captures a live artifact.
+
+**Net:** computational content is **in scope as a page-model + projection concern**, **out of
+scope as an execution platform** — exactly the mechanism-over-policy, capability-aware,
+degradable posture INTENT already mandates. No INTENT amendment is required; this extends the
+page model and projection model within existing constraints.
+
+## 6. Fold into SHARD-WP-0002
+
+- **T12 (page model):** add the four computational shapes (§3); allow nestable cells and
+  structured re-evaluable outputs; "derived output may live inside the source" (notebook).
+- **T16 (projection):** the **two-axis model** (§2) + the **moldable view registry** (§3/T7);
+  materialization-timing, multiplicity, continuity, and the live↔snapshot far end as explicit
+  projection metadata.
+- **T11 (capabilities):** "derive/execute/render/evaluate" as gated capabilities with trust/
+  sandbox; default off → snapshot.
+- **T15 (fidelity):** non-Markdown executable/computed content; lossy renders; the
+  structured-re-evaluable-value point on the content-opacity spectrum.
+- **T13 (history):** paired-text (Jupytext) / cell-aware (nbdime) strategies for embedded-
+  output documents; outputs-as-derived (nbstripout ethos).
+- **T14 (binding):** **image-is-not-a-store** boundary (export→files only).
+
+## 7. Open questions (escalated)
+
+1. Is **liveness** (and "irreducibly live / no faithful static form") an explicit first-class
+   metadata flag on every projection, so the union renders the honest fallback automatically?
+   (T5/T6 far-end question.)
+2. Does shard-wiki **ever drive a derivation** (sandboxed), or strictly attach + present
+   snapshots? (Recurs UC-56/UC-83/UC-84/T4/T5 — a single capability/trust policy decision.)
+3. Is a computed output's **structured re-evaluable value** (Mathematica/Wolfram) modeled as a
+   typed value or stored opaquely with provenance? (UC-55 open-Q #10; UC-84 Q3.)
+4. Should **UC-83** and **UC-84** eventually merge as two positions of one "source +
+   derivations" shape, or stay distinct? (Kept distinct: UC-84's defining trait is *output
+   embedded in source with weak provenance*; UC-83's is *N co-equal external derivations*.)
+
+## 8. Sources
+
+The eight SHARD-WP-0004 dives: `research/260614-{literate-programming,mathematica,jupyter,
+processing,strudel,squeak-pharo,glamorous-toolkit}-deep-dive/`. Prior projection/structure
+anchors: `research/260614-{ikiwiki,logseq,zigzag}-deep-dive/`,
+`research/260614-shard-spectrum-synthesis/`.
+
+## 9. Traceability
+
+No new UC (consolidation). Consolidates **UC-83, UC-84** and enrichments to **UC-32, UC-44,
+UC-47, UC-48, UC-54, UC-55, UC-79, UC-37, UC-35**. Feeds **SHARD-WP-0002 T11/T12/T13/T14/T15/
+T16** (see §6). Recommendation: computational content is **in scope as page-model + projection
+mechanism, out of scope as an execution platform**; no INTENT amendment required.

research/README.md

@@ -43,4 +43,5 @@ when multiple files or sources are involved. Findings here inform `spec/` and
 | 2026-06-14 | `260614-mathematica-deep-dive/` | Mathematica Notebooks — the original computational notebook (`.nb` = a Wolfram expression); nestable cell groups, structured re-evaluable outputs, `Manipulate` live widgets, CDF; confirms UC-84 notebook shape is a genus; SHARD-WP-0004 T2; enrichment-only (reinforces UC-84; UC-54/55) |
 | 2026-06-14 | `260614-squeak-pharo-deep-dive/` | Squeak & Pharo (image-based Smalltalk) — the live-object image (purest "live" end); image-is-not-a-store boundary (export→files only); Pharo Tonel/Iceberg externalizes code to git text; names the live↔snapshot projection axis; SHARD-WP-0004 **T6 + T8** (merged); boundary/enrichment-only, no new UC |
 | 2026-06-14 | `260614-processing-deep-dive/` | Processing / p5.js — program-as-page rendered live at view time (no cached output); adds materialization-timing + continuity facets to projection; execute-in-viewer = capability+trust; SHARD-WP-0004 T4; enrichment-only (UC-54/55) |
-| 2026-06-14 | `260614-strudel-deep-dive/` | Strudel.cc (TidalCycles JS) live-coding REPL — code as live time-based audio performance; the far live end (no faithful static form; static = source + marked recording); honesty test for graceful degradation; SHARD-WP-0004 T5; enrichment-only (UC-54/55) |
+| 2026-06-14 | `260614-strudel-deep-dive/` | Strudel.cc (TidalCycles JS) live-coding REPL — code as live time-based audio performance; the far live end (no faithful static form; static = source + marked recording); honesty test for graceful degradation; SHARD-WP-0004 T5; enrichment-only (UC-54/55) |
+| 2026-06-15 | `260614-computational-page-model-synthesis/` | **SHARD-WP-0004 synthesis** — *the computational page model*: source canonical / everything rendered is a projection; two axes (replication↔derivation, live↔snapshot); four computational page shapes; recommendation — executable content in scope as page-model+projection, out of scope as an execution platform (no INTENT amendment); feeds SHARD-WP-0002 T11–T16 |

spec/CoreArchitectureBlueprint.md

@@ -0,0 +1,976 @@
+# CoreArchitectureBlueprint — shard-wiki
+
+Status: **draft for review** · Date: 2026-06-15 · Owner: tegwick
+
+The whole-system architecture for shard-wiki, synthesised from `INTENT.md`, the 84-entry
+`UseCaseCatalog.md`, and the full research arc (`research/260608-*`, `research/260613-*`,
+`research/260614-*` — ~23 wiki/knowledge systems plus two cross-dive syntheses). This is the
+**core** blueprint: it defines the layers, the abstractions, and the load-bearing decisions
+that everything else implements.
+
+Scope relationship to the other specs:
+
+- **`ArchitectureBlueprint.md`** (existing) is the **authorization & history sub-blueprint**
+  (the L0–L4 ladder). This document references it as the design of the cross-cutting
+  authorization layer (§9) and does not restate it.
+- **`SHARD-WP-0002`** is the workplan that turns §6–§8 into
+  `spec/FederationArchitecture.md` + the adapter-contract section of
+  `spec/TechnicalSpecificationDocument.md`.
+- **`UseCaseCatalog.md`** is the demand this architecture must satisfy; UC references below
+  are load tests, not decoration.
+- **`WikiEngineCoreArchitecture.md`** designs shard-wiki's native, headless, API-first wiki
+  engine as a **canonical-mode shard backend** (one shard behind §6/§A — federation, union, and
+  projection stay here in the orchestrator, not in the engine). Added per the 2026-06-15 INTENT
+  amendment (decision `84ffdb48`, SHARD-WP-0013).
+
+---
+
+## 1. The thesis: *canonical vs derived* (three states)
+
+Everything in shard-wiki follows from one organising decision — that state comes in exactly
+**three kinds**, and only one of them is disposable:
+
+> **1. Sharded-canonical** — content owned by each shard (shard sovereignty).
+> **2. Coordination-canonical** — durable state *born inside shard-wiki* that encodes human
+> or cross-shard decisions and exists nowhere else: overlays (the local truth against a
+> read-only shard), curator equivalence bindings, alias tables, merge/reconciliation
+> decisions. It is recorded as an **append-only decision log in the Git coordination
+> journal** (event-sourced, §8.1); the *queryable current form* of that state (the effective
+> alias table, the equivalence set) is a **derived fold** of the log — i.e. tier 3, not tier 2.
+> What is canonical is the **log of decisions**, not any mutable snapshot of them.
+> **3. Derived-disposable** — everything shard-wiki *computes* from (1)+(2): the union graph,
+> equivalence index, query indexes, projections, views. It can be deleted and recomputed.
+>
+> **Canonical = sharded ∪ coordination. Derived = a pure function of canonical:**
+> `derived = f(sharded, coordination)`.
+
+This is the architectural form of "orchestrator, not engine." shard-wiki never *becomes* the
+source of truth; it composes sources and records the decisions it makes about them. The
+research earned the *files-canonical* half empirically — every serious system externalises its
+durable truth to files+VCS and treats the rest as derived: Logseq (DataScript index over plain
+files), ikiwiki (static HTML compiled from a git repo), Glamorous Toolkit / Lepiter (live
+views over git-versioned JSON), Pharo (Tonel/Iceberg code as git text), Jupyter teams
+(nbstripout — outputs are derived noise). The one tradition that refuses this — the Smalltalk
+**image** — is exactly the one we record as a *boundary, not a backend*
+(`research/260614-squeak-pharo-deep-dive`).
+
+The earlier draft of this blueprint used a two-bucket framing ("canonical at the edges,
+derived in the middle"). That was wrong by omission: it had no home for **coordination-
+canonical** state, and so contradicted itself by listing curator bindings and alias tables as
+"derived/rebuildable" when a human binding manifestly cannot be rebuilt. The three-state model
+fixes that crack (review finding A-1) and makes `derived = f(canonical)` *literally* true.
+
+Three consequences fall straight out, and they are the spine of the rest of this document:
+
+1. **Graceful degradation is free.** If the derived tier is always recomputable, a backend
+   that can only be read is still a first-class participant — you just derive less from it.
+2. **Provenance is tractable.** Because shard-wiki never claims to *be* the source, every
+   derived artifact can always point back to the canonical input it came from (union without
+   erasure is a structural property, not a feature bolted on).
+3. **The derived tier is a pure function of canonical state.** `derived = f(sharded,
+   coordination)`. Bugs in the derived tier are recoverable by recompute; only the two
+   canonical tiers must be durably protected — sharded by each shard, coordination by the
+   Git journal (history). *Recomputability is a correctness property of the derived tier, not
+   a promise that a from-scratch rebuild is operationally cheap — see §8.4 and the
+   operational-envelope axis.*
+
+### The dual narrow waist
+
+Heterogeneity is mediated at exactly two interfaces, and nowhere else:
+
+- **Bottom waist — the Shard Adapter Contract (§6).** Every backend, however weird, enters
+  through one versioned, capability-described interface.
+- **Top waist — the Wiki Page Model (§7).** Every consumer, however demanding, sees one
+  backend-neutral, Markdown-first-but-stretchable page model.
+
+Between the waists, core logic is written **once** against capabilities and the page model —
+never against a specific backend. Adding TiddlyWiki or Notion or a git forge is writing an
+adapter and declaring a capability profile, not editing core algorithms.
+
+---
+
+## 2. Architectural invariants
+
+These are non-negotiable. Violating one is a design bug, not a tradeoff. They are INTENT's
+principles fused with the research through-lines.
+
+| # | Invariant | Source |
+|---|-----------|--------|
+| I-1 | **Orchestrator, not engine.** Core composes shards; it never replaces or homogenises them. | INTENT Stability Note |
+| I-2 | **Three states; derived = f(canonical).** State is sharded-canonical, coordination-canonical (journal), or derived-disposable. The derived tier (union/index/projection) is a pure, recomputable function of the two canonical tiers; only canonical state is durably protected. | §1; Logseq/ikiwiki/GT through-line |
+| I-3 | **Capability-awareness is data.** A binding's abilities are a *profile* (positions on spectra), read by generic core logic — not per-backend branches. | synthesis v3 §2; INTENT capability-aware adapters |
+| I-4 | **Union without erasure.** Every page/revision/projection/overlay/view carries its provenance, freshness, liveness, and divergence. | INTENT; provenance-granularity spectrum (Wikibase) |
+| I-5 | **Overlay before mutation.** Writes to anything below write-through land as drafts/patches/MRs first; no silent remote mutation. | INTENT |
+| I-6 | **Git-addressable coordination.** Every information space has a Git-backed journal even when its shards are not git-native. | INTENT |
+| I-7 | **Mechanism over policy.** Canonical-source, conflict, editorial, sync cadence are configurable presets, never hard-coded. | INTENT |
+| I-8 | **Graceful degradation.** A limited backend is still usable as read-only / cache / projection / backup / patch target. | INTENT |
+| I-9 | **Identity ≠ placement.** A page is an entity that may occupy N locations; address by identity, not by path. | Trilium note/branch; ZigZag |
+| I-10 | **History is the floor.** Every write is a recoverable commit; recoverability, not gatekeeping, is the baseline protection. | ArchitectureBlueprint §2 |
+| I-11 | **Authorization in core, authentication delegated.** Core decides who-may; an external provider says who-is. | INTENT; ArchitectureBlueprint |
+| I-12 | **Not a file-sync daemon; not an execution platform.** Sync is wiki-page-semantic; computation is recognised+projected, not hosted. | INTENT; computational-page-model synthesis |
+| I-13 | **Tenant-partitioned derived state.** Derived state is partitioned by tenant/root entity; no derived artifact spans tenants except via explicit, authorised cross-root federation. | §9.1; review B-3 |
+
+---
+
+## 3. The layered architecture
+
+```
+        ┌───────────────────────────────────────────────────────────────┐
+        │  L6  Consumers — Orchestrator API · CLI/agents · Web/Obsidian   │
+        ├───────────────────────────────────────────────────────────────┤
+ X-cut  │  L5  Authorization (PEP/PDP, identity-provider iface) →         │ X-cut
+ Prove- │      see ArchitectureBlueprint.md (L0–L4 ladder)                │ Capa-
+ nance  ├───────────────────────────────────────────────────────────────┤ bility
+  ▲     │  L4  Union & Projection  (DERIVED · rebuild=fallback)           │   ▲
+  │     │      identity resolution · equivalence/chorus · union graph ·   │   │
+  │     │      replication+derivation projections · moldable view registry│   │
+  │     │      · derived query index                                      │   │
+  │     ├───────────────────────────────────────────────────────────────┤   │
+  │     │  L3  Coordination  (Git journal · overlay/patch engine ·        │   │
+  │     │      federation-model strategies · reconciliation)              │   │
+  │     ├───────────────────────────────────────────────────────────────┤   │
+  │     │  L2  Wiki Page Model  ── TOP WAIST ──                           │   │
+  │     │      backend-neutral pages · identity≠placement · span address ·│   │
+  │     │      provenance envelope · the page shapes                      │   │
+  │     ├───────────────────────────────────────────────────────────────┤   │
+  │     │  L1  Shard Adapter Contract  ── BOTTOM WAIST ──                 │   │
+  │     │      versioned iface · capability profile (orthogonal) ·        │   │
+  │     │      attachment-mode binding · operation verbs                  │   │
+  └──── ├───────────────────────────────────────────────────────────────┤ ──┘
+        │  L0  Backends (not ours): git repos, wiki/ subdirs, Gitea/      │
+        │      GitLab/GitHub wikis, folders, Obsidian, WebDAV, Notion,    │
+        │      Coulomb spaces, notebooks, …                               │
+        └───────────────────────────────────────────────────────────────┘
+```
+
+**Provenance** and **Capability** are drawn as vertical rails because they are not layers —
+they are present at every layer. A page object at L2 carries provenance; a projection at L4
+carries provenance; an authz decision at L5 records the context under which content was read.
+Likewise a capability profile declared at L1 is consulted at L3 (can we write-through?), L4
+(can we delegate a query?), and L5 (can this principal even reach the op?).
+
+The dependency rule is strict and downward, and it tracks the **three states (§1)**, not the
+layer numbers: **the derived-disposable tier (the whole of L4) may be deleted and recomputed
+from canonical state (sharded content at L1 + coordination-canonical state in the L3 journal).**
+Nothing canonical may depend on derived state. Note the journal at L3 is *canonical* (it holds
+overlays, bindings, aliases, merges); only L4 is disposable.
+
+---
+
+## 4. Core abstractions (the vocabulary code must use)
+
+Straight from INTENT, sharpened by research. New code maps onto these; it does not invent
+parallel terms.
+
+- **Shard** — an independently meaningful page store attached to a root entity, with
+  *sovereignty*: its own backend, capability profile, history, identity model, limits.
+- **Root entity / information space** — the joined space shards attach to; the unit of
+  Git coordination and of multi-tenancy (a tenant maps to a root entity, ArchitectureBlueprint).
+- **Shard adapter contract** — the versioned L1 interface; the bottom waist.
+- **Capability profile** — a shard binding's position on each of the 15 spectra (§6) plus its
+  supported verbs. *The* data structure that drives degradation.
+- **Wiki page model** — the L2 backend-neutral page; the top waist.
+- **Page identity vs placement vs equivalence** — a page is an entity with a *stable handle*
+  (identity); it may have N placements (paths/shards); **addressing and transclusion key on
+  identity, but equivalence keys on content fingerprint *across* identities** (§7.2, I-9). The
+  three are distinct mechanisms — never conflate identity with a fingerprint.
+- **Provenance envelope** — the metadata each artifact carries (source shard, freshness,
+  liveness, authz context, overlay status, divergence, lineage), stored **layered**: a
+  page-level envelope + span-level *deltas*, so per-span cost is near-zero when uniform (§7.3).
+- **Coordination journal** — the L3 Git-backed, **append-only decision log** for a space: the
+  durable home of all **coordination-canonical** state (§1, §8.1) as *events* (overlay-created,
+  binding-made, alias-set, merge-decided), plus the content change-flow record. It is event-
+  sourced — committed, never overwritten; the queryable current coordination state is a derived
+  fold of it (§8.1).
+- **Overlay** — a non-destructive local edit against a remote/read-only/limited shard,
+  representable as draft/patch/commit/MR before destructive apply. Coordination-canonical: an
+  unapplied overlay is the local truth and lives in the journal.
+- **Projection** — a derived view of shard content. The default is a **plain lazy
+  replication-projection** (a freshness-stamped cache); only *source* content needing
+  transform/evaluate uses the **derivation-projection** extension point with its two-axis
+  typing (kind × liveness) and the moldable view registry (§8.4–§8.5).
+- **Federation model** — the selected coordination strategy for a space (§ taxonomy, T17).
+- **Shard mode** — read-only · write-through · mirrored · projected · cached · canonical
+  (a *policy* selection constrained by the capability profile).
+
+---
+
+## 5. Why "layered" and not "pipeline" or "plugin-bus"
+
+Two rejected alternatives, recorded so the choice is legible:
+
+- **A sync pipeline** (source → transform → sink) was rejected: it implies a privileged
+  direction and a canonical sink, which violates shard sovereignty (I-1) and union-without-
+  erasure (I-4). shard-wiki is a *star* (many shards ↔ one space), not a pipe.
+- **A flat plugin bus** (every backend a peer plugin emitting events) was rejected as the
+  *top-level* shape: it has no narrow waist, so heterogeneity leaks into every consumer.
+  We keep the plugin idea but confine it to L1 (adapters) and L3 (federation strategies),
+  behind the waists.
+
+The layered-with-rails shape is what makes I-2/I-3/I-4 hold simultaneously.
+
+---
+
+## 6. Bottom waist — the Shard Adapter Contract (L1)
+
+The single most important design decision in the project: **the adapter contract models
+positions on capability spectra, not a flat checklist of boolean verbs.** A backend is not
+"can/can't merge"; it sits *somewhere* on the merge spectrum, and federation operations
+degrade by position. This is the lesson of putting ~23 systems in one matrix
+(`research/260614-shard-spectrum-synthesis`, v3).
+
+### 6.1 The fifteen capability spectra
+
+Each binding declares a position on each axis. Core algorithms read these positions; there is
+no per-backend code in core (I-3).
+
+1. **Addressing granularity** — none → path → page-level store-id → in-file span → in-file
+   block id (Logseq `id::`) → store-UUID → portable tumbler (Xanadu, the unreached ideal)
+2. **Content identity** — none → path/title → fingerprint → span-set
+3. **Identity vs placement** — path=identity → identity separated from placement (Trilium
+   note/branch = a DAG)
+4. **Structure** — flat MD → frontmatter/`key::` → `%META%` → typed objects → DB schema+
+   relations → object-graph/ontology → computed (inherited+templated) → typed-graph statements
+5. **History** — none → internal-only / CRDT-log → open-file → git-native
+6. **Merge model** — none → git/text → conflict-notes/keep-both → native-CRDT → coexist-with-rank
+7. **Native query** — none → text → build-your-own derived index → datalog/graph → DB query → SPARQL
+8. **Translation** — native → lossless → lossy-with-fidelity-report (incl. HTML)
+9. **Attachment mode** — file-store (native | interchange-mirror) → git-IS-store → in-engine-host
+   → local-REST → external-API → direct-DB → CRDT-replica → P2P/no-central-endpoint
+10. **Operational envelope** — local/unbounded → realtime CRDT/WebSocket → rate-limited/
+    eventually-consistent/paginated
+11. **Access grant** — open → token → OAuth scoped+revocable → P2P key/invite → enterprise ACL
+12. **Content opacity** — plaintext → structured re-evaluable value → encrypted whole-shard →
+    per-item → proprietary-lossy-exportable
+13. **Write granularity** — whole-file (TiddlyWiki) → per-page → section/anchor → per-block → story-item
+14. **Provenance granularity** — per-shard → per-page → per-edit → per-statement/value (Wikibase rank+refs)
+15. **Computational / liveness** — static source → captured-output snapshot → live-over-files →
+    view-time render → irreducibly-live/temporal
+
+### 6.2 Operation verbs
+
+`read, write, diff, merge, lock, version, publish, notify, transclude-source,
+translate-syntax, structured-payload, derive-projection, execute/evaluate`. The last two are
+**gated, off by default** (§8, computational content). Verb support is part of the profile and
+must reconcile with the federation-ops capability matrix (SHARD-WP-0002 T10).
+
+### 6.3 Attachment-mode taxonomy (axis 9, expanded)
+
+A backend may offer **several** modes; attach mode is a **per-binding, capability-gated
+choice**, with one declared authoritative. Modes: file-store (native vault/folder *or* an
+interchange/sync mirror), **git-IS-store** (the home case — forge wikis & ikiwiki: git is the
+store *and* the journal at once, resolving the engine-mirror write-race), in-engine hosted
+adapter (XWiki component, Obsidian/Logseq/Roam plugin, Trilium script), local-REST (Joplin
+Data API, Trilium ETAPI), external-API-only (Notion), direct-DB (MojoMojo schema→model),
+CRDT-replica (Anytype/AFFiNE/AppFlowy), P2P/no-central-endpoint. **Boundary:** a monolithic
+live-memory blob (Smalltalk image, a kernel) is **never** an attach target — it participates
+only via export→files (I-12).
+
+### 6.4 Contract rules
+
+- **Versioned interface** (Foswiki::Store + Foswiki::Meta is the proof that a stable
+  store-interface-with-swappable-backends works). Capability discovery is a static profile
+  with optional runtime negotiation.
+- **Backend-swap tolerance** — shard identity/provenance survives a substrate change
+  (RCS↔PlainFile, folder→Git, Logseq file→SQLite): bind to *capabilities*, not to "it's files."
+- **Absence is first-class** — the profile must express *can't* cleanly (Oddmuse floor), so
+  degradation paths are explicit, never guessed.
+
+### 6.5 Orthogonal core, implied positions, and the interaction subset
+
+Fifteen independent ordinal axes is *descriptively* right but would be *operationally* a mess
+if treated as fifteen free dimensions: the axes are **not orthogonal**, and a degradation
+function over all 15 jointly is the flat-checklist problem returning in higher dimensions
+(review D-1). Three rules tame it.
+
+**(a) A small orthogonal core; the rest are implied.** Most axes are *correlated* and collapse
+to a few independent choices. The **core axes** an adapter must independently declare:
+
+1. **Substrate** → drives attachment-mode, history, merge, and native-query positions together
+   (git-IS-store ⟹ history=git-native ⟹ merge=git/text ⟹ query=build-your-own-index;
+   relational-DB ⟹ direct-DB attach ⟹ DB-version-row history ⟹ DB query).
+2. **Write granularity** → drives addressing granularity and the overlay/patch shape.
+3. **Content opacity** → drives translation and (where encrypted) collapses native-query.
+4. **Operational envelope** → drives freshness mode (§8.8) and rebuild expectations (§8.7).
+5. **Access grant** → independent (authz, L5).
+6. **Computational/liveness** → independent (projection kind, §8.5).
+
+The remaining axes are **implied/derived** from these via published implication rules; an
+adapter *may* override an implied position, but the default is computed, not hand-set. This
+turns ~15 free dimensions into ~6 independent ones plus derivations — fewer things to get
+wrong, and impossible combinations become unrepresentable.
+
+**(b) Implication rules forbid impossible profiles.** E.g. `attachment=git-IS-store ⟹
+history≥git-native`; `opacity=encrypted-whole-shard ⟹ native-query=none ∧ translation≤opaque`;
+`merge=native-CRDT ⟹ history=CRDT-log ∧ envelope=realtime`. A profile that violates an
+implication is rejected at registration — capability-as-data (I-3) with integrity constraints.
+
+**(c) The degradation function reads a *named, small* interaction subset — not all pairs.**
+"No per-backend code" is only credible if we say *which* axis interactions the generic logic
+actually consults. They are:
+
+| Operation | Axes consulted (jointly) |
+|-----------|--------------------------|
+| **write / overlay-apply** | write-granularity × merge-model × history × access-grant |
+| **transclude / address a span** | addressing-granularity × write-granularity × identity-vs-placement |
+| **project / cache** | operational-envelope × computational-liveness × content-opacity |
+| **query** | native-query × content-opacity (encrypted ⇒ derive-index-or-none) |
+| **translate** | translation × content-opacity × structure |
+| **federate** | substrate × history × merge (per the §8.3 model) |
+
+Everything else is a single-axis check. This table *is* the degradation contract: it is small,
+enumerated, and testable — the proof obligation behind "core logic written once."
+
+### 6.6 Conformance — profiles are verified, never self-asserted
+
+Capability-as-data (I-3) and the entire degradation contract (§6.5) rest on one assumption:
+**the profile tells the truth.** If an adapter declares `merge=git/text` but corrupts merges,
+or claims `notify` and never emits, it silently poisons every degradation decision in core —
+the failure is invisible because core *believed the data* (review B-2). So the profile is not
+taken on trust:
+
+- **The contract ships a versioned conformance suite.** A published battery that, given a live
+  binding, **exercises each declared verb and each declared spectrum position and checks that
+  observed behaviour matches the claim** (a `write` round-trips; a `diff` is real; `notify`
+  actually fires; an "encrypted/opaque" shard genuinely refuses plaintext query; an
+  implication-rule position, §6.5(b), holds). The suite is versioned *with* the contract, so an
+  adapter proves conformance against a known contract version.
+- **Passing conformance is an admissibility precondition.** A binding that fails (declares a
+  capability it does not honour) is **rejected at registration**, not run in production with a
+  lying profile. Capability discovery (§6.4) therefore yields a *verified* profile.
+- **Self-reported, then verified.** Adapters still *declare* their profile (discovery stays
+  cheap); conformance *verifies* the declaration. The two together are what make I-3 and §6.5
+  sound rather than aspirational — degradation logic acts on verified data.
+- **Mismatch is data, not a crash.** A conformance gap is reported as a precise
+  capability-by-capability diff (what was claimed vs observed), so an adapter author fixes the
+  profile or the code; degraded-but-honest registration (drop the unsupported claim) is allowed.
+
+This is the same discipline a versioned store interface needs in general (the `Foswiki::Store`
+lineage that inspired the contract): a backend may only participate behind the interface if it
+*demonstrably* behaves as the interface says.
+
+---
+
+## 7. Top waist — the Wiki Page Model (L2)
+
+Backend-neutral, **Markdown-first but stretchable many ways at once**. The page model is the
+lingua franca every consumer sees; an adapter's job is to project its backend into this model
+(read) and accept overlays back (write), within its capabilities.
+
+### 7.1 Page shapes the model must carry
+
+- **Prose Markdown** — the baseline.
+- **Typed / computed records** — frontmatter/`%META%`/XObjects/Notion DB rows; **computed
+  metadata** (Trilium inherited+templated) represented as *effective-vs-own with per-attribute
+  provenance*.
+- **Typed-graph statements** — Wikibase claim + qualifiers + references + rank (structure
+  far-end).
+- **Inline-embedded objects** — Quip/Notion spreadsheets & live apps inside prose.
+- **Non-Markdown assets** — drawings, canvases, images: typed asset / opaque blob / pluggable
+  content-type registry, never silent-flattened.
+- **The four computational shapes** (§8): one-source-many-projections, notebook (embedded
+  computed output), program-as-page, live/temporal.
+
+All shapes reduce to a common skeleton: **`(content | source, structure, provenance envelope,
+[derivation rule])`**. The page model stores the richest faithful form as canonical and treats
+any Markdown rendering of a non-Markdown shape as a *lossy projection* (I-4 + fidelity report).
+
+### 7.2 Identity, placement, addressing — three distinct concepts
+
+The earlier draft used "identity" for two different things and (worse) suggested deriving page
+identity from a content fingerprint — which would make *editing a page change its identity* and
+break every reference to it (review bug B-1). They are pulled apart here:
+
+- **Page identity — a *stable handle*.** A shard-scoped, durable key that **survives edits**:
+  the backend's native page/note id where one exists (Roam/Notion/Trilium uid, a git path
+  treated as a name, a wiki page name), wrapped in a shard scope so it survives projection and
+  never collides across shards. Identity is *assigned/minted, not computed from content*.
+  References, placement, transclusion targets, and overlays all key on identity.
+- **Placement — *where* an identity sits.** One identity → N placements (paths/shards) = a DAG;
+  no single canonical path (I-9). Placement can change without changing identity.
+- **Content equivalence — *detecting sameness*, never identity.** A **content fingerprint** (or
+  span-set overlap) identifies a *version / a piece of content*, used to detect that two
+  *distinct identities* hold the same or derived content (the equivalence/chorus mechanism,
+  §8.4). A fingerprint is never a page's identity: same page, edited → new fingerprint, **same
+  identity**; two pages, identical content → same fingerprint, **different identities**.
+- **Span addressing** — a sub-page address within an identity: adopt native span IDs where
+  minted (Roam `:block/uid`, Logseq `id::`, Notion/CRDT UUID); else a *position* address
+  (path+range) or a *content-fingerprint* address for equivalence/transclusion. The Xanadu
+  tumbler is the portable ideal the scheme aims at without requiring.
+- **Provenance envelope** rides on pages and spans (see §7.3 for its layered, low-cost form).
+
+So the chain is: **identity (stable) → placements (N, mutable) → equivalence (cross-identity
+sameness, fingerprint-based)** — three concepts, three mechanisms, never conflated.
+
+### 7.3 Provenance is layered, not per-span-duplicated
+
+A provenance envelope on *every span* (source shard, freshness, liveness, overlay status,
+authz context, divergence, lineage) would, at block granularity, mean ~10k near-identical
+envelopes for a 10k-block page — provenance dwarfing content (review D-2). The fix is the exact
+pattern the page model already uses for Trilium's computed metadata: **effective-vs-own**.
+
+- **Page-level envelope** holds the values that are uniform across the page (almost always:
+  source shard, observed-at, liveness, authz context).
+- **Span-level deltas** record *only where a span differs* from its page envelope — a
+  transcluded span from another shard, an overlaid span, a span that diverges. A span with no
+  delta inherits the page envelope at zero storage cost.
+- **Effective provenance** for any span = page envelope ⊕ span delta, computed on read.
+
+Per-span cost is therefore **near-zero in the common (uniform) case** and pays only for genuine
+heterogeneity — the same "carry only the difference" principle, applied to shard-wiki's own
+metadata. Provenance remains complete (I-4); it is just not redundantly materialised.
+
+---
+
+## 8. Coordination, federation & projection
+
+### 8.1 Coordination journal (L3) — Git as the spine
+
+Every information space has a Git-backed coordination journal (I-6). It records cross-shard
+operations (fork, import, reconcile, overlay-apply, space-branch) and **is** the history floor
+(I-10). For git-IS-store shards the shard's own git log *is* this journal; for non-git shards
+the journal supplements (begins-now / mirrors-forward / snapshots-replica) or imports
+(backfill open file history). History portability is a spectrum, handled per profile (axis 5).
+
+**The journal is an append-only decision log; current coordination state is a derived fold
+(review B-3).** The first draft said coordination-canonical state "lives in the journal"
+without saying how Git — excellent for history, poor for mutable structured state — represents
+an alias table or an equivalence graph. Resolution: **event sourcing.** The journal stores
+*decisions as events* (`overlay-created`, `binding-made`, `alias-set`, `merge-decided`,
+`page-forked`), append-only and git-addressable (so history/patch/review/backup over
+coordination state come for free — I-6 is *strengthened*, not bypassed). The **queryable
+current state** (the effective alias table, the live equivalence set) is a **derived fold** of
+the log — tier-3 disposable, indexed like any other derived structure (§8.7), rebuilt by
+replaying the log. So "all equivalences touching X" is an index lookup, not an O(scan) of Git.
+This is the clean form of the §1 three-state model: **the log is canonical; its folded current
+state is derived.**
+
+**Concurrency: who may append (review B-1).** A multi-tenant L4 deployment runs several
+orchestrator instances, so "the journal is local Git, single writer" is not given. The model:
+
+- **One *append authority* per information space.** Appends to a space's log are serialized
+  through a single logical writer (a per-space lease/leader; instances without the lease forward
+  their append intents to it). This makes the log a **totally-ordered event sequence** per space
+  — the ordering authority §8.6 relies on — without a distributed transaction. Spaces are
+  independent, so this scales horizontally *across* spaces (the unit of partition is the space /
+  root entity, matching the tenant partition, I-13); it is a per-space serialization point, not
+  a global one.
+- **Git is the durable, addressable form; appends are commits** (or fast objects batched into
+  commits) under the lease — no concurrent-writer merge races because there is one writer at a
+  time per space.
+- **Read-your-writes** holds within a space because every reader resolves current state from
+  the same ordered log (or its fold); across spaces there is no shared state to be inconsistent.
+- **HA / failover:** the lease is time-bounded and re-grantable; a failed append-authority is
+  replaced and resumes from the log's head (the log is the recovery point). A partition that
+  splits the authority degrades that *space* to read-only until a single writer is re-elected —
+  it never forks the log (availability yields to log integrity; an explicit, stated trade).
+- **Open residual (→ §12, O-3-adjacent):** whether very high append rates need per-space log
+  *sharding* (sub-logs merged by a deterministic order) is an implementation spike, not an
+  architectural change.
+
+**History must stay recoverable *and* bounded (review C-3).** "Every write is a commit" + open
+L0 means an unbounded, bot-/vandalism-amplified journal that eventually degrades Git itself.
+Recoverability (I-10) is non-negotiable, so the answer is *compaction, not deletion*:
+
+- **Routine git maintenance** — background `gc`/repack, commit-graph, and (for very large
+  spaces) partial-clone / sparse strategies; operational, no semantic change.
+- **Squash-compaction of low-value churn (policy, §10)** — long runs of rapid same-author
+  edits or revert-pairs can be folded into checkpoint commits *while preserving the recoverable
+  endpoints*; what is squashed is configurable and always leaves the content recoverable (it
+  compacts the *path*, not the *reachable states*).
+- **Per-shard history offload** — a git-IS-store shard keeps its own history in its own repo;
+  the coordination journal references it rather than duplicating it (the journal records
+  *coordination* events, not a second copy of every shard commit).
+- **Anti-abuse hooks (policy)** — rate-limiting / quarantine for anonymous L0 writers feed the
+  authz/policy layer; they throttle *abuse*, never legitimate history. Recoverability is the
+  floor; bounding is how it survives at scale.
+
+### 8.2 Overlay / patch engine (L3)
+
+The default write path for anything below write-through capability (I-5): an edit becomes a
+draft → patch/commit → MR, applied destructively only on explicit intent and only where the
+profile + policy both permit. This is what lets a read-only or rate-limited or lossy backend
+still be *edited* safely.
+
+### 8.3 Federation is plural & composable (L3) — the model taxonomy
+
+Federation is not one mechanism. shard-wiki selects a **federation model per space and
+composes per shard** (mechanism over policy, I-7):
+
+| Model | Anchor | Coordination shape |
+|-------|--------|--------------------|
+| **Fork + journal** (default home case) | Federated Wiki | copy-with-provenance + per-page action journal (story = replay) |
+| **VCS-replication + ping** | ikiwiki | git clone/pull/push + change-ping |
+| **Query-time graph-join** | Wikibase SPARQL `SERVICE` | join remote graphs at query time, no copy |
+| **Feed aggregation** | RSS/Atom | inbound feed → pages |
+| **Activity streams** | ActivityPub | Create/Update events, notify or content-bearing |
+| **Engine-mirror** | Wiki.js DB↔Git | engine syncs its own store to a git mirror |
+
+### 8.4 Union & projection (L4) — the derived cache
+
+This whole layer is **derived-disposable**: recomputable from canonical state — sharded
+content + the **coordination-canonical** inputs in the journal (I-2). Crucially, the *automatic*
+equivalence results are derived, but the **human/curatorial inputs they consume — alias tables
+and curator equivalence bindings — are coordination-canonical (they live in the journal), not
+derived**; recompute reads them, never regenerates them. It comprises:
+
+- **Identity resolution & equivalence** — detect "same topic / derived content" path-
+  independently from *derived* signals (content fingerprint, span-set overlap) **plus** the
+  *coordination-canonical* inputs (alias table, curator binding); present as
+  **chorus-of-voices** or designated-canonical (a *policy* preset). (Scaling: §8.7.)
+- **Union graph** — the navigable join of pages, links, and dimensions (namespace, genealogy,
+  version, shard, equivalence). A *derived lens over canonical files+journal, never a new
+  store* (the ZigZag boundary).
+- **Transclusion** — one **reference-not-copy** primitive unifying Xanadu transclusion, ZigZag
+  clone, Roam/Obsidian/Logseq embed, Notion synced block, Trilium note-cloning, and literate
+  named-chunk assembly, over the addressable union.
+- **Projection — trivial by default, extensible for the tail.** The 95% case (Markdown in a
+  shard) must cost nothing conceptually, so:
+  - **Default = plain lazy replication-projection** — a freshness-stamped cache of remote
+    content (§8.8). This is *the* projection for ordinary pages; it needs no taxonomy, no
+    liveness reasoning, no registry. Most shards never touch anything below.
+  - **Extension point — derivation-projection** — invoked *only* for content that is a
+    *source* needing transform/compile/weave/evaluate (computational/typed content, §8.5). It
+    adds the liveness axis (static → captured → live-over-files → view-time → irreducibly-live)
+    and facets (materialization timing, multiplicity, continuity); the irreducibly-live far end
+    has no faithful static form (source + a marked recording). A binding that never serves such
+    content never instantiates any of this.
+  - Both kinds stamp freshness + provenance; only derivation carries the liveness machinery.
+- **Moldable view registry — also an extension point, not a tax on every page.** Where a content
+  type offers multiple co-equal views (typed/computed/dimensional content), they are registered
+  as an **open, type-keyed set, none canonical-by-fact** (display-canonical is policy; GT prior
+  art, answers the "pluggable content-type registry" question). An ordinary Markdown page has
+  exactly one view and never consults the registry — the registry is queried only when a type
+  declares >1 view.
+- **Derived query index** — delegate to a shard's native query engine where present
+  (Roam/Logseq Datalog, Notion DB query, XWiki XWQL, Wikibase SPARQL); else build a derived
+  index over the projection (the Logseq DataScript-over-files pattern). The index is
+  disposable (I-2).
+
+### 8.5 Computational / executable content — the scope decision
+
+**In scope as a page-model + projection concern; out of scope as an execution platform.**
+shard-wiki *recognises* computational types, attaches the **canonical source**, and presents
+derived forms as **provenance- and liveness-marked projections**. Driving a derivation
+(tangle/weave, re-execute a notebook, render a sketch, evaluate a pattern) is a **gated
+capability, off by default, with a trust/sandbox concern, degrading to a captured snapshot**.
+One snapshot-provenance record (run id, source rev, timestamp, environment "unguaranteed")
+serves notebooks, renders, and recordings alike. **No INTENT amendment is required** — this
+lives inside the existing page model (L2) and projection model (L4).
+
+### 8.6 Consistency, concurrency & conflict model
+
+INTENT makes real-time cross-shard consistency a non-goal — but "no strong consistency" is not
+the same as "no defined consistency." This is the guarantee shard-wiki *does* offer, and the
+mechanism (not policy) that makes concurrent editing safe (review bug B-2).
+
+**The consistency guarantee — causal, anchored on the journal:**
+
+- **Read-your-writes for coordination-canonical state.** Once an overlay/binding/merge is
+  appended to the space's decision log, every reader of that space sees it — because the log is
+  a **single totally-ordered sequence per space** (one append authority, §8.1), and all readers
+  resolve current state from that one order. The guarantee holds across orchestrator instances,
+  not just within one process; it is cheap because ordering is per-space, never global.
+- **Causal consistency across the derived tier.** The union/index/projections reflect a causal
+  cut of `(sharded inputs seen so far, journal)`. Effects never appear before their causes; a
+  projection that has seen journal commit *C* has seen everything *C* depends on.
+- **Eventual convergence for sharded-canonical inputs.** Remote shard content is pulled
+  asynchronously (lazily or by notify/poll, §8.7); the union converges to each shard's latest
+  *as observed*, bounded by the shard's operational envelope. Freshness is always *shown*
+  (provenance envelope), never faked — a stale projection is labelled stale, not wrong.
+
+So: **strong + read-your-writes for what shard-wiki owns (the journal); causal for what it
+derives; eventual + freshness-labelled for what shards own.** No global clock, no distributed
+transaction, no two-phase commit across shards — none is needed, because shard-wiki coordinates
+rather than controls.
+
+**Conflict detection & representation is core mechanism; only resolution is policy (I-7).**
+The split the earlier draft elided:
+
+- **Detection (core).** Divergence is detected structurally: two identities resolve as
+  equivalent (§8.4) but their content fingerprints differ, or an overlay's base revision no
+  longer matches the shard's current revision. Detection is always on; it is never optional.
+- **Representation (core).** A detected conflict is **first-class data in the union**, not an
+  error: equivalent-but-divergent pages are presented as a **coexisting set** (the
+  chorus/keep-both representation), each fully attributed, with the divergence recorded in the
+  provenance envelope (union without erasure — a conflict is information, not a failure).
+- **Resolution (policy).** *Which* version wins, or whether they stay coexisting, is a
+  configurable preset (§10): chorus / designated-canonical / git-merge / vote-to-merge /
+  overlay-only. Core never hard-codes one.
+
+**Overlay-apply under source drift (the concurrent-write case).** An overlay carries the
+**base revision** of the shard content it was authored against. On apply, core compares base to
+the shard's current revision:
+
+- *unchanged* → apply (fast-forward), commit to journal, propagate if the profile permits;
+- *changed, non-overlapping* → three-way merge where the merge capability allows (axis 6),
+  else keep-both;
+- *changed, overlapping* → **refuse + re-present** as a conflict (above); never silently
+  clobber (I-5, no silent remote mutation). The unapplied overlay remains coordination-
+  canonical and valid against its base.
+
+**Ordering.** The journal commit is the ordering authority for coordination-canonical effects;
+a shard-native write is only *acknowledged* in the journal after the adapter confirms it, so a
+crash between journal-intent and shard-write is recoverable (the intent is replayable, the
+write is idempotent-keyed on identity+base-rev). Cross-shard operations are ordered by their
+journal commits, giving the causal cut above.
+
+**Residual open items** (tracked in *Known scaling risks & open problems*, §12, not pretended
+solved): the exact convergence bound for
+high-write CRDT shards under partition, and whether per-equivalence-set divergence needs a
+vector clock vs. a simple base-rev comparison, are deferred to implementation spikes.
+
+### 8.7 Scaling the union — incremental-first, rebuild as fallback
+
+The derived tier is *recomputable* (I-2) but recompute must never be the **operational**
+mechanism. A from-scratch rebuild reads every page of every shard — including rate-limited,
+paginated external APIs (Notion) and irreducibly-live sources — which can take hours to days
+and directly fights the operational-envelope axis (review C-2). So:
+
+**Incremental, change-driven maintenance is the primary mechanism.** Each shard's `notify`
+capability (or a poll/ETag fallback where it has none, §8.8) emits **change events**; an event
+drives a **delta update** to exactly the affected union nodes, equivalence candidates, indexes,
+and projections. The derived tier is a continuously-maintained materialised view, not a
+periodically-recomputed one. Steady-state cost is O(changes), not O(corpus).
+
+**Full rebuild is a rare, bounded fallback** — for cold start, schema/algorithm change, or
+suspected corruption — and it is **explicitly not required to be cheap**. It respects each
+shard's envelope (it may be slow, throttled, or resumable for a rate-limited shard) and runs
+*concurrently with serving the existing derived tier*; it swaps in atomically on completion.
+I-2 guarantees rebuild is *possible and correct*, not instant.
+
+**Equivalence detection is indexed, not pairwise (review C-1).** Naive fingerprint/span-set
+comparison across all pages of all shards is O(N²) and is forbidden. Instead:
+
+1. **Blocking / candidate generation** — cheap keys bucket pages that *could* be equivalent:
+   normalised title, normalised path tail, explicit alias-table entries (coordination-
+   canonical), and **MinHash/LSH bands over content shingles** for near-duplicate and
+   derived-content detection. Only within-bucket pairs are considered — turning O(N²) into
+   ≈O(N) candidates.
+2. **Verification** — candidate pairs are confirmed by full fingerprint / span-set overlap and
+   any curator binding. Confirmed equivalences become union edges.
+3. **Incremental maintenance — the delta is *not* additive (review B-4).** A changed page may
+   *leave* buckets as well as *enter* them, and leaving a bucket can **break an existing
+   equivalence edge** another page relied on. So a change is processed as: (i) recompute the
+   page's bucket membership; (ii) for buckets it **left**, re-verify the pairs that depended on
+   the shared bucket and **retract** edges no longer supported; (iii) for buckets it **entered**,
+   verify the new candidate pairs and **add** edges; (iv) **propagate** to the equivalence
+   neighbours of any retracted/added edge (equivalence is transitive-ish via chorus sets, so a
+   retraction can split a set). Maintenance is per-change and bounded by the page's
+   neighbourhood, but it covers retraction and propagation — not just additions.
+
+**The index is itself derived** (disposable, recomputable) and per-tenant-partitioned (§9).
+Its parameters (LSH band/row counts, shingle size, precision/recall) are tunable; the accepted
+**false-negative rate of blocking** is a known, tracked limitation (§12) — blocking trades a
+small miss rate for tractability, and curator bindings are the escape hatch for misses.
+
+**Verifying I-2 (`derived = f(canonical)`) — eventually, not on faith (review B-4).**
+Incremental maintenance can drift from a from-scratch fold over time (a missed retraction, a
+dropped event, a bug). I-2 is therefore an **eventually-verified** property, not a free one,
+and the architecture names the mechanism that verifies it:
+
+- **A digest of the derived tier.** Each partition's derived tier carries a rolling content
+  digest (a Merkle-style hash over union nodes/edges/index entries) maintained alongside the
+  incremental updates.
+- **A background consistency-checker** periodically recomputes the digest over a *sampled* (or,
+  on a slow cadence, full) fold of canonical state and compares. A mismatch localises the drift
+  to a partition/region and triggers a **scoped recompute** of just that region — cheap relative
+  to a global rebuild, and self-healing.
+- **So I-2 holds *eventually and verifiably*:** the incremental engine is the fast path, the
+  checker is the guarantee, and divergence is detected and repaired rather than silently
+  accumulating. The exact sampling rate / digest granularity is an implementation spike (§12).
+
+### 8.8 Cache freshness & invalidation
+
+Replication-projection caches remote shard content; cache invalidation is the actual hard part
+and was missing from the first draft (review C-2). The protocol is **per-binding, driven by the
+capability profile**, with one rule: **freshness is always represented, never assumed** — every
+cached page's provenance envelope carries `(observed-at, source-rev-if-known, staleness-state)`,
+so a consumer can always tell live from stale.
+
+**Three invalidation modes, chosen by capability, not hard-coded:**
+
+| Mode | When | Mechanism |
+|------|------|-----------|
+| **Event-driven (push)** | shard has `notify` | a change event invalidates exactly the affected entries and enqueues a delta refresh (§8.7); the preferred mode |
+| **Validator poll** | shard exposes ETag / Last-Modified / rev | conditional fetch (`If-None-Match`); cheap "still fresh?" checks without transferring bodies |
+| **TTL** | shard offers neither | time-bounded staleness; the floor mode (Oddmuse-class shards) |
+
+Most real bindings are **hybrid**: event-driven for invalidation + a long TTL as a safety net
+for missed events + validator polls on read when an entry is past a soft age.
+
+**Operational-envelope coupling.** The mode is constrained by axis-10: a **rate-limited** shard
+(Notion) *must* favour event-driven + long TTL and *must not* poll per-read — the freshness
+policy is capability-gated like everything else. A local file shard can watch the filesystem
+(near-instant invalidation, effectively event-driven for free).
+
+**Thundering-herd / coalescing.** Concurrent reads of the same stale entry trigger a **single
+in-flight refresh** (single-flight); other readers await it or are served the stale-but-labelled
+value per policy. Bulk invalidations (a shard-wide event) are **batched and rate-shaped** to the
+shard's envelope rather than fired as N concurrent fetches.
+
+**Staleness is a policy knob, not a correctness bug.** Whether a reader gets *stale-but-fast* or
+*blocks-for-fresh* is a §10 preset (per space or per request); either way the envelope tells the
+truth about what was served. This is union-without-erasure applied to time.
+
+---
+
+## 9. Cross-cut — Authorization (L5)
+
+Fully specified in **`ArchitectureBlueprint.md`** (the access & history sub-blueprint);
+summarised here for completeness:
+
+- **One core, a ladder of modes** L0 (open/c2, zero deps) → L1 (attributed) → L2
+  (authenticated) → L3 (role/group) → L4 (multi-tenant enterprise). Climbing is configuration,
+  not re-architecture.
+- **PEP** wraps every adapter op; **PDP** decides `(principal, action, target)` over actions
+  `read/write/patch/merge/administer`, layered on the adapter's capability profile (a shard
+  that can't write can't be written regardless of policy — L5 consults the L1 rail).
+- **Authentication delegated** to a pluggable IdentityProvider (null provider = L0 default);
+  real identity from `user-engine` over `net-kingdom` IAM.
+- **Fail open only at L0, fail closed at L2+.** Authorization is pure/offline once a Principal
+  is resolved. Provenance carries authz context so the union never leaks unreadable content
+  (the L5↔provenance-rail interaction).
+
+### 9.1 Tenant isolation of the derived tier (review B-3)
+
+Read-time authz filtering is necessary but **not sufficient** when the derived tier is
+*persisted*: a single cross-tenant union/index cache guarded only by a filter on read is a
+standing leak surface (one filtering bug exposes another tenant's content). So isolation is
+**structural, not just procedural**:
+
+- **The derived tier is partitioned per tenant / root entity.** A tenant maps to a root entity
+  (§4); its union graph, equivalence index, projections, and caches live in a **separate
+  partition** keyed by that tenant. There is no shared cross-tenant derived store to leak from.
+- **No cross-tenant equivalence by default.** Blocking/LSH (§8.7) operates *within* a partition;
+  cross-tenant equivalence is an explicit, authorised, opt-in federation between roots, never an
+  accident of a shared index.
+- **Read-time filtering remains, as defence-in-depth** — the provenance envelope's authz context
+  is still checked, so even within a partition a principal sees only what it may; partitioning
+  removes the *blast radius*, filtering removes the *fine-grained* leak.
+- **This reconciles I-2 with L5:** recomputability (a persisted-but-disposable derived tier) is
+  preserved *per partition* — each tenant's derived tier is independently rebuildable from that
+  tenant's canonical state — so isolation costs nothing in the rebuild model. At L0/L1 (single
+  tenant) there is one partition and the machinery is invisible.
+
+**Isolation invariant (add to §2 as I-13):** *derived state is partitioned by tenant; no
+derived artifact spans tenants except through an explicit, authorised cross-root federation.*
+
+---
+
+## 10. The policy surface (mechanism over policy, made concrete)
+
+I-7 only means something if the policy knobs are enumerated and kept *out* of core algorithms.
+The configurable presets are:
+
+- **Canonical-source policy** — chorus / designated-canonical / git-merge / overlay-only /
+  vote-to-merge (per space or per equivalence set).
+- **Federation model** — the §8.3 taxonomy, per space, composable per shard.
+- **Shard mode** — read-only / write-through / mirrored / projected / cached / canonical
+  (constrained by the capability profile).
+- **Reconciliation cadence & conflict exposure** — push/poll/manual; show-conflicts vs
+  auto-merge-when-supported.
+- **Conflict-resolution preset** — chorus / designated-canonical / git-merge / vote-to-merge /
+  overlay-only (the *resolution* policy over §8.6's core detection; per space or equivalence set).
+- **Freshness / invalidation mode** — event-driven / validator-poll / TTL / hybrid, and
+  stale-but-fast vs block-for-fresh on read (§8.8; constrained by the operational envelope).
+- **History compaction** — squash policy for low-value churn, gc/repack cadence, per-shard
+  offload (§8.1), always preserving recoverable endpoints.
+- **Tenant partition mapping** — tenant ↔ root-entity, and any explicit cross-root federation
+  (§9.1, I-13).
+- **Execution policy** — derive/execute off (default) / sandboxed / per-shard-allowed.
+- **Authorization mode** — the L0–L4 ladder.
+- **Projection materialization** — lazy/eager; snapshot vs view-time; recording retention.
+
+Core ships sane defaults (L0 open; fork+journal; lazy replication-projection; event-driven+TTL
+freshness; overlay-before-mutation; execution off; one tenant = one root) and never hard-codes
+any of the above. (**Preset bundles** that package coherent knob-sets per persona are tracked
+as O-8, §12 — flexibility without bundles is operator burden.)
+
+---
+
+## 11. Concrete module structure (bridge to implementation)
+
+A proposed package layout for `src/shard_wiki/`, mapping 1:1 to the layers so the dependency
+rule (downward only; the derived tier is incrementally maintained, rebuild = fallback) is
+enforceable by import lint:
+
+```
+src/shard_wiki/
+  model/          # L2 top waist: Page, Identity, Placement, ProvenanceEnvelope,
+                  #   Span, the page-shape types; capability-spectrum value types
+  adapters/       # L1 bottom waist: AdapterContract (versioned iface), CapabilityProfile,
+                  #   attachment-mode binding; concrete adapters:
+    git/  folder/  gitea/  obsidian/  webdav/  notion/  …   # each: profile + verbs
+  coordination/   # L3: DecisionLog (append-only, git-backed, per-space append authority/
+                  #   lease), OverlayEngine (draft→patch→MR), reconcile
+                  #   (current coordination state = a derived fold → lives in union/)
+  federation/     # L3: FederationModel strategies (fork_journal, vcs_ping,
+                  #   graph_join, feed, activitypub, engine_mirror)
+  union/          # L4 (derived): IdentityResolver, EquivalenceGraph, UnionGraph,
+                  #   Transclusion (reference-not-copy)
+  projection/     # L4 (derived): ReplicationProjection, DerivationProjection,
+                  #   ViewRegistry (moldable), QueryIndex (delegate|derive)
+  authz/          # L5 cross-cut: PDP, PEP, IdentityProvider iface, NullProvider
+  provenance/     # cross-cut LEAF: ProvenanceEnvelope type + ⊕ (effective) only — pure data
+  policy/         # cross-cut LEAF: the §10 policy surface (presets + a resolve() read by
+                  #   coordination/federation/projection/authz); owns NO mechanism
+  api/            # L6: orchestrator API (server-side union for agents/CLI)
+```
+
+**The cross-cutting rails are leaves, not god-modules (review D-4).** `provenance/` and
+`policy/` are imported widely, so they are the highest coupling risk; the discipline that caps
+it is: **they may import *nothing* in the tree and contain *only* stable data types + pure
+functions** (the envelope and its `⊕`; the policy presets and a `resolve(question) → choice`).
+Mechanism never lives in a rail — `policy/` says *what* the preset is, `coordination/`/
+`projection/` decide *how* to honour it. A change to a rail is then a change to a small, stable,
+dependency-free leaf, not a ripple through every layer. Capability-spectrum value types live in
+`model/` (also leaf-like) for the same reason.
+
+Hard import rules (enforced by import lint):
+- `union/` and `projection/` may import `model/`, `adapters/`, `coordination/`, `policy/`,
+  `provenance/` — but **nothing may import them** (they are the disposable derived tier).
+- `model/`, `adapters/`, `provenance/`, `policy/` import nothing else in the tree (the waists
+  and rails stay thin); `provenance/` and `policy/` import nothing at all.
+- `coordination/` and `federation/` may import the waists + rails, never the derived tier.
+
+---
+
+## 12. Known scaling risks & open problems
+
+Tracked honestly rather than pretend-solved (review disposition F). Each has a **chosen
+direction** and a **revisit trigger** — the thing that, if observed, forces a redesign.
+
+| # | Risk / open problem | Chosen direction | Revisit trigger |
+|---|---------------------|------------------|-----------------|
+| O-1 | **Equivalence blocking misses true matches** (LSH false negatives, §8.7) | accept a small miss rate; curator bindings are the escape hatch | measured recall below an agreed threshold on real corpora |
+| O-2 | **Convergence bound for high-write CRDT shards under partition** (§8.6) | causal via journal + CRDT-native merge at the shard; no global bound promised | user-visible divergence that outlives a partition |
+| O-3 | **Per-equivalence-set divergence tracking** (§8.6) | start with base-rev comparison; add vector clocks only if needed | 3-way concurrent divergence that base-rev mis-orders |
+| O-4 | **Persisted derived-tier cost ceiling** (§8.7/§9.1) | per-tenant partition, incremental-maintained, rebuild is fallback | a tenant whose incremental cost still exceeds budget |
+| O-5 | **Axis-interaction completeness** (§6.5) | the named interaction table is the contract; extend deliberately | a real adapter needing an interaction not in the table |
+| O-6 | **Span-address portability across projection** (§7.2) | shard-scoped native-id wrapping now; tumbler later | cross-shard transclusion that native ids can't satisfy |
+| O-7 | **Squash-compaction vs. perfect auditability** (§8.1) | compact the *path*, preserve reachable states; configurable | a compliance need for every intermediate keystroke |
+| O-8 | **Policy-knob proliferation → operator burden** (§10) | ship named **preset bundles** ("personal vault" / "team wiki" / "enterprise federation") over the policy surface | operators mis-configuring interacting knobs |
+| O-9 | **Shard sharing across roots vs tenant partition** (§9.1, I-13) | shard exclusive to one root by default; explicit shared-read binding otherwise (avoids double-caching a rate-limited shard) | a shard legitimately needed live in two tenants |
+| O-10 | **Span-level authz under transclusion** (aggregation/inference leak; ⊕ across boundaries, §7.3/§9) | a transcluded span inherits the **stricter** of source & host authz; provenance ⊕ composes the source-page envelope under the host | a real cross-authz transclusion |
+| O-11 | **Union under shard unavailability** (§8.8 covers stale, not down) | **partial union** + per-shard "unavailable" provenance + last-known-projection where policy allows | an SLA need on partial reads |
+| O-12 | **Per-space append-log throughput ceiling** (§8.1 append authority) | single writer per space scales across spaces; per-space log sharding if needed | a single space exceeding one writer's append rate |
+
+These are the spec-writing inputs for `SHARD-WP-0002`; none blocks the architecture, each
+scopes an implementation spike.
+
+---
+
+## 13. Canonical data flows (the architecture exercised)
+
+**A. Attach a shard.** Adapter binds (chosen attachment mode) → probes/declares a capability
+profile → core registers the shard under a root entity → if not git-native, the coordination
+journal is seeded (begin-now/mirror/import per axis 5). No union rebuild yet (lazy).
+
+**B. Read a page through the union.** Consumer asks the union for an identity → Identity
+resolver maps it to placements across shards → equivalence yields chorus or canonical →
+replication-projection lazily fetches from each shard (cache + freshness) → page returned
+wrapped in its provenance envelope → L5 filters anything the principal can't see at source.
+
+**C. Edit a read-only / limited shard.** Write request → L5 PDP allows → capability profile
+says < write-through → OverlayEngine records a draft → renders a patch/MR in the shard's native
+syntax (lossless) or Markdown (lossy-with-report) → on explicit apply, commit to the journal
+and (if the profile permits) propagate; otherwise the overlay stands as the local truth, fully
+attributed.
+
+**D. Attach a computational notebook.** Adapter declares profile (attachment=file-store,
+opacity=mixed, computational=captured-output). Core attaches the `.ipynb` **source** as
+canonical; presents cells + embedded outputs as **derivation-projection snapshots** marked
+"run N, env unguaranteed"; offers a static render via the view registry; re-execution stays
+gated off. History uses paired-text/nbdime per axis 5.
+
+---
+
+## 14. Key tradeoffs & decisions
+
+Decided:
+
+- **Capability spectra over a verb checklist** — richer contract for precise, uniform
+  degradation; tamed by an orthogonal core + implied positions + a named interaction table
+  (§6.5). (Decided.)
+- **Three states; derived = f(canonical)** — sharded + coordination canonical, derived
+  disposable (§1). (Decided; supersedes the earlier "edges vs middle" framing.)
+- **Event-sourced coordination, one append authority per space** — coordination-canonical state
+  is an append-only **decision log** in the git journal; current state is a derived fold; a
+  per-space append lease gives a totally-ordered log and read-your-writes across orchestrator
+  instances (§8.1). (Decided — resolves the single-vs-multi-writer keystone.)
+- **Profiles are verified, not asserted** — a versioned **conformance suite** gates adapter
+  admission; capability-as-data acts on verified data (§6.6). (Decided.)
+- **I-2 is eventually-verified** — incremental maintenance is the fast path; a digest +
+  background consistency-checker detects and self-heals drift (§8.7). (Decided.)
+- **Incremental-first, rebuild-as-fallback** — the derived tier is continuously maintained from
+  change events; full rebuild is rare and need not be cheap (§8.7). (Decided — resolves the
+  earlier "union graph persistence" open item: **persisted, per-tenant, incrementally
+  maintained, rebuildable**, §9.1.)
+- **Identity ≠ fingerprint** — page identity is a stable handle; fingerprints are for
+  equivalence (§7.2). (Decided.)
+- **Consistency = read-your-writes (journal) + causal (derived) + eventual/freshness-labelled
+  (shards)**; conflict detection/representation is core, resolution is policy (§8.6). (Decided.)
+- **Address scheme** — shard-scoped native-id wrapping now; portable tumbler later (§7.2, O-6).
+  (Decided.)
+- **Default federation = fork+journal over Git**; other models opt-in (§8.3). (Decided.)
+- **Execution off by default** — recognise+project always; execute only when gated (§8.5). (Decided.)
+- **Derived tier is tenant-partitioned** (I-13, §9.1). (Decided.)
+
+Still open (carried to §12 / policy):
+
+1. **L1 "attributed-but-open" mode** — ship it or jump L0→L2? (Carried from ArchitectureBlueprint.)
+2. **Per-page ACL default** — off (per-shard/namespace) confirmed; revisit only if demand appears.
+3. The implementation spikes in **§12** (O-1…O-7).
+
+---
+
+## 15. What this architecture is *not*
+
+- Not a wiki engine, UI, or rendering pipeline (those are consumers at L6).
+- Not a canonical-source-of-truth — shards keep sovereignty; the middle is derived.
+- Not a generic file-sync daemon — synchronisation is wiki-page-semantic.
+- Not an execution platform — computation is recognised and projected, not hosted.
+- Not a universal ontology — no single schema is imposed on all shards.
+- Not an authentication/identity store — that is delegated (authorization is owned).
+
+---
+
+## 16. Traceability
+
+- **INTENT** — every invariant in §2 (I-1…I-13) cites an INTENT principle or boundary; no
+  invariant contradicts the Stability Note.
+- **Review & hardening** — this revision folds in
+  `history/260615-core-architecture-blueprint-review.md` via **`SHARD-WP-0005`**: A-1→§1/§3/§4
+  (three-state re-frame), B-1→§7.2 (identity vs equivalence), B-2→§8.6 (consistency/conflict),
+  B-3→§9.1+I-13 (tenant isolation), C-1/C-2→§8.7/§8.8 (incremental + indexed + invalidation),
+  C-3→§8.1 (history scaling), D-1→§6.5 (orthogonal core), D-2→§7.3 (layered provenance),
+  D-3→§8.4 (common-case projection), D-4→§11 (policy module + rail discipline); open items→§12.
+- **Round-2 review & hardening II** — folds in
+  `history/260615-core-architecture-blueprint-review-2.md` via **`SHARD-WP-0006`**:
+  A-1…A-4→§3/§4/§10/§11 (overview reconciled to the body), B-1+B-3→§8.1 (event-sourced
+  coordination + per-space append authority), B-2→§6.6 (adapter conformance suite),
+  B-4→§8.7 (incremental retraction/propagation + I-2 digest/checker); C-1…C-4→§12 (O-8…O-11).
+- **Research** — §6 (spectra) ← `260614-shard-spectrum-synthesis` v3; §8.3 (federation
+  taxonomy) ← v3 §2.5; §8.4–§8.5 (two-axis projection, view registry, computational scope) ←
+  `260614-computational-page-model-synthesis`; §7 page shapes ← the engine + modern-tool +
+  computational dives; §1 thesis ← the files-canonical/index-derived through-line across
+  Logseq/ikiwiki/GT/Pharo/Jupyter.
+- **Use cases** — the architecture is sized to UC-01–UC-84: federation/coordination (UC-01–07,
+  26–33, 56, 71–72, 79) → §8; attachment/adapter (UC-34–43, 50, 53, 57, 60–62, 64–66, 68–70,
+  76–82) → §6; page model & fidelity (UC-34, 39, 42, 55, 58–59, 67, 73, 80, 83–84) → §7/§8.5;
+  addressing/identity/query (UC-32, 44–49, 51–52, 54, 63, 74) → §7.2/§8.4; provenance &
+  metadata (UC-24–25, 75) → the provenance rail; collaboration & discovery (UC-08–23) → L6
+  consumers over the union.
+- **Workplans** — §6–§8 are the design target of `SHARD-WP-0002` (T11–T18); §9 is owned by
+  `ArchitectureBlueprint.md`; §1 (yawex-derived resolution/overlay) aligns with
+  `SHARD-WP-0001`.
+
+---
+
+## 17. Stability note
+
+This document defines shard-wiki's **internal** architecture; it may evolve as the spec
+workplans land. But the **thesis (§1)**, the **invariants (§2)**, and the **dual narrow waist
+(§1, §6, §7)** are load-bearing — changing any of them is an architectural change in the sense
+of INTENT's Stability Note and should be rare and deliberate.

spec/FederationArchitecture.md

@@ -0,0 +1,220 @@
+# FederationArchitecture
+
+Status: **draft for review** · Date: 2026-06-15 · Deliverable of **SHARD-WP-0002** (T1–T10, T17)
+
+The federation **design decisions** for shard-wiki: *what the union does*. It records, per
+topic, a decision with rationale, tradeoffs, and a **Decided / Deferred / Open** footer. It
+**references** `spec/CoreArchitectureBlueprint.md` (the whole-system architecture) and
+`spec/FederationRequirements.md` (yawex-derived ADRs) rather than restating them; the adapter
+contract (*what a backend must expose*) is the companion deliverable in
+`spec/TechnicalSpecificationDocument.md` §A (T11–T16, T18). UC references → `UseCaseCatalog.md`.
+
+Cross-cutting invariants assumed throughout (blueprint §2): orchestrator-not-engine (I-1),
+three-state canonical/derived (I-2), capability-as-data (I-3), union-without-erasure (I-4),
+overlay-before-mutation (I-5), git-addressable coordination (I-6), mechanism-over-policy (I-7),
+graceful degradation (I-8), identity≠placement (I-9), history-as-floor (I-10), authz-in-core
+(I-11), tenant-partitioned derived state (I-13).
+
+---
+
+## T1 — Orchestrator positioning & boundaries
+
+**Decision.** shard-wiki is an **adapter-layer orchestrator** in a **star** shape (many
+sovereign shards ↔ one information space), **not** a homogeneous federation network. It
+**compares, does not equate** (Federated Wiki homogeneous JSON sites, ikiwiki homogeneous git
+wikis, ActivityPub activity streams are *models it can speak*, §T17 — not shapes it imposes).
+Core owns: the union, the coordination journal, projection, overlay, resolution, authorization.
+Adapters own backend specifics; UI and editorial policy live outside core. (Blueprint §1, §5;
+UC-02, UC-26.)
+
+*Decided:* star orchestrator; compare-not-equate; core/adapter/UI/policy boundaries.
+*Deferred:* the reference UI (L6) is out of scope here. *Open:* none.
+
+## T2 — Remix primitives: reference / projection / overlay / import-fork
+
+**Decision.** Four primitives, escalating in commitment; **overlay-before-mutation is the
+default write path** (I-5), fork is *one federation model* (§T17) not the default for editing:
+
+| Primitive | Trigger | Writes remote? | Coordination-canonical? |
+|-----------|---------|----------------|--------------------------|
+| **Reference** | link only | no | no (a link in content) |
+| **Projection** | read remote page | no (cache) | no (derived) |
+| **Overlay** | edit a sub-write-through shard | not until explicit apply | **yes** (decision log) |
+| **Import / fork** | copy into a writable shard / fork-with-provenance | source unchanged | **yes** (fork event) |
+
+(Blueprint §8.2; FederationRequirements ADR-05; UC-04, UC-26, UC-29.)
+
+*Decided:* the four primitives + overlay-default. *Deferred:* fork-attribution portability
+format. *Open:* whether "import" and "fork" are one primitive with a flag or two (impl spike).
+
+## T3 — Equivalent-page identity & multi-version presentation
+
+**Decision.** Separate **identity** (stable handle), **placement** (N paths/shards), and
+**equivalence** (content-fingerprint / span-set overlap *across* identities), per
+FederationRequirements ADR-01/ADR-02 (I-9). Equivalence signals: normalized title/path, alias
+table (coordination-canonical), link-graph overlap, fingerprint, **curator binding**. Default
+presentation = **chorus-of-voices** (all equivalent versions, attributed); **designated-
+canonical** is a policy preset (§T9). Divergence is data in the provenance envelope (I-4),
+detected as core mechanism (blueprint §8.6). (UC-07, UC-27; UC-46.)
+
+*Decided:* identity/placement/equivalence split; chorus default. *Deferred:* fingerprint
+algorithm + blocking params (blueprint O-1). *Open:* curator-binding UX (L6).
+
+## T4 — History, attribution & the coordination journal
+
+**Decision.** Each information space has a **git-addressable, event-sourced coordination
+journal** (blueprint §8.1, I-6/I-10): coordination-canonical decisions (overlay/binding/alias/
+merge/fork) are append-only events; current state is a derived fold. **One append authority per
+space** gives a total order (read-your-writes across instances). Per-shard native history is
+**adopted** (git-native), **supplemented** (DB/CRDT internal → journal begins-now/mirrors), or
+**imported** (open file history backfilled) per the history-portability axis (TSD §A T13).
+Attribution is portable on the event (UC-29). (UC-29, UC-33.)
+
+*Decided:* event-sourced journal + per-space append authority + adopt/supplement/import.
+*Deferred:* per-space log sharding for extreme write rates (blueprint O-12). *Open:* none.
+
+## T5 — Union composition layer
+
+**Decision.** The **server-side orchestrator union is primary** — the derived tier (union
+graph, indexes, projections) is composed in core for agents/CLI/non-browser consumers
+(blueprint §8.4), **incrementally maintained** (not recomputed, §8.7), **tenant-partitioned**
+(I-13). **Client-side composition** (Federated-Wiki-style browser pull) is a supported
+*consumer pattern over the same union*, not the only path. Freshness/caching per §8.8. (UC-05,
+UC-27, UC-03, UC-31.)
+
+*Decided:* server-primary, client-optional; incremental, partitioned. *Deferred:* client
+SDK shape. *Open:* persisted-union digest granularity (blueprint O-4, B-4 checker).
+
+## T6 — Change notification & subscription transports
+
+**Decision.** Change-notification is an **optional adapter capability** (`notify`), and it is
+the **primary driver of incremental maintenance** (blueprint §8.7/§8.8). Transports, per
+profile: git hook / ikiwiki-style ping, ActivityPub Create/Update, webhook, WebDAV/HTTP ETag
+or `Last-Modified` poll, plain polling fallback. A notification → invalidate affected entries
++ enqueue delta refresh + a RecentChanges union entry (FederationRequirements ADR-03; UC-31,
+UC-17). Rate-limited shards favour event-driven + long TTL (operational-envelope axis).
+
+*Decided:* notify = optional capability, drives incremental + RecentChanges; transport per
+profile. *Deferred:* ActivityPub as content-bearing (vs notify-only) — start notify-only.
+*Open:* fediverse-dependency posture for v1.
+
+## T7 — Information-space lifecycle
+
+**Decision.** Root entities have lifecycle states: **active → read-only-archived → retired
+(detached)**, and **merged-into-successor**. **Carry-forward** is selective import from an
+archived shard (UC-28, UC-30). **Space-fork / branch** (UC-33) = branch the coordination
+journal + shard-config (a fork event, §T2/§T17 fork+journal model). Retirement **preserves
+read-only union entries** by default (history-as-floor, I-10), never hard-deletes projections.
+(UC-28, UC-30, UC-33.)
+
+*Decided:* the lifecycle states + carry-forward + space-branch; retire-preserves. *Deferred:*
+ephemeral "happenings" as a first-class mode. *Open:* GC policy for retired-space derived tier.
+
+## T8 — Transclusion & projection depth
+
+**Decision.** Transclusion is **one reference-not-copy primitive** over the addressable union
+(blueprint §8.4), at three depths:
+
+| Level | UC | Behaviour |
+|-------|-----|-----------|
+| Whole-page projection | UC-03 | lazy full page from a remote shard (replication-projection) |
+| Block/span transclusion | UC-32 | inline embed by span address, with origin + freshness |
+| Link reference | UC-08 | pointer only (ADR-06) |
+
+Every transcluded artifact carries provenance + **staleness** (I-4, §8.8); live-transclusion
+fragility (link rot / remote down) degrades to last-known + an `unavailable`/`stale` marker
+(blueprint O-11). Span-level authz under transclusion = the stricter of source/host (O-10).
+Reference-not-copy unifies Xanadu transclusion, ZigZag clone, embeds, synced blocks, Trilium
+note-clone, literate named-chunk. (UC-03, UC-32.)
+
+*Decided:* one primitive, three depths, provenance+staleness mandatory. *Deferred:* snapshot-
+on-import vs live default (a policy). *Open:* span-authz composition (O-10), addressing (O-6).
+
+## T9 — Consensus & reconciliation policy catalog
+
+**Decision.** **Detection is core, resolution is policy** (I-7, blueprint §8.6). Core always
+detects divergence and represents it as a coexisting (chorus) set; the **resolution preset** is
+configurable per space / per equivalence set:
+
+- **chorus-spread** (versions coexist; default) · **designated-canonical** (explicit write
+  target) · **git-merge** (where merge capability allows) · **vote-to-merge / editorial gate**
+  (optional, L6-assisted) · **overlay-only** (no destructive merge on read-only sources).
+
+(FederationRequirements ADR-03/ADR-05; UC-07, UC-27.)
+
+*Decided:* the preset catalog; detection-core/resolution-policy. *Deferred:* vote/editorial
+gate mechanics (L6). *Open:* default preset per persona bundle (blueprint O-8).
+
+## T10 — Federation-operations capability matrix
+
+**Decision.** Each federation operation requires a minimum **verified capability profile**
+(TSD §A T11/§6.6); below it, the op **degrades** along the named interaction axes (blueprint
+§6.5) rather than failing. The matrix (consuming the T11 vocabulary):
+
+| Federation op | Min capabilities | Degradation when absent |
+|---------------|------------------|--------------------------|
+| **read / project** | `read` | (floor — every shard) |
+| **transclude span** | `read` + addressing≥span | whole-page projection only |
+| **overlay** | `read` | always available (overlay is local) |
+| **write-through** | `write` (+ `merge` for concurrent) | → overlay/patch target |
+| **diff / 3-way merge** | `diff`,`merge` | → keep-both / chorus |
+| **notify-driven freshness** | `notify` | → validator-poll → TTL (§8.8) |
+| **native search delegate** | native-query≥index | → derived index over projection |
+| **publish / mirror** | `publish` | → read-only / static projection |
+| **fork+journal federation** | `read` + history (any) | → projection-only participant |
+
+Every backend, down to the Oddmuse flat-file floor, is usable as **read-only / cache /
+projection / backup / patch target** (I-8). This matrix and the T11 spectra are kept in sync
+(it consumes that vocabulary). (UC-02–UC-07.)
+
+*Decided:* the op→capability matrix + degradation paths. *Deferred:* exhaustive per-op test
+vectors → the conformance suite (§6.6). *Open:* axis-interaction completeness (blueprint O-5).
+
+---
+
+## T17 — Federation-model taxonomy (selectable / composable)
+
+**Decision.** Federation is **plural and composable**, not one mechanism (blueprint §8.3). A
+space selects a model (composing per shard); the default is **fork+journal over Git** (the home
+case):
+
+| Model | Anchor | Coordination shape | Capability floor | UCs |
+|-------|--------|--------------------|------------------|-----|
+| **Fork + journal** *(default)* | Federated Wiki | copy-with-provenance + per-page action journal (story = replay) | `read` + journal | UC-26, UC-71, UC-72 |
+| **VCS-replication + ping** | ikiwiki | git clone/pull/push + change-ping | git-IS-store | UC-31, UC-33, UC-79 |
+| **Query-time graph-join** | Wikibase `SERVICE` | join remote graphs at query, no copy | native-query≥graph | UC-74 |
+| **Feed aggregation** | RSS/Atom | inbound feed → pages | `read` | UC-03 |
+| **Activity streams** | ActivityPub | Create/Update events (notify or content) | `notify` | UC-31 |
+| **Engine-mirror** | Wiki.js DB↔Git | engine mirrors its store to git | `publish`/mirror | UC-68, UC-69 |
+
+The coordination journal (T4) is the fork+journal model's home; **git IS the journal** in
+VCS-replication and engine-mirror (forge wikis make git the store *and* journal, resolving the
+engine-mirror write-race). Models compose: e.g. fork+journal locally, query-join for a
+typed-graph shard, feed-aggregation for an external source. (Mechanism over policy, I-7.)
+
+*Decided:* the six models, selectable per space + composable per shard, default fork+journal.
+*Deferred:* activity-streams content-bearing mode. *Open:* multi-model interaction edge cases
+(when two models touch one shard).
+
+---
+
+## Consolidated decisions / deferred / open
+
+- **Decided (architecture-settling):** star orchestrator (T1); overlay-default remix (T2);
+  identity/placement/equivalence + chorus (T3); event-sourced journal + append authority (T4);
+  server-primary incremental union (T5); notify-driven freshness (T6); space lifecycle (T7);
+  reference-not-copy transclusion (T8); detection-core/resolution-policy preset catalog (T9);
+  op→capability matrix (T10); selectable/composable federation models (T17).
+- **Deferred (to impl / L6 / persona bundles):** reference UI; fork-attribution format; client
+  SDK; vote/editorial mechanics; ephemeral spaces; ActivityPub content-bearing; default-preset
+  bundles (O-8).
+- **Open (tracked in blueprint §12):** O-1 equivalence blocking, O-4 union digest, O-5 axis
+  interactions, O-6 addressing, O-8 presets, O-10 span-authz, O-11 unavailability, O-12 log
+  throughput.
+
+## Acceptance (SHARD-WP-0002 federation half)
+
+T1–T10 + T17 each have a decision record with a Decided/Deferred/Open footer; all honour INTENT;
+UC-26–UC-33, UC-56, UC-71–UC-72, UC-74, UC-79 trace here; the adapter-contract companion is
+`spec/TechnicalSpecificationDocument.md` §A (T11–T16, T18). Conflicts with SHARD-WP-0001 are
+none (FederationRequirements ADRs are consumed, not duplicated).

spec/FederationRequirements.md

@@ -0,0 +1,214 @@
+# FederationRequirements — yawex-derived design notes
+
+Status: **draft for review** · Date: 2026-06-15 · Deliverable of **SHARD-WP-0001**
+
+Concrete, ADR-ready design decisions for the union/federation layer, distilled from the yawex
+prior-art review (`research/260608-yawex-prior-art/findings.md`) and made **consistent with**
+`spec/CoreArchitectureBlueprint.md` (the whole-system architecture) and `INTENT.md`. yawex is
+*inspiration and a case checklist*, never an interface to inherit (decision 2026-06-08).
+
+These are **requirements** (what the union must do); `spec/FederationArchitecture.md`
+(SHARD-WP-0002) is the architecture that realises them. UC references are to
+`spec/UseCaseCatalog.md`.
+
+**Resolved precondition.** The yawex "minimal access model in core" thread is **settled**:
+authorization-in-core / authentication-delegated, the L0–L4 ladder — INTENT amended,
+`ArchitectureBlueprint.md` ratified. Auth is therefore *not* re-litigated here; these ADRs
+assume it (the resolver and overlay paths run behind the L5 PEP/PDP).
+
+---
+
+## ADR-01 — Cross-shard page resolution
+
+**Status:** accepted · **CoreArchitectureBlueprint:** §8.4 (union), §7.2 (identity)
+
+**Context.** yawex's most-tested component was `PageLookUp`, a context-relative resolver with
+ordered states `LOCAL, CLIMB, DROP, GLOBAL, REMOTE, SWITCH, JUMP, VIRTUAL, FAILED`. Decision
+(2026-06-08): **inspiration only** — use the states as a *checklist of cases*, design the
+federation resolver fresh.
+
+**Decision.** Resolution is a pure function over the derived union:
+`resolve(name, from_context, policy) → ResolutionResult`, evaluated in a defined order and
+keyed on **page identity** (the stable handle), not path (I-9):
+
+1. **Same-namespace, same-shard** exact identity match — *(yawex LOCAL)*.
+2. **Namespace walk** — climb/descend ancestor namespaces of `from_context` — *(CLIMB/DROP)*.
+3. **Union lookup** — match identity / alias-table entry across all attached shards — *(GLOBAL)*.
+4. **Equivalence set** — if several shards hold an equivalent page, return the **chorus set**;
+   the *canonical-source* policy preset (chorus / designated-canonical) decides presentation —
+   never silently pick one (union without erasure, I-4). *(implicit in yawex; explicit here.)*
+5. **Projection / virtual** — a page whose content lives in a remote shard (lazy replication,
+   *REMOTE*) or is computed/query-defined (derivation, *VIRTUAL*).
+6. **Explicit address** — a shard- or space-qualified reference resolves directly — *(SWITCH/JUMP)*.
+7. **Not found** → **red-link**: a resolvable *target* with no page yet, createable (UC-23) —
+   *(FAILED)*.
+
+`ResolutionResult` carries the resolved identity (or red-link), the placement(s), the
+provenance envelope (ADR-04), and — on ambiguity — the full chorus set. Resolution is a
+**derived-tier read** (union graph + equivalence index, §8.4); it is incremental-maintained and
+respects the L5 authz filter (a principal never resolves to content it can't see).
+
+**Consequences.** Deterministic, policy-driven, no privileged shard; every yawex state has a
+home without inheriting its structure. **Open:** cross-space `JUMP` addressing syntax ties to
+the portable-address scheme (CoreArchitectureBlueprint O-6).
+
+---
+
+## ADR-02 — Namespace / path model & shard roles
+
+**Status:** accepted · **CoreArchitectureBlueprint:** §7.2 (identity≠placement), §4 (shard mode)
+
+**Context.** yawex modelled **topics as directories** (a topic's gateway page shares the dir
+name) with relative (`../`) / absolute (`/`) paths and normalization, and page classes
+`local / global / virtual`.
+
+**Decision.**
+- The union exposes a **namespace tree**; a **path is a placement coordinate, not an identity**
+  (I-9). One identity may have **N placements** (paths/shards) → a DAG, no single canonical path.
+- **Path grammar:** relative (`../`, `./`) resolved against `from_context`; absolute (`/`)
+  against the space root; **normalization** (collapse `.`/`..`; case & separator handling) is a
+  per-space **policy** knob (§10) — defaulting to case-preserving, `/`-separated.
+- **yawex page classes → shard roles / modes:** `local → canonical`, `global → cross-cutting`
+  (a shard whose pages augment/overlay across namespaces), `virtual → projected/computed`. These
+  are the INTENT shard modes (read-only · write-through · mirrored · projected · cached ·
+  canonical), selected by policy, constrained by the capability profile.
+- Cross-shard name collisions are resolved by ADR-01's order + equivalence, not by a global
+  flat namespace.
+
+**Consequences.** The namespace is a navigable view over placements (a dimension of the union),
+not a storage layout. **Open:** per-space normalization policy defaults (case-sensitivity,
+unicode) — a policy preset, bundled per persona (O-8).
+
+---
+
+## ADR-03 — Union-level derived views: core vs adapter
+
+**Status:** accepted · **CoreArchitectureBlueprint:** §8.4 (derived query index), §8.7
+(incremental) · **resolves findings open-Q #3**
+
+**Context.** yawex shipped BackLinks, RecentChanges, AllPages, SiteMap, full-text Search.
+
+**Decision.** Each is a **derived-tier** view (rebuildable, incrementally maintained); classify
+by where it is computed:
+
+| View | Tier | Rationale |
+|------|------|-----------|
+| **BackLinks** | **core** | the link-graph over the union — squarely shard-wiki's concern (UC-18); the strongest core view |
+| **RecentChanges** | **core** | merge the coordination journal (§8.1) with shard change events (notify/poll, §8.8) across the union (UC-17) |
+| **AllPages / SiteMap** | **core** | an enumeration/projection of the union graph; cheap |
+| **Search (full-text)** | **hybrid** | **delegate** to a shard's native search where the native-query axis allows; **else** build a derived index over projections (the Logseq DataScript-over-files pattern, UC-19/UC-63) |
+
+All are computed in the derived tier and carry provenance; **presentation is L6 (UI)**, never
+hard-coded in core (mechanism over policy, I-7).
+
+**Consequences.** BackLinks/RecentChanges/AllPages/SiteMap are core deliverables; Search is a
+capability-gated delegate-or-derive. **Open:** cross-shard search ranking/relevance is a policy
+concern, not core mechanism.
+
+---
+
+## ADR-04 — Provenance & freshness model (concrete fields)
+
+**Status:** accepted · **CoreArchitectureBlueprint:** §7.3 (layered provenance), §8.8 (freshness)
+
+**Context.** yawex `Page::info` exposed modtime (and TODO'd last-editor / hits / edits). INTENT
+mandates explicit provenance & freshness (I-4).
+
+**Decision.** Concretise the **provenance envelope** (layered: page-level + span-level deltas):
+
+```
+ProvenanceEnvelope (page-level):
+  source_shard         # which shard this came from
+  source_rev?          # shard-native revision id, if the shard exposes one
+  observed_at          # when shard-wiki last read it
+  liveness             # static | captured-snapshot | live-over-files | view-time | irreducibly-live
+  staleness_state      # live | fresh | stale | unavailable
+  authz_context        # the L5 context under which it was read (no-leak, §9)
+  overlay_state        # none | draft | patch-pending | applied
+  divergence[]         # equivalence-set peers that differ (the chorus, ADR-01 step 4)
+  derivation_lineage?  # for derived/derivation-projection content (source → this view)
+Span-level: only the fields that differ from the page envelope (effective = page ⊕ delta).
+```
+
+`freshness = (observed_at, source_rev?, staleness_state)`; `unavailable` is the dead-shard
+state (feeds ADR-03 RecentChanges and the union-under-unavailability open item O-11). This
+envelope is the data behind union-without-erasure and the input to conflict display.
+
+**Consequences.** Provenance is queryable, layered (cheap per-span), and drives views/conflict
+UI. **Open / DROP:** hits/edits *analytics* are an L6/analytics concern, out of core (dropped
+from the yawex feature set).
+
+---
+
+## ADR-05 — Overlay / lightweight-patch model
+
+**Status:** accepted · **CoreArchitectureBlueprint:** §8.2 (overlay engine), §8.1 (decision
+log), §8.6 (apply-under-drift)
+
+**Context.** yawex had an append + threaded-comment workflow (edit a page without a full
+rewrite). INTENT mandates overlay-before-mutation (I-5).
+
+**Decision.** The overlay lifecycle for any shard below write-through capability:
+
+1. **Draft** — an edit becomes a draft recorded as a **coordination-canonical event** in the
+   space's decision log (§8.1); the unapplied overlay is the **local truth**, fully attributed
+   (`overlay_state`, ADR-04).
+2. **Patch / MR** — rendered in the shard's **native syntax (lossless)** or **Markdown
+   (lossy-with-fidelity-report)** per the translation axis.
+3. **Apply** — only on explicit intent, only where profile + policy permit, with
+   **apply-under-drift** semantics (§8.6: fast-forward / three-way / refuse-and-re-present).
+4. **Append / comment** = a **constrained overlay subtype** (purely additive, low-conflict) —
+   the direct generalisation of yawex's workflow; safe even on the most limited shards.
+
+This makes read-only, rate-limited, and lossy shards **editable** without silent remote
+mutation (graceful degradation, I-8; no silent mutation).
+
+**Consequences.** One overlay mechanism spans drafts, patches, MRs, and comments; storage is the
+decision log (no separate store). **Open:** whether threaded-comment threading is a first-class
+overlay subtype or a generic structured-append — defer to implementation.
+
+---
+
+## ADR-06 — Markdown link semantics (wikilink + red-link)
+
+**Status:** accepted · **CoreArchitectureBlueprint:** §7 (page model), ADR-01 (resolution) ·
+**resolves findings open-Q #2**
+
+**Context.** yawex had CamelCase WikiLinks, `[[free links]]`, red-`?` links for nonexistent
+pages, `::` labels. INTENT mandates Markdown-first; TRANSFORM the *semantics*, drop the bespoke
+syntax.
+
+**Decision.**
+- Adopt a **CommonMark wikilink extension**: `[[Target]]` / `[[Target|label]]`, resolved via
+  ADR-01 (by identity/name across the union).
+- **Red-link** = a wikilink whose target resolves to FAILED (ADR-01 step 7): a valid,
+  *createable* target with no page yet (the soft-create affordance, UC-23).
+- **CamelCase auto-linking is OFF by default** (a legacy affordance); opt-in **per space** for
+  migrating CamelCase wikis (UseModWiki/c2 lineage, UC-25).
+- Links are stored **as text** (git-diffable; structure/links federate iff in-text).
+- **Boundary (resolves open-Q #2):** the link **model + resolution is core**; the **visual
+  rendering** of wikilinks/red-links is a **reference-UI (L6)** concern. Core decides *what a
+  link resolves to and whether it's a red-link*; the UI decides how it looks.
+
+**Consequences.** Markdown-first, backend-neutral, resolution-unified with ADR-01. **Open:**
+cross-shard wikilink target disambiguation syntax ties to the portable-address scheme (O-6).
+
+---
+
+## Coverage & open questions
+
+- **Findings open-Q #1** (per-page vs per-shard ACL) — answered by the settled access model:
+  per-shard / per-namespace default, per-page ACL opt-in at L4 (`ArchitectureBlueprint.md`).
+- **Findings open-Q #2** (wikilink core vs UI) — ADR-06: model/resolution core, presentation UI.
+- **Findings open-Q #3** (derived views core vs adapter) — ADR-03.
+- Carried to CoreArchitectureBlueprint §12: cross-space addressing syntax (O-6), namespace
+  normalization presets (O-8), cross-shard search ranking (policy), union-under-unavailability
+  (O-11).
+
+## Acceptance (SHARD-WP-0001)
+
+Each task T1–T6 has an ADR (T1→ADR-01, T2→ADR-02, T3→ADR-03, T4→ADR-04, T5→ADR-05, T6→ADR-06);
+all honour INTENT (mechanism over policy, union without erasure, overlay before mutation,
+capability-aware adapters) and are consistent with `CoreArchitectureBlueprint.md`. The
+access-model thread is ratified (not deferred). The next implementation workplan (domain model /
+adapter contract) can proceed without unresolved yawex-derived design gaps.

spec/README.md

@@ -6,10 +6,15 @@ Background on document types: InfoTechPrimers on coulomb.social.
 
 | File | Status | Role |
 |------|--------|------|
+| `CoreArchitectureBlueprint.md` | draft for review | **Whole-system architecture** — layers, abstractions, load-bearing decisions (synthesised from all research) |
+| `FederationArchitecture.md` | draft for review | federation design — *what the union does*: T1–T10 decision records + the federation-model taxonomy (SHARD-WP-0002) |
+| `WikiEngineCoreArchitecture.md` | draft for review | the native **headless, API-first wiki engine** — small page-store kernel + typed-extension framework, as a canonical-mode shard backend (SHARD-WP-0013) |
+| `adr/` | living | Architecture Decision Records (ADR-0001: engine activation via feature-control) |
+| `FederationRequirements.md` | draft for review | yawex-derived union/federation design notes — resolution, namespace, derived views, provenance, overlay, links (ADR-01…06; SHARD-WP-0001) |
 | `ProductRequirementsDocument.md` | draft scaffold | What the product must deliver |
-| `TechnicalSpecificationDocument.md` | draft scaffold | How the system is built |
-| `UseCaseCatalog.md` | draft | 25 use cases promoted from c2 + yawex research |
-| `ArchitectureBlueprint.md` | draft | Access, history, and identity architecture |
+| `TechnicalSpecificationDocument.md` | draft + §A | How the system is built; **§A = the normative shard adapter contract** (T11–T16, T18; SHARD-WP-0002) |
+| `UseCaseCatalog.md` | draft | 84 use cases promoted from c2 + yawex + ~23-system research |
+| `ArchitectureBlueprint.md` | draft | Access, history, and identity sub-blueprint (the L0–L4 authorization ladder; referenced by CoreArchitectureBlueprint §9) |
 
 Promote material from `research/` and reviewed items from `demand/` into spec
 before treating it as implementation authority.

spec/TechnicalSpecificationDocument.md

@@ -33,7 +33,134 @@ per information space.
 
 ## 4. Architecture References
 
-- `spec/ArchitectureBlueprint.md` — access, history, identity delegation
+- `spec/CoreArchitectureBlueprint.md` — whole-system architecture (layers, the dual narrow
+  waist, the 15 capability spectra, projection, consistency); the normative source for §A.
+- `spec/FederationArchitecture.md` — federation design (*what the union does*); §A is its
+  companion (*what a backend must expose*).
+- `spec/FederationRequirements.md` — yawex-derived ADRs (resolution, page model, overlay).
+- `spec/ArchitectureBlueprint.md` — access, history, identity delegation (L5).
+
+---
+
+# A. Shard Adapter Contract (normative)
+
+Deliverable of **SHARD-WP-0002** (T11–T16, T18): the versioned interface a backend implements
+to participate as a shard, and the *normative* rules core relies on. It is the **bottom narrow
+waist** (blueprint §6); the page model is the top waist (§7). This section is normative where it
+says **MUST/SHOULD**; design rationale lives in the blueprint (cited, not restated).
+
+## A.1 (T11) Capability model & versioned interface
+
+- The contract is a **versioned interface** (`Foswiki::Store`/`Foswiki::Meta` is the proof a
+  swappable-backend-behind-a-stable-interface works). A binding declares the contract version
+  it implements; core checks compatibility at registration.
+- **Operation verbs:** `read, write, diff, merge, lock, version, publish, notify,
+  transclude-source, translate-syntax, structured-payload, derive-projection, execute`. The
+  last two are **gated, OFF by default** (A.6/T18). Verb support is part of the profile and MUST
+  reconcile with the T10 federation-ops matrix.
+- **Capability profile = a position on each capability spectrum**, not a boolean checklist. The
+  full set is the **fifteen spectra** (blueprint §6.1); operationally they reduce to a **small
+  orthogonal core** (substrate, write-granularity, content-opacity, operational-envelope,
+  access-grant, computational/liveness) with the rest **implied** via published rules that
+  **forbid impossible profiles** (blueprint §6.5). Degradation reads only the **named
+  axis-interaction subset** (blueprint §6.5 table) — that table *is* the degradation contract.
+- A profile MUST express **absence** cleanly (the Oddmuse floor); core never guesses a missing
+  capability.
+
+## A.2 (T11/§6.6) Conformance — profiles are verified, not asserted
+
+- The contract ships a **versioned conformance suite**. A binding is **admissible only if it
+  passes**: the suite exercises each declared verb and spectrum position and checks observed
+  behaviour matches the claim (a `write` round-trips, `notify` actually fires, an opaque shard
+  refuses plaintext query, implied-position rules hold). A lying/buggy profile is **rejected at
+  registration**, not run in production (blueprint §6.6).
+- Conformance makes capability-as-data (I-3) and the §6.5 degradation contract **sound**.
+  Mismatch is reported as a capability-by-capability diff; an adapter may register
+  *degraded-but-honest* (drop the unsupported claim).
+
+## A.3 (T14) Adapter binding — attachment-mode taxonomy
+
+A backend MAY offer several modes; attach mode is a **per-binding, capability-gated choice**
+with one declared authoritative (blueprint §6.3):
+
+- **file-store** (native vault/folder *or* an interchange/sync mirror) · **git-IS-store** (forge
+  wikis & ikiwiki — git is store *and* journal; the home case) · **in-engine-hosted** (XWiki
+  component, Obsidian/Logseq/Roam plugin, Trilium script) · **local-REST** (Joplin Data API,
+  Trilium ETAPI) · **external-API-only** (Notion) · **direct-DB** (MojoMojo schema→model) ·
+  **CRDT-replica** (Anytype/AFFiNE/AppFlowy) · **P2P / no-central-endpoint**.
+- **Backend-swap tolerance:** identity/provenance MUST survive a substrate change (bind to
+  capabilities, not "it's files"). **Boundary:** an **image / live-memory blob is never an
+  attach target** (I-12) — participation is export→files only.
+- (UC-38, UC-40, UC-43, UC-50, UC-53, UC-57, UC-60, UC-62, UC-64, UC-65, UC-76, UC-79, UC-81.)
+
+## A.4 (T12) Page model — structured / computational payload
+
+The backend-neutral, Markdown-first page model MUST carry, without lossy flattening, every
+shape in blueprint §7.1: prose; typed/computed records (incl. effective-vs-own computed
+metadata); typed-graph statements (Wikibase); inline-embedded objects (Quip/Notion);
+non-Markdown assets (typed asset / opaque blob / content-type registry); and the **four
+computational shapes** (one-source-many-projections UC-83; notebook-with-embedded-output UC-84;
+program-as-page; live/temporal). All reduce to `(content|source, structure, provenance
+envelope, [derivation rule])`. **Identity is a stable handle; placement is separate; equivalence
+is fingerprint-based** (blueprint §7.2, FederationRequirements ADR-01/02, I-9). The **provenance
+envelope is layered** (page + span deltas; effective = page ⊕ delta, §7.3). (UC-34, UC-39,
+UC-55, UC-58, UC-54, UC-44, UC-66, UC-67, UC-73, UC-83, UC-84.)
+
+## A.5 (T13) History portability — adopt / supplement / import
+
+Per the history axis: **adopt** git-native history as-is; **supplement** non-portable internal
+history (DB / Notion / Joplin / Trilium revisions, CRDT-log) — the journal begins-now / mirrors
+/ snapshots; **import** open file history (RCS, PlainFile, MojoMojo DB-version-rows) backfilled
+preserving author/timestamp. **Partial/truncated history MUST be reported honestly** ("history
+begins at", UC-24), never implied complete. Embedded-output documents (notebooks) use
+paired-text (Jupytext) / cell-aware merge (nbdime). The space's own coordination history is the
+event-sourced decision log (blueprint §8.1). (UC-36, UC-41, UC-24.)
+
+## A.6 (T15) Syntax translation & content fidelity
+
+Translation is a spectrum: **native → lossless → lossy-with-fidelity-report**. Read native
+markup (TML, XWiki syntax, HTML) into the page model; accept Markdown overlays back via
+**lossless bidirectional translation** where possible (Foswiki WysiwygPlugin is the proof). For
+non-round-tripping models (Notion blocks, Trilium HTML, CRDT, typed-graph, notebook JSON/MIME):
+translate lossily but **make the fidelity loss visible** — a per-shard/per-page report of what
+projects cleanly vs degrades, with non-mappable elements preserved as provenance/sidecar (I-4).
+Add a **structured-re-evaluable-value** point to the opacity spectrum (Wolfram expression).
+Where no acceptable translation exists, the shard is a **read-only/projection** participant
+(I-8), never silently corrupted. (UC-42, UC-59, UC-03, UC-73.)
+
+## A.7 (T16) Addressing, identity & navigation
+
+- **Span addressing:** adopt native span IDs where minted (Roam `:block/uid`, Logseq `id::`,
+  Notion/CRDT UUID), shard-scoped so they survive projection and don't collide; else a
+  position address (path+range) or content-fingerprint address. Portable tumbler is the ideal
+  (blueprint O-6).
+- **Transclusion** = one reference-not-copy primitive over the addressable union (FederationArch
+  T8). **Query/navigation:** delegate to a shard's native query where capable (Datalog, DB
+  query, XWQL, SPARQL), **else build a derived index over the projection** (Logseq pattern);
+  dimensional/query-defined views are derived-tier. (UC-44–48, UC-51, UC-52, UC-54, UC-63,
+  UC-74.)
+
+## A.8 (T18) Computational / executable content capability
+
+**In scope as a page-model + projection concern; out of scope as an execution platform**
+(blueprint §8.5). Core **recognises** computational types, attaches the **canonical source**,
+and presents derived forms as **provenance- and liveness-marked projections**. `derive-
+projection`/`execute` are **gated capabilities, OFF by default**, carrying a **trust/sandbox**
+concern, **degrading to a captured snapshot / static render / recording**. One snapshot-
+provenance record (run id, source rev, timestamp, environment "unguaranteed") serves notebooks,
+renders, recordings. No INTENT amendment required. (UC-54, UC-55, UC-83, UC-84.)
+
+## A.9 Conformance & module mapping
+
+The contract maps to `src/shard_wiki/adapters/` (the bottom waist: `AdapterContract`,
+`CapabilityProfile`, attachment-mode binding, the conformance suite) consuming `model/`
+(page model + capability value types) and `provenance/` (blueprint §11). Each concrete adapter
+ships its declared profile + a conformance pass.
+
+*Decided:* A.1–A.8 (versioned capability contract, verified conformance, binding taxonomy,
+page model, history portability, translation, addressing, gated computational content).
+*Deferred:* per-backend adapter specs (one per backend, later). *Open:* blueprint §12 O-items
+(addressing O-6, axis interactions O-5, span-authz O-10).
 
 ## 5. Integration Boundaries
 
@@ -47,10 +174,13 @@ Package scaffold only (`__version__`, smoke tests). Domain model not yet coded.
 
 ## 7. Use Cases
 
-`spec/UseCaseCatalog.md` — 25 use cases (UC-01–UC-25) promoted from c2 wiki
-origins and yawex prior-art research.
+`spec/UseCaseCatalog.md` — 84 use cases (UC-01–UC-84) from c2/yawex origins,
+the wiki-engine + modern-tool + computational research, and the syntheses.
 
 ## 8. Next Specification Work
 
-Outputs from `SHARD-WP-0001` tasks (page resolution, namespaces, derived views,
-provenance, overlays, link semantics) will be incorporated here as they complete.
+The design layer is complete: `SHARD-WP-0001` (→ `FederationRequirements.md`),
+`SHARD-WP-0002` (→ `FederationArchitecture.md` + §A above), and the hardened
+`CoreArchitectureBlueprint.md`. The next workplan is the **implementation** of the
+domain model + adapter contract (starting from §A and blueprint §11's module layout),
+likely with a first spike on the keystone (the event-sourced decision log + derived fold).

spec/UseCaseCatalog.md

@@ -45,6 +45,71 @@ of the shard-spectrum work; E–G carry the c2/yawex authoring and reading patte
 
 ---
 
+## Capability structure for the wiki engine (reuse-surface-aligned)
+
+*Added by SHARD-WP-0013 T2 — a structural **layer over** the thematic catalog (UC IDs unchanged),
+mapping the 84 UCs onto a small **engine core** plus **typed, per-shard-activatable extensions**.
+This is the bridge from demand (UCs) to the engine's typed-extension model
+(`WikiEngineCoreArchitecture.md`, T5) and is aligned with the shard-wiki capability entries on the
+reuse surface (`capability.wiki.*`).*
+
+**Reading rule:** the engine is a **small always-on core**; everything else is a **typed extension
+a shard activates only if it needs it** (the activation mechanism itself reuses
+`capability.feature-control.evaluate`). "Default" = on/off for a standalone single-shard wiki.
+
+### Engine core (always on — the irreducible kernel)
+
+| Core unit | What it is | UCs | reuse-surface |
+|-----------|------------|-----|---------------|
+| **EC-1 Page lifecycle & content** | author / read / edit a Markdown page; delete is a history event | UC-08, UC-09 | `capability.wiki.page-model` |
+| **EC-2 Identity, naming & placement** | stable page identity ≠ placement; namespace/path | UC-22 (placement), page-model kernel | `capability.wiki.page-model` |
+| **EC-3 History & recoverability** | every write recoverable; history is the floor | UC-24 | `capability.wiki.coordination-journal` |
+| **EC-4 Links (wikilink + red-link)** | `[[Target]]` resolution; createable red-links | UC-23 | `capability.wiki.page-model` |
+| **EC-5 Storage via the adapter contract** | the engine *is* a canonical-mode shard behind §A | — | `capability.wiki.adapter-contract` (minimal profile) |
+
+EC-1…EC-5 are the Ward-Cunningham/c2 open-wiki minimum: write a page, link pages, never lose
+an edit. A shard can run with **only** the core.
+
+### Typed extensions (activate per shard)
+
+| Ext | Cluster | UCs | reuse-surface capability | Activatable | Default (standalone) |
+|-----|---------|-----|--------------------------|-------------|----------------------|
+| **X-OVERLAY** | overlay / lightweight-patch write path | UC-04, 26, 29 | `capability.wiki.overlay` | yes | on (no-op without remote/limited targets) |
+| **X-AUTHZ** | access-control ladder L0→L4 | UC-06 + the L-ladder | `capability.authorization.policy-evaluate` (reuse) | yes (tiered) | L0 (open) |
+| **X-VIEW** | derived views (RecentChanges, BackLinks, AllPages, SiteMap, Search) | UC-17–UC-21, UC-63 | (planned `capability.wiki.derived-views` — gap, T3) | yes | BackLinks/RecentChanges on; Search off |
+| **X-STRUCT** | structured / typed / computed page data + typed-graph | UC-34, 39, 58, 67, 73 | `capability.wiki.page-model` (typed) | yes | off |
+| **X-ADDR** | span addressing, transclusion, dimensional / query navigation | UC-32, 44–49, 51, 52, 74 | `capability.wiki.page-model` + query | yes (transclusion is core-lite) | transclusion on; dimensional/query off |
+| **X-COMP** | computational / executable content (literate, notebook, program-as-page, live) | UC-54, 55, 83, 84 | `capability.wiki.engine-typed-extensions` (computational) | yes (gated, trust/sandbox) | off |
+| **X-PROV** | rich provenance & page metadata | UC-25, 75 | `capability.wiki.page-model` (provenance) | yes (base provenance is core) | base on; rich off |
+| **X-COLLAB** | c2 collaboration / social patterns | UC-10–UC-16 | (UI/convention; partial gap, T3) | yes | varies (mostly UI-layer) |
+| **X-FED** | federation & union across shards | UC-01–07, 27, 28, 30–33, 56, 71, 72, 79 | `capability.wiki.shard-orchestration` + `…federation-models` | yes | off (single-shard engine) |
+| **X-ATT** | attach *foreign* backends as shards | UC-35–43, 50, 53, 57, 60–62, 64–66, 68–70, 76–82 | `capability.wiki.adapter-contract` | yes | off (orchestrator role, not the engine's own shard) |
+
+Note: X-FED and X-ATT are the **orchestrator** capabilities — for a *standalone* engine they are
+off; when shard-wiki orchestrates, the engine is simply one attached (canonical) shard among many.
+That is the engine↔orchestrator boundary made concrete (engine = a canonical-mode shard).
+
+### Conflict-mediation map (how the framework reconciles tensions into one whole)
+
+The collected UCs embed genuinely conflicting requirements. The framework mediates each with a
+**mechanism**, never a hard-coded policy — so one consistent featureset serves all:
+
+| Tension (conflicting UCs) | Mediation mechanism |
+|---------------------------|---------------------|
+| **Open vs governed** (UC-01 open edit ↔ UC-06 enterprise ACL) | the **L0→L4 authz ladder** (X-AUTHZ, additive); **history is the floor** at L0 — recoverability, not gatekeeping |
+| **Lossless vs lossy content** (UC-42 ↔ UC-59) | **translation spectrum + fidelity report** (TSD §A.6); native form stays canonical, loss is shown not hidden |
+| **Live vs snapshot** (UC-32 live transclusion ↔ UC-84/UC-3 cached) | the **live↔snapshot axis** + projection kind; degrade to a **marked** snapshot, never imply live |
+| **Canonical vs chorus** (UC-07 reconcile ↔ UC-27 coexist) | **conflict detection is core, resolution is a policy preset** (chorus / designated-canonical / …) |
+| **Eager vs lazy** (UC-03 projection ↔ UC-05 union) | **projection materialization** policy (lazy default; eager opt-in) |
+| **Single vs multi-writer** (concurrent edits) | **per-space append authority** on the coordination journal (total order, read-your-writes) |
+| **Integrated whole vs only-what-you-need** | the **typed-extension framework** + **per-shard activation** (reuse `feature-control`) — *the headline mediation*; extensions compose against typed contracts, so the featureset is one integrated whole yet selectively enabled |
+| **Minimal core vs feature-rich** | **small core (EC-1…EC-5)** + extensions; nothing beyond the c2 minimum is mandatory |
+
+This table is the seed of the engine's design rationale (T5): every conflict has a *mechanism*
+that lets a shard sit anywhere on the spectrum without forking the framework.
+
+---
+
 ## A. Information space, federation & coordination
 
 *Federation, union, overlay, projection, and the Git-backed coordination layer (INTENT + yawex/federation seeds).*

spec/WikiEngineCoreArchitecture.md

@@ -0,0 +1,269 @@
+# WikiEngineCoreArchitecture
+
+Status: **draft for review** · Date: 2026-06-15 · Deliverable of **SHARD-WP-0013 T5**
+
+The architecture of shard-wiki's **native reference wiki-engine**: a **headless, API-first**
+engine — a **small core** plus a **stringent typed-extension framework** — that addresses the
+whole use-case catalogue, mediates conflicting requirements into one integrated featureset, and
+lets each shard **activate only what it needs**. Authoritative as of the ratified INTENT
+amendment (2026-06-15, decision `84ffdb48`): the engine is **additive** and is shard-wiki's
+**reference first-party shard backend (a canonical-mode shard)** — not a replacement for other
+engines, not a UI.
+
+Relation to other specs (referenced, not restated):
+- `CoreArchitectureBlueprint.md` — the orchestrator/whole-system architecture. **The engine is
+  one shard behind §A; federation, union, projection, and cross-shard coordination are the
+  orchestrator's job, not the engine's.** That is what keeps the engine small.
+- `TechnicalSpecificationDocument.md §A` — the shard adapter contract the engine implements.
+- `FederationRequirements.md` — page resolution, overlay, link semantics (ADRs the engine reuses).
+- `UseCaseCatalog.md` "Capability structure" layer (T2) — the core-vs-extension map + the
+  conflict-mediation map this document realizes.
+- reuse surface (`capability.wiki.*`, plus consumed `feature-control` / `authorization`).
+
+---
+
+## 1. Thesis: a small page-store kernel; everything else is a typed extension
+
+> **The engine is a page-store kernel with a typed-extension runtime. Every capability beyond
+> the c2-minimum is a *typed extension* a shard activates only if it needs it — and a shard's
+> externally-visible capability profile is *computed from its active extension set*.**
+
+That single chain — **configuration (which extensions) → capability (what the shard can do) →
+conformance (verified)** — is the whole design. It mirrors the orchestrator's discipline
+(`CoreArchitectureBlueprint` §6.5: capability-as-data, verified, no per-backend code) and turns
+"integrated whole, yet activate only what you need" from a slogan into a mechanism.
+
+The engine stays small for a structural reason: it is **one shard**, not a federation layer.
+Union, projection, equivalence, cross-shard overlay-orchestration, and the federation models all
+live in shard-wiki's orchestrator (the blueprint). The engine implements `ShardAdapter` (§A) and
+nothing above it. So "wiki engine" here means *a really good single canonical shard with a
+typed-extension framework and a headless agent-first API* — not a re-implementation of shard-wiki.
+
+---
+
+## 2. Engine invariants
+
+| # | Invariant | Why |
+|---|-----------|-----|
+| E-1 | **One shard, not a federation layer.** The engine implements `ShardAdapter` (§A); union/projection/federation are the orchestrator's. | Keeps the engine small; no duplication of the blueprint. |
+| E-2 | **Small kernel.** The kernel is only: page store + history, the page model (reused), the extension runtime, the API. | Common case (a plain wiki) is trivial. |
+| E-3 | **Everything else is a typed extension.** No feature beyond the c2-minimum is baked into the kernel. | Integrated-whole-yet-selective; testable boundary. |
+| E-4 | **Per-shard activation.** A shard runs an *activation profile* (a set of extensions + config); unused features cost nothing. | "Activate only what you need." |
+| E-5 | **Capability profile is derived from active extensions.** The §A profile the engine declares is computed from its activation profile, then conformance-verified. | One source of truth; honest, verified capabilities. |
+| E-6 | **Headless & API-first.** The API is the only interface; no bundled UI/rendering (consumer concern, L6). | INTENT amendment; clean orchestrator/consumer split. |
+| E-7 | **Agent-first ergonomics.** The API is typed, introspectable, batchable, low-round-trip. | INTENT: optimized for efficient agent/automation access. |
+| E-8 | **Reuse over reinvent.** Page model, history/journal, activation, and authz are *consumed* (existing capabilities), not rebuilt. | Smallness; reuse-surface alignment. |
+| E-9 | **Extensions are typed & verified.** An extension declares its types/hooks/deps; activation is rejected if types conflict or deps are unmet (impossible profiles forbidden). | Stringency; mirrors §6.5 + conformance. |
+
+---
+
+## 3. The kernel (four concepts)
+
+The kernel is deliberately four things — nothing more is mandatory.
+
+1. **Page** — the backend-neutral page model (`capability.wiki.page-model`, reused as-is):
+   stable identity ≠ placement, layered provenance, page shapes. The kernel does **not** redefine
+   it; extensions may *register additional shapes/types* (§4).
+2. **Store + history** — a git-backed page store (the engine is the *git-IS-store* case from the
+   blueprint): a write is a commit; history is native and recoverable (E-3/I-10). Coordination
+   decisions reuse the event-sourced journal (`capability.wiki.coordination-journal`).
+3. **Extension runtime** — the typed-extension registry, hook dispatcher, type checker, and
+   activation engine (§4). *This is the core innovation; it is the only “framework” in the kernel.*
+4. **API** — the headless, typed, agent-first surface (§7). Kernel endpoints cover the c2-minimum
+   (page CRUD-as-history, links, history); extensions extend the surface through typed routes.
+
+The **c2-minimum** a kernel-only shard delivers (no extensions): write a page, link pages
+(`[[wikilink]]` + red-link), never lose an edit. That is a complete, useful headless wiki.
+
+---
+
+## 4. The typed-extension model (the framework)
+
+An **Extension** is a typed unit declaring a contract the runtime enforces:
+
+```
+Extension:
+  id            : reverse-domain id (e.g. ext.struct.typed-records)
+  provides      : capability ids it realizes (reuse-surface; e.g. capability.wiki.page-model[typed])
+  types         : page shapes / field schemas / content-types it introduces (typed, validated)
+  hooks         : kernel lifecycle bindings it implements (see below)
+  api           : typed routes it adds to the headless surface
+  depends_on    : other extensions / consumed capabilities required
+  conflicts_with: extensions it cannot co-activate with
+  config        : declared, schema-checked activation parameters
+```
+
+**Hooks (the kernel lifecycle the runtime dispatches):**
+`on_resolve` (name→page), `on_read`, `on_write` (validate/transform a draft), `on_link`
+(link/transclusion resolution), `on_history`, `on_query`, `on_render_request` (produce a derived
+representation for a consumer), `on_profile` (contribute capability-spectrum positions, E-5).
+Hooks are **typed** (typed inputs/outputs) and dispatched in a **declared, deterministic order**.
+
+**Typing & composition (stringency):**
+- At activation, the runtime builds the **dependency closure**, checks **type consistency** (no
+  two active extensions claim incompatible types for the same page shape/field; `conflicts_with`
+  honoured), and rejects an **impossible profile** — exactly the §6.5 implication-rule discipline,
+  applied to extensions. A rejected profile fails fast at boot, never silently.
+- Composition is **deterministic**: hook order is declared; conflicts are resolved by explicit
+  precedence or rejection, never by accident.
+- Extensions ship a **conformance check** (mirrors §6.6): an activated extension is exercised
+  against its declared types/hooks before the shard serves traffic — *typed contracts verified,
+  not trusted*.
+
+**Per-shard activation (reuse, not reinvent):**
+- A shard's **activation profile** = `{extension id → config}`. Activation/evaluation **reuses
+  `capability.feature-control.evaluate`** (helix_forge/feature-control) — shard-wiki does not
+  build a bespoke flagging system (T3 consumption).
+- **E-5 in action:** the engine's `on_profile` hooks fold the active extensions into the §A
+  **capability profile** the shard advertises to the orchestrator (e.g. activate
+  `ext.struct.typed-records` → the `structure` spectrum rises and `structured-payload` is
+  declared). The profile is then conformance-verified (§A.2). *Configuration → capability →
+  conformance is one chain.*
+
+---
+
+## 5. Featureset map: core vs extensions, and conflict mediation
+
+The engine realizes the T2 "Capability structure" layer (`UseCaseCatalog.md`). Mapping (the
+*page/content-level* clusters; **X-FED and X-ATT are orchestrator concerns, not engine
+extensions** — E-1):
+
+| Engine kernel (always on) | T2 | reuse-surface |
+|---------------------------|----|---------------|
+| Page lifecycle, identity/placement, history, links, store | EC-1…EC-5 | `capability.wiki.page-model`, `…coordination-journal`, `…adapter-contract` |
+
+| Built-in typed extension | T2 cluster | provides / consumes | default |
+|--------------------------|-----------|---------------------|---------|
+| `ext.overlay` | X-OVERLAY | `capability.wiki.overlay` | on (no-op locally) |
+| `ext.authz` (L0→L4 tiers) | X-AUTHZ | consumes `capability.authorization.policy-evaluate` | L0 |
+| `ext.views` (BackLinks/RecentChanges/…) | X-VIEW | `capability.wiki.derived-views` | BackLinks/RecentChanges on |
+| `ext.struct` (typed/computed/graph) | X-STRUCT | `capability.wiki.page-model[typed]` | off |
+| `ext.addr` (span addr / transclusion / query) | X-ADDR | `capability.wiki.page-model`+query | transclusion on |
+| `ext.compute` (literate/notebook/program/live) | X-COMP | `capability.wiki.engine-typed-extensions` | off (gated, sandbox) |
+| `ext.prov` (rich provenance/metadata) | X-PROV | `capability.wiki.page-model[provenance]` | base on |
+| `ext.collab` (c2 social patterns) | X-COLLAB | (UI/convention; mostly consumer) | off |
+
+**Conflict mediation (T2 map) realized by the framework** — every tension is a *mechanism*, not a
+baked-in choice, so one featureset serves all:
+
+| Tension | Realized by |
+|---------|-------------|
+| open vs governed | `ext.authz` tiers (additive); kernel history is the floor at L0 |
+| lossless vs lossy | a `translate` hook + fidelity report (consumes the proposed `capability.content.translation-fidelity`, G2) |
+| live vs snapshot | `ext.compute`/`ext.addr` mark liveness; degrade to snapshot (never imply live) |
+| canonical vs chorus | detection in kernel; resolution is a policy preset (orchestrator) |
+| integrated-whole vs only-what-you-need | **the activation profile** (E-4) + typed composition (§4) — the headline mediation |
+| minimal vs feature-rich | small kernel (§3) + extensions; nothing beyond c2 is mandatory |
+
+---
+
+## 6. The engine as a canonical-mode shard
+
+The engine exposes itself through an `EngineShardAdapter` implementing §A:
+
+- **Substrate** git-IS-store; **history** git-native; **write** = commit; `current_rev` = sha
+  (apply-under-drift works out of the box). It is the **most capable shard** shard-wiki can
+  attach — it dogfoods the contract.
+- Its **capability profile is computed from active extensions** (E-5) and **conformance-verified**
+  (§A.2) — so the orchestrator sees an honest profile, and federation ops degrade by the engine's
+  *actually-activated* capabilities.
+- The orchestrator attaches it like any shard; **federation/union/projection are not in the
+  engine** (E-1). A standalone deployment is "the engine as the sole canonical shard"; a
+  federated deployment is "the engine as one shard among many." Same engine, no re-architecture.
+
+This is the precise realization of the INTENT reconciliation: shard-wiki orchestrates; the engine
+is the first-party shard it can attach.
+
+---
+
+## 7. Headless API surface & agent ergonomics (E-6/E-7)
+
+API-first means the typed API is the product; there is no UI. Agent-first means it is designed
+for cheap, deterministic machine consumption:
+
+- **Typed resource API** over pages, links, history, spans — content-negotiated (raw Markdown,
+  the structured page model, or an extension-rendered representation via `on_render_request`).
+- **Capability/extension introspection** — an endpoint returns the shard's **active extensions,
+  their types, and the derived §A capability profile**, so an agent can discover *what this shard
+  can do* before acting (no trial-and-error). This is the agent-facing twin of E-5.
+- **Batch & query** — multi-page reads, link-graph and RecentChanges queries (via `ext.views`),
+  and `on_query` delegation — minimizing round-trips.
+- **Write via overlay** — edits go through the overlay path (FederationRequirements ADR-05), so
+  agent writes are safe (draft → apply-under-drift) and attributable.
+- **Deterministic & provenance-carrying** — every response carries the provenance envelope;
+  identical inputs yield identical outputs (no hidden state) — friendly to caching agents.
+
+---
+
+## 8. Implementation sketch (module layout)
+
+The engine lives under the shard-wiki package as a backend (it sits at L0/L1 — a shard behind the
+adapter; nothing in the orchestrator depends *up* on it):
+
+```
+src/shard_wiki/engine/
+  kernel.py        # page store + history (git-IS-store), lifecycle; reuses model/, provenance/, coordination/
+  extension.py     # Extension contract, registry, typed hook dispatcher, type checker
+  activation.py    # activation profile; reuses capability.feature-control.evaluate
+  profile.py       # derive the §A CapabilityProfile from active extensions (E-5) + conformance
+  api.py           # headless, typed, agent-first surface (+ extension introspection)
+  adapter.py       # EngineShardAdapter implements adapters/ ShardAdapter (canonical-mode shard)
+  extensions/      # built-ins: overlay/ authz/ views/ struct/ addr/ compute/ prov/ collab/
+```
+
+Dependency rule: `engine/` consumes `model/`, `provenance/`, `coordination/`, `adapters/`
+(contract), `policy/`; it is consumed *only* via its `EngineShardAdapter` (the orchestrator
+attaches it as a shard). No orchestrator-tier (`union/`, `projection/`) import.
+
+---
+
+## 9. Reuse (what the engine consumes vs registers)
+
+- **Consumes:** `capability.feature-control.evaluate` (activation), `capability.authorization.
+  policy-evaluate` (`ext.authz`), the proposed `capability.content.translation-fidelity` (G2,
+  lossy translation), and shard-wiki's own `capability.wiki.{page-model, coordination-journal,
+  adapter-contract, overlay, derived-views}`.
+- **Registers / realizes:** `capability.wiki.engine-typed-extensions` (this document is its
+  Discovery evidence — D2→D3 on ratification). The cross-cutting **typed-extension framework**
+  pattern is proposed back to the reuse surface as **G1** (`capability.platform.typed-extension-
+  framework`); this engine is its first instance.
+
+---
+
+## 10. Traceability
+
+- **INTENT** — realizes the 2026-06-15 amendment (decision `84ffdb48`): headless, API-first,
+  additive native engine = canonical-mode shard backend; honours all engine invariants and the
+  orchestrator boundary (E-1).
+- **Use cases** — the kernel/extension split *is* the T2 "Capability structure" layer
+  (`UseCaseCatalog.md`); every UC is either kernel (EC-1…EC-5) or a named extension; conflicts
+  use the T2 mediation map (§5). The engine must ultimately cover UC-01–UC-84 (per-shard subsets).
+- **Architecture** — consistent with `CoreArchitectureBlueprint` (engine = canonical-mode shard,
+  §6 contract, §7 page model, §8.1 journal) and `TechnicalSpecificationDocument §A` (the contract
+  it implements). `FederationRequirements` ADR-05/06 supply overlay + link semantics.
+- **Reuse surface** — §9; G1/G2 proposals from SHARD-WP-0013 T3.
+
+## 11. Decisions / deferred / open
+
+**Decided:** small page-store kernel + typed-extension runtime (E-2/E-3); engine is one shard,
+not a federation layer (E-1); capability profile derived from active extensions (E-5); headless,
+API-first, agent-first (E-6/E-7); activation reuses `feature-control` (E-8); extensions are
+typed + conformance-verified (E-9).
+
+**Deferred:** the concrete extension SDK/ABI and hook signatures; the API protocol (REST/GraphQL/
+MCP) — agent-first introspection is required, the wire format is an implementation spike; the
+built-in extensions' internal designs (each is a later workplan).
+
+**Open (tracked):** does `ext.compute` ever execute in-process or strictly delegate/snapshot
+(ties blueprint §8.5 + trust/sandbox); is the typed-extension framework promoted to the
+reuse-surface platform capability (G1) and then *consumed* here rather than engine-owned;
+introspection granularity vs. leaking internal structure to agents.
+
+## 12. Stability note
+
+The **thesis (§1)** and **invariants (§2)** — especially *engine-is-one-shard* (E-1),
+*small-kernel/everything-else-typed-extension* (E-2/E-3), and *capability-profile-derived-from-
+extensions* (E-5) — are load-bearing. Changing them (e.g. moving federation into the engine, or
+baking a feature into the kernel) is an architectural change in the sense of INTENT's Stability
+Note and should be rare and deliberate. The headless/API-first posture is fixed by the ratified
+INTENT amendment.

spec/adr/ADR-0001-engine-activation-via-feature-control.md

@@ -0,0 +1,79 @@
+# ADR-0001 — Engine extension activation via feature-control (OpenFeature)
+
+Status: **Accepted** · Date: 2026-06-15 · Deciders: tegwick · Source: SHARD-WP-0013 follow-up
+(feature-control assessment)
+
+> First repo-level ADR. (Note: `FederationRequirements.md` contains document-internal
+> "ADR-01…06" design notes — those are scoped to that spec; this `spec/adr/` series is the
+> repository's standalone architecture decision log, starting here.)
+
+## Context
+
+`WikiEngineCoreArchitecture.md` (SHARD-WP-0013 T5) defines the engine as a small kernel plus a
+**typed-extension framework** where each shard **activates only the extensions it needs**
+(invariants E-4 activation, E-8 reuse-not-reinvent). It needs a mechanism to decide, per shard
+(and per tenant/context), which extensions/features are active — without baking a bespoke flag
+system into the engine, and without breaking the **standalone, zero-external-dependency** L0
+posture shard-wiki guarantees.
+
+The helix_forge sibling **`feature-control`** (`capability.feature-control.evaluate`, registered
+at **D5 / A4 / C3 / R3**) provides exactly this: an **OpenFeature**-based feature-availability
+control plane with a working SDK (`feature_control_sdk`: `FeatureControlClient`, `Resolver`, a
+static `LocalProvider`), context-scoped evaluation (`tenant_id`/scope), explainable decisions,
+and graceful degradation when OpenFeature is absent. shard-wiki already proposed this as a T3
+*consumption* (reuse, don't rebuild).
+
+## Decision
+
+**Adopt `feature-control` (via the OpenFeature standard) as the engine's per-shard extension/
+feature activation mechanism** — *availability only* — with these constraints:
+
+1. **OpenFeature-shaped, provider-pluggable.** The engine evaluates activation through an
+   OpenFeature-style client. A static **`LocalProvider`** is the **standalone/L0 default**
+   (zero external dependency); a `feature-control`/remote provider is plugged in for governed
+   deployments. This mirrors shard-wiki's existing **identity-provider ladder** (null/local
+   default → external when present).
+2. **Availability ≠ authorization.** feature-control decides *which extensions are active*,
+   never *who may read/write*. Authorization stays in core (X-AUTHZ / `authorization.policy-
+   evaluate`). The two are composed but never conflated. (feature-control's own INTENT requires
+   this.)
+3. **Engine layer, not the orchestrator foundation.** Integration lives in
+   `engine/activation.py`; the current `src/shard_wiki/` core stays dependency-free. OpenFeature/
+   feature-control is an optional extra, kept out of the standalone path by the `LocalProvider`.
+4. **Thin slice only.** Consume `feature-control.evaluate` (mature, A4). Do **not** take a
+   dependency on the heavier control-plane governance / `rollout` / `visibility` (A2) until a
+   concrete need appears.
+
+Activation keys = extension ids; evaluation context = `{tenant_id: root-entity, shard_id, …}`;
+the resulting active-extension set then **derives** the shard's §A capability profile (E-5).
+
+## Consequences
+
+**Positive**
+- No bespoke flag system; reuses a mature (D5/A4) capability — reuse-surface aligned.
+- Standalone stays zero-dep (LocalProvider); governed deployments get real runtime control,
+  multi-tenant scoping, and **explainable** decisions that feed the engine's agent-introspection
+  API (E-7: "why is extension X off for this shard?").
+- "Activate only what you need" + compute control become first-class and reversible at runtime.
+- Clean layering: availability (feature-control) vs authorization (core) vs identity (provider).
+
+**Negative / risks (mitigated by the constraints)**
+- An optional OpenFeature dependency at the engine layer (mitigated: out of the standalone path).
+- Coupling to an external control plane in governed mode (mitigated: provider-pluggable, degrade
+  to LocalProvider).
+- Temptation to route authz through it (mitigated: constraint 2, hard boundary).
+
+## Alternatives considered
+
+- **Bespoke per-shard flag/config in the engine** — rejected: reinvents feature-control, no
+  standard, no multi-tenant/explainability, violates reuse-not-reinvent (E-8).
+- **No activation (all extensions always on)** — rejected: defeats "small core + activate only
+  what you need" (E-2/E-4) and the compute-control goal.
+- **Build on the heavier feature-control control-plane now** — deferred: over-scoping a single
+  engine's activation; revisit if rollout/governance needs emerge.
+
+## Related
+
+`WikiEngineCoreArchitecture.md` (E-4/E-8, §4 activation), `UseCaseCatalog.md` capability-structure
+layer (X-AUTHZ vs activation), `history/260615-reuse-surface-contributions.md` (T3 consumption),
+reuse-surface `capability.feature-control.evaluate`, INTENT amendment decision `84ffdb48`.

spec/adr/README.md

@@ -0,0 +1,11 @@
+# spec/adr/ — Architecture Decision Records
+
+Repository-level ADRs: one decision per file, `ADR-NNNN-<slug>.md`, status
+**Proposed / Accepted / Superseded**. Each records Context · Decision · Consequences ·
+Alternatives. These are the standalone, numbered decision log; design-note "ADRs" embedded
+inside a spec (e.g. `FederationRequirements.md` ADR-01…06) are scoped to that document and are
+not part of this series.
+
+| ADR | Status | Subject |
+|-----|--------|---------|
+| [ADR-0001](ADR-0001-engine-activation-via-feature-control.md) | Accepted | Engine extension activation via feature-control (OpenFeature), availability-only, LocalProvider standalone default |

src/shard_wiki/__init__.py

@@ -1,10 +1,16 @@
 """shard-wiki — Git-based Markdown wiki orchestrator and federation layer.
 
-See INTENT.md for the authoritative specification of scope and boundaries.
-This package orchestrates wiki-shaped content across heterogeneous *shards*;
-it is not itself a wiki engine.
+See INTENT.md for the authoritative specification of scope and boundaries, and
+spec/CoreArchitectureBlueprint.md for the architecture. This package orchestrates
+wiki-shaped content across heterogeneous *shards*; it is not itself a wiki engine.
+
+Foundation slice (SHARD-WP-0007): attach folder shard(s) to an
+:class:`~shard_wiki.space.InformationSpace`, resolve a name through the union, and
+read a page with layered provenance (chorus on ambiguity).
 """
 
+from shard_wiki.space import InformationSpace
+
 __version__ = "0.0.0"
 
-__all__ = ["__version__"]
+__all__ = ["__version__", "InformationSpace"]

src/shard_wiki/adapters/__init__.py

@@ -0,0 +1,25 @@
+"""adapters/ — the shard adapter contract (bottom waist) and concrete adapters."""
+
+from shard_wiki.adapters.conformance import (
+    Check,
+    ConformanceError,
+    ConformanceReport,
+    assert_conformant,
+    run_conformance,
+)
+from shard_wiki.adapters.contract import CONTRACT_VERSION, ShardAdapter
+from shard_wiki.adapters.folder import FolderAdapter
+from shard_wiki.adapters.git import GitShardAdapter, PageRevision
+
+__all__ = [
+    "ShardAdapter",
+    "FolderAdapter",
+    "GitShardAdapter",
+    "PageRevision",
+    "CONTRACT_VERSION",
+    "Check",
+    "ConformanceReport",
+    "ConformanceError",
+    "run_conformance",
+    "assert_conformant",
+]

src/shard_wiki/adapters/conformance.py

@@ -0,0 +1,142 @@
+"""Adapter conformance — profiles are verified, not self-asserted (TSD §A.2, blueprint §6.6).
+
+Capability-as-data (I-3) is only sound if a binding's *declared* profile matches its *observed*
+behaviour. This battery exercises a binding and reports, check by check, whether claim == reality;
+``assert_conformant`` gates registration. A lying/buggy profile fails here instead of silently
+poisoning degradation decisions downstream.
+
+This slice verifies the read path + honest absence of unclaimed verbs. Positive probes for
+claimed write/diff/merge are deferred (they mutate) to a later workplan.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+from shard_wiki.adapters.contract import ShardAdapter
+from shard_wiki.model import NotSupported, Verb
+
+__all__ = ["Check", "ConformanceReport", "ConformanceError", "run_conformance", "assert_conformant"]
+
+# Optional verbs whose *absence* must be honest (calling an unclaimed one raises NotSupported).
+_HONEST_ABSENCE_VERBS = (Verb.WRITE, Verb.DIFF, Verb.NOTIFY)
+_PROBE = {
+    Verb.WRITE: lambda a: a.write("__probe__", ""),
+    Verb.DIFF: lambda a: a.diff("__probe__", "__probe2__"),
+    Verb.NOTIFY: lambda a: a.notify(),
+}
+
+
+@dataclass(frozen=True, slots=True)
+class Check:
+    name: str
+    ok: bool
+    detail: str = ""
+
+
+@dataclass(frozen=True, slots=True)
+class ConformanceReport:
+    adapter: str
+    checks: tuple[Check, ...]
+
+    @property
+    def ok(self) -> bool:
+        return all(c.ok for c in self.checks)
+
+    @property
+    def failures(self) -> tuple[Check, ...]:
+        return tuple(c for c in self.checks if not c.ok)
+
+    def diff(self) -> str:
+        return "; ".join(f"{c.name}: {c.detail}" for c in self.failures) or "conformant"
+
+
+class ConformanceError(Exception):
+    def __init__(self, report: ConformanceReport) -> None:
+        super().__init__(f"{report.adapter} not conformant — {report.diff()}")
+        self.report = report
+
+
+def _safe(fn, name: str, ok_detail: str = "") -> Check:
+    try:
+        return fn()
+    except Exception as exc:  # noqa: BLE001 — a check must never crash the battery
+        return Check(name, False, f"unexpected error: {exc!r}")
+
+
+def run_conformance(adapter: ShardAdapter) -> ConformanceReport:
+    checks: list[Check] = []
+    profile = None
+
+    def _profile_validates() -> Check:
+        nonlocal profile
+        profile = adapter.profile()
+        profile.validate()
+        return Check("profile-validates", True)
+
+    checks.append(_safe(_profile_validates, "profile-validates"))
+    if profile is None:  # profile() or validate() failed; can't probe further meaningfully
+        return ConformanceReport(type(adapter).__name__, tuple(checks))
+
+    # READ is the capability floor.
+    checks.append(Check("supports-read", profile.supports(Verb.READ),
+                        "" if profile.supports(Verb.READ) else "READ not declared"))
+
+    # READ round-trips: a declared-readable shard must actually read its own keys.
+    def _read_round_trips() -> Check:
+        keys = list(adapter.keys())
+        if not keys:
+            return Check("read-round-trips", True, "empty shard")
+        page = adapter.read(keys[0])
+        if page.identity.shard != adapter.shard_id:
+            return Check("read-round-trips", False,
+                         f"page shard {page.identity.shard!r} != {adapter.shard_id!r}")
+        if not isinstance(page.body, str):
+            return Check("read-round-trips", False, "body is not text")
+        return Check("read-round-trips", True)
+
+    if profile.supports(Verb.READ):
+        checks.append(_safe(_read_round_trips, "read-round-trips"))
+
+    # WRITE positive probe: a claimed-writable shard must actually round-trip a write. The probe
+    # is content-preserving (rewrite an existing page with its own body) so it is non-destructive.
+    def _write_round_trips() -> Check:
+        keys = list(adapter.keys())
+        if not keys:
+            return Check("write-round-trips", True, "empty shard")
+        k = keys[0]
+        original = adapter.read(k).body
+        adapter.write(k, original)
+        if adapter.read(k).body != original:
+            return Check("write-round-trips", False, "rewrite did not preserve body")
+        return Check("write-round-trips", True)
+
+    if profile.supports(Verb.WRITE):
+        checks.append(_safe(_write_round_trips, "write-round-trips"))
+
+    # Honest absence: an *unclaimed* optional verb must raise NotSupported when invoked.
+    for verb in _HONEST_ABSENCE_VERBS:
+        if profile.supports(verb):
+            continue  # claimed → positive probe deferred (would mutate)
+        name = f"honest-absence:{verb.value}"
+
+        def _probe(v=verb, n=name) -> Check:
+            try:
+                _PROBE[v](adapter)
+            except NotSupported:
+                return Check(n, True)
+            except Exception as exc:  # noqa: BLE001
+                return Check(n, False, f"raised {type(exc).__name__}, expected NotSupported")
+            return Check(n, False, "did not raise NotSupported though verb is unclaimed")
+
+        checks.append(_probe())
+
+    return ConformanceReport(type(adapter).__name__, tuple(checks))
+
+
+def assert_conformant(adapter: ShardAdapter) -> ConformanceReport:
+    """Run the battery; raise :class:`ConformanceError` if any check fails. Returns the report."""
+    report = run_conformance(adapter)
+    if not report.ok:
+        raise ConformanceError(report)
+    return report

src/shard_wiki/adapters/contract.py

@@ -0,0 +1,52 @@
+"""The shard adapter contract — the bottom narrow waist (CoreArchitectureBlueprint §6, TSD §A).
+
+A backend participates by implementing :class:`ShardAdapter`. ``shard_id``, ``profile`` and
+``read`` are mandatory; everything else is an optional capability that defaults to raising
+:class:`~shard_wiki.model.NotSupported` — so a limited backend is honest about what it can't do
+(graceful degradation, I-8) and core never assumes a capability it wasn't given (capability-as-
+data, I-3). Declared profiles are verified by the conformance suite (T4), never taken on trust.
+"""
+
+from __future__ import annotations
+
+import abc
+from collections.abc import Iterable
+
+from shard_wiki.model import CapabilityProfile, NotSupported, Page
+
+__all__ = ["ShardAdapter", "CONTRACT_VERSION"]
+
+CONTRACT_VERSION = "0.1"
+
+
+class ShardAdapter(abc.ABC):
+    """Versioned interface a backend implements to attach as a shard."""
+
+    contract_version: str = CONTRACT_VERSION
+
+    @property
+    @abc.abstractmethod
+    def shard_id(self) -> str:
+        """Stable id scoping every Identity this shard mints."""
+
+    @abc.abstractmethod
+    def profile(self) -> CapabilityProfile:
+        """The (to-be-verified) capability profile of this binding."""
+
+    @abc.abstractmethod
+    def keys(self) -> Iterable[str]:
+        """The stable page keys this shard offers (the handle half of Identity)."""
+
+    @abc.abstractmethod
+    def read(self, key: str) -> Page:
+        """Read one page by its stable key. Raises ``KeyError`` if absent."""
+
+    # --- optional capability verbs: honest NotSupported by default ---
+    def write(self, key: str, body: str) -> Page:  # noqa: ARG002
+        raise NotSupported(f"{type(self).__name__} does not support write")
+
+    def diff(self, key: str, other: str) -> str:  # noqa: ARG002
+        raise NotSupported(f"{type(self).__name__} does not support diff")
+
+    def notify(self):
+        raise NotSupported(f"{type(self).__name__} does not support notify")

src/shard_wiki/adapters/folder.py

@@ -0,0 +1,111 @@
+"""FolderAdapter — a read-only file-store shard over a directory of Markdown.
+
+The home-case substrate: a plain folder of ``.md`` files. The relative path (sans extension,
+``/``-separated) is the stable page **key**; the file is the page **body**; mtime gives a
+freshness stamp. Read-only in this slice (overlay/write-through come later); declared profile
+reflects exactly that (read-only, file-store, path addressing, no native history/query).
+"""
+
+from __future__ import annotations
+
+from collections.abc import Iterable
+from datetime import datetime, timezone
+from pathlib import Path
+
+from shard_wiki.adapters.contract import ShardAdapter
+from shard_wiki.model import (
+    AccessGrant,
+    Addressing,
+    AttachmentMode,
+    CapabilityProfile,
+    ContentOpacity,
+    History,
+    Identity,
+    MergeModel,
+    NativeQuery,
+    NotSupported,
+    OperationalEnvelope,
+    Page,
+    Placement,
+    Substrate,
+    Translation,
+    Verb,
+    WriteGranularity,
+)
+from shard_wiki.provenance import Liveness, ProvenanceEnvelope, Staleness
+
+__all__ = ["FolderAdapter"]
+
+
+class FolderAdapter(ShardAdapter):
+    def __init__(self, shard_id: str, root: str | Path, writable: bool = False) -> None:
+        self._shard_id = shard_id
+        self._root = Path(root)
+        self._writable = writable
+
+    @property
+    def shard_id(self) -> str:
+        return self._shard_id
+
+    def profile(self) -> CapabilityProfile:
+        verbs = {Verb.READ, Verb.WRITE} if self._writable else {Verb.READ}
+        granularity = WriteGranularity.PER_PAGE if self._writable else WriteGranularity.NONE
+        return CapabilityProfile(
+            substrate=Substrate.FILES,
+            attachment_mode=AttachmentMode.FILE_STORE,
+            write_granularity=granularity,
+            content_opacity=ContentOpacity.TRANSPARENT,
+            operational_envelope=OperationalEnvelope.LOCAL_UNBOUNDED,
+            access_grant=AccessGrant.OPEN,
+            liveness=Liveness.STATIC,
+            history=History.NONE,
+            merge_model=MergeModel.NONE,
+            addressing=Addressing.PATH,
+            native_query=NativeQuery.NONE,
+            translation=Translation.NATIVE,
+            supported_verbs=frozenset(verbs),
+        ).validate()
+
+    def _path_for(self, key: str) -> Path:
+        return self._root / f"{key}.md"
+
+    def current_rev(self, key: str) -> str | None:
+        """The shard's current revision token for ``key`` (mtime iso), or ``None`` if absent.
+        Used for apply-under-drift comparison (blueprint §8.6)."""
+        path = self._path_for(key)
+        if not path.is_file():
+            return None
+        return datetime.fromtimestamp(path.stat().st_mtime, tz=timezone.utc).isoformat()
+
+    def write(self, key: str, body: str) -> Page:
+        if not self._writable:
+            raise NotSupported(f"{type(self).__name__} is read-only")
+        path = self._path_for(key)
+        path.parent.mkdir(parents=True, exist_ok=True)
+        path.write_text(body, encoding="utf-8")
+        return self.read(key)
+
+    def keys(self) -> Iterable[str]:
+        for p in sorted(self._root.rglob("*.md")):
+            yield p.relative_to(self._root).with_suffix("").as_posix()
+
+    def read(self, key: str) -> Page:
+        path = self._path_for(key)
+        if not path.is_file():
+            raise KeyError(key)
+        body = path.read_text(encoding="utf-8")
+        mtime = datetime.fromtimestamp(path.stat().st_mtime, tz=timezone.utc)
+        envelope = ProvenanceEnvelope(
+            source_shard=self._shard_id,
+            liveness=Liveness.STATIC,
+            staleness=Staleness.FRESH,
+            source_rev=mtime.isoformat(),
+            observed_at=datetime.now(tz=timezone.utc),
+        )
+        rel = path.relative_to(self._root).as_posix()
+        return Page(
+            identity=Identity(self._shard_id, key),
+            body=body,
+            envelope=envelope,
+            placements=(Placement(self._shard_id, rel),),
+        )

src/shard_wiki/adapters/git.py

@@ -0,0 +1,180 @@
+"""GitShardAdapter — a second substrate: git-as-store (SHARD-WP-0012; TSD §A.3 git-IS-store).
+
+The home case where **git is the store *and* the journal**. Tracked ``*.md`` paths are the page
+keys; the working-tree file is the body; a page's ``source_rev`` is the **commit sha of the last
+commit touching its path** (per-path, so an edit to one page never drifts another). The declared
+profile is *git-IS-store ⟹ substrate=git ∧ history=git-native* — the implication rule the
+capability model enforces (§6.5), validated at registration like any other binding.
+
+This adapter adds **no core changes**: it implements the same :class:`ShardAdapter` contract the
+folder adapter does, proving "write an adapter + declare a verified profile" is the whole cost of a
+new substrate (capability-as-data, I-3). Built on the ``git`` CLI via subprocess — zero new deps.
+"""
+
+from __future__ import annotations
+
+import os
+import subprocess
+from collections.abc import Iterable
+from dataclasses import dataclass
+from pathlib import Path
+
+from shard_wiki.adapters.contract import ShardAdapter
+from shard_wiki.model import (
+    AccessGrant,
+    Addressing,
+    AttachmentMode,
+    CapabilityProfile,
+    ContentOpacity,
+    History,
+    Identity,
+    MergeModel,
+    NativeQuery,
+    NotSupported,
+    OperationalEnvelope,
+    Page,
+    Placement,
+    Substrate,
+    Translation,
+    Verb,
+    WriteGranularity,
+)
+from shard_wiki.provenance import Liveness, ProvenanceEnvelope, Staleness
+
+__all__ = ["GitShardAdapter", "PageRevision"]
+
+
+@dataclass(frozen=True, slots=True)
+class PageRevision:
+    """One adopted git-native revision of a page: the commit sha and its subject line."""
+
+    sha: str
+    message: str
+
+_GIT_IDENTITY = {
+    "GIT_AUTHOR_NAME": "shard-wiki",
+    "GIT_AUTHOR_EMAIL": "shard@shard-wiki",
+    "GIT_COMMITTER_NAME": "shard-wiki",
+    "GIT_COMMITTER_EMAIL": "shard@shard-wiki",
+}
+
+
+class GitShardAdapter(ShardAdapter):
+    """A shard whose store is a git repo: keys are tracked ``*.md`` paths, revs are commit shas."""
+
+    def __init__(self, shard_id: str, repo_path: str | Path, writable: bool = False) -> None:
+        self._shard_id = shard_id
+        self._repo = Path(repo_path)
+        self._writable = writable
+        self._repo.mkdir(parents=True, exist_ok=True)
+        if not (self._repo / ".git").exists():
+            self._git("init", "--quiet")
+
+    @property
+    def shard_id(self) -> str:
+        return self._shard_id
+
+    def profile(self) -> CapabilityProfile:
+        # VERSION is always available — a git-IS-store has git-native history to adopt (§A.5),
+        # read-only or not. WRITE (= commit, PER_PAGE) is added only in writable mode.
+        verbs = {Verb.READ, Verb.VERSION}
+        granularity = WriteGranularity.NONE
+        if self._writable:
+            verbs |= {Verb.WRITE}
+            granularity = WriteGranularity.PER_PAGE
+        return CapabilityProfile(
+            substrate=Substrate.GIT,
+            attachment_mode=AttachmentMode.GIT_IS_STORE,
+            write_granularity=granularity,
+            content_opacity=ContentOpacity.TRANSPARENT,
+            operational_envelope=OperationalEnvelope.LOCAL_UNBOUNDED,
+            access_grant=AccessGrant.OPEN,
+            liveness=Liveness.STATIC,
+            history=History.GIT_NATIVE,  # git-is-store ⟹ git-native (§6.5)
+            merge_model=MergeModel.GIT_TEXT,
+            addressing=Addressing.PATH,
+            native_query=NativeQuery.NONE,
+            translation=Translation.NATIVE,
+            supported_verbs=frozenset(verbs),
+        ).validate()
+
+    def write(self, key: str, body: str) -> Page:
+        """Write = **commit**: stage the file and commit it (skip a no-op so no empty commit),
+        returning the page at the new sha. Drift detection rides on ``current_rev`` = that sha."""
+        if not self._writable:
+            raise NotSupported(f"{type(self).__name__} is read-only")
+        rel = f"{key}.md"
+        path = self._path_for(key)
+        path.parent.mkdir(parents=True, exist_ok=True)
+        path.write_text(body, encoding="utf-8")
+        self._git("add", "--", rel)
+        if self._run("diff", "--cached", "--quiet").returncode != 0:  # staged changes present
+            self._git("commit", "-m", f"write {rel}", env=_GIT_IDENTITY)
+        return self.read(key)
+
+    def keys(self) -> Iterable[str]:
+        out = self._git("ls-files", "*.md").decode()
+        for line in out.splitlines():
+            yield line[: -len(".md")] if line.endswith(".md") else line
+
+    def read(self, key: str) -> Page:
+        path = self._path_for(key)
+        if not path.is_file():
+            raise KeyError(key)
+        rev = self.current_rev(key)
+        return Page(
+            identity=Identity(self._shard_id, key),
+            body=path.read_text(encoding="utf-8"),
+            envelope=ProvenanceEnvelope(
+                source_shard=self._shard_id,
+                liveness=Liveness.STATIC,
+                staleness=Staleness.FRESH,
+                source_rev=rev,
+                lineage="git-native",
+            ),
+            placements=(Placement(self._shard_id, f"{key}.md"),),
+        )
+
+    def current_rev(self, key: str) -> str | None:
+        """The sha of the last commit touching ``key``'s path (per-path drift token), or None."""
+        rel = f"{key}.md"
+        if not self._path_for(key).is_file():
+            return None
+        sha = self._git("log", "-1", "--format=%H", "--", rel).decode().strip()
+        return sha or None
+
+    def history(self, key: str) -> tuple[PageRevision, ...]:
+        """Adopt git-native history (§A.5): the commit list for ``key``'s path, newest-first.
+
+        VERSION-gated; raises ``KeyError`` for an unknown page. Each revision is a commit sha +
+        subject — the native log surfaced through the contract, not re-implemented.
+        """
+        if not self.profile().supports(Verb.VERSION):
+            raise NotSupported(f"{type(self).__name__} does not support version")
+        if not self._path_for(key).is_file():
+            raise KeyError(key)
+        out = self._git("log", "--format=%H%x00%s", "--", f"{key}.md").decode()
+        revisions = []
+        for line in out.splitlines():
+            sha, _, message = line.partition("\x00")
+            revisions.append(PageRevision(sha=sha, message=message))
+        return tuple(revisions)
+
+    # -- git plumbing --------------------------------------------------------
+
+    def _path_for(self, key: str) -> Path:
+        return self._repo / f"{key}.md"
+
+    def _git(self, *args: str, stdin: bytes | None = None, env: dict | None = None) -> bytes:
+        return self._run(*args, stdin=stdin, env=env, check=True).stdout
+
+    def _run(
+        self, *args: str, stdin: bytes | None = None, env: dict | None = None, check: bool = False
+    ) -> subprocess.CompletedProcess:
+        return subprocess.run(
+            ["git", "-C", str(self._repo), *args],
+            input=stdin,
+            capture_output=True,
+            env={**os.environ, **(env or {})},
+            check=check,
+        )

src/shard_wiki/coordination/__init__.py

@@ -0,0 +1,58 @@
+"""coordination/ — the event-sourced decision log (L3, coordination-canonical state)."""
+
+from shard_wiki.coordination.decision_log import (
+    CoordinationState,
+    DecisionEvent,
+    DecisionLog,
+    EventStore,
+    EventType,
+    InMemoryEventStore,
+    deserialize_event,
+    serialize_event,
+)
+from shard_wiki.coordination.append_authority import (
+    AppendAuthority,
+    Lease,
+    LeaseHeld,
+    LeaseRegistry,
+)
+from shard_wiki.coordination.git_event_store import GitEventStore
+from shard_wiki.coordination.migration import (
+    export_jsonl,
+    import_jsonl,
+    import_log,
+    migrate_space,
+)
+from shard_wiki.coordination.overlay import (
+    ApplyResult,
+    ApplyStatus,
+    Overlay,
+    OverlayEngine,
+)
+from shard_wiki.coordination.patch import Patch, render_patch
+
+__all__ = [
+    "DecisionLog",
+    "DecisionEvent",
+    "EventType",
+    "CoordinationState",
+    "EventStore",
+    "InMemoryEventStore",
+    "GitEventStore",
+    "Lease",
+    "LeaseHeld",
+    "LeaseRegistry",
+    "AppendAuthority",
+    "import_log",
+    "migrate_space",
+    "export_jsonl",
+    "import_jsonl",
+    "serialize_event",
+    "deserialize_event",
+    "Overlay",
+    "OverlayEngine",
+    "ApplyStatus",
+    "ApplyResult",
+    "Patch",
+    "render_patch",
+]

src/shard_wiki/coordination/append_authority.py

@@ -0,0 +1,158 @@
+"""Per-space append authority — the single-writer lease over the log (SHARD-WP-0009 T2).
+
+The log is a *total order per space* (§8.6). :class:`~shard_wiki.coordination.git_event_store`
+makes a fork physically impossible via compare-and-swap; this layer adds the **policy** that gives
+the order a single designated writer: a **per-space lease**. At most one node holds a space's lease
+at a time; only the holder writes to the store. A non-holder does not write — it **forwards** its
+append intent to the current holder, so intents from anywhere still land in one serialized stream.
+
+The lease is **time-bounded and re-grantable** (HA): if a holder dies, its lease expires and a new
+node may take it, resuming appends from the log head (``seq`` stays contiguous across the hand-off).
+A node holding a *stale* lease (already re-granted elsewhere) cannot write either — it discovers it
+is no longer the holder and forwards instead, so a partitioned ex-holder can never fork the log.
+
+Mechanism over policy (CLAUDE.md): this provides the leasing *primitive*; who acquires when, and
+the TTL, are the caller's policy. Single-coordinator only — distributed multi-node leasing and log
+sharding are explicit non-goals of this workplan.
+"""
+
+from __future__ import annotations
+
+import uuid
+from collections.abc import Callable, Mapping
+from dataclasses import dataclass
+from datetime import datetime, timedelta, timezone
+from typing import Any
+
+from shard_wiki.coordination.decision_log import DecisionEvent, EventStore, EventType
+
+__all__ = ["Lease", "LeaseHeld", "LeaseRegistry", "AppendAuthority"]
+
+
+def _utcnow() -> datetime:
+    return datetime.now(tz=timezone.utc)
+
+
+@dataclass(frozen=True, slots=True)
+class Lease:
+    """A time-bounded grant of single-writer authority over one space."""
+
+    space: str
+    holder: str
+    token: str
+    expires_at: datetime
+
+    def valid_at(self, now: datetime) -> bool:
+        return now < self.expires_at
+
+
+class LeaseHeld(Exception):
+    """Raised when a space's lease is validly held by a different node."""
+
+    def __init__(self, lease: Lease) -> None:
+        super().__init__(
+            f"space {lease.space!r} leased to {lease.holder!r} until {lease.expires_at}"
+        )
+        self.lease = lease
+
+
+class LeaseRegistry:
+    """The single coordinator's grant table: at most one *valid* lease per space.
+
+    A lease that has expired is freely re-grantable to any node (the HA replacement path); a still
+    valid lease is exclusive to its holder (renewable by that holder). The registry also routes
+    forwarded append intents to the current holder node.
+    """
+
+    def __init__(self, clock: Callable[[], datetime] = _utcnow) -> None:
+        self._clock = clock
+        self._leases: dict[str, Lease] = {}
+        self._nodes: dict[str, AppendAuthority] = {}
+
+    def register(self, node: AppendAuthority) -> None:
+        self._nodes[node.node_id] = node
+
+    def grant(self, space: str, holder: str, ttl_seconds: float) -> Lease:
+        """Grant/renew the lease for ``space`` to ``holder``; raise :class:`LeaseHeld` if another
+        node still holds it validly. An expired lease is re-grantable to anyone."""
+        now = self._clock()
+        current = self._leases.get(space)
+        if current is not None and current.valid_at(now) and current.holder != holder:
+            raise LeaseHeld(current)
+        lease = Lease(
+            space=space,
+            holder=holder,
+            token=uuid.uuid4().hex,
+            expires_at=now + timedelta(seconds=ttl_seconds),
+        )
+        self._leases[space] = lease
+        return lease
+
+    def current(self, space: str) -> Lease | None:
+        """The lease for ``space`` if one is currently valid, else None (expired/absent)."""
+        lease = self._leases.get(space)
+        return lease if lease is not None and lease.valid_at(self._clock()) else None
+
+    def holder_node(self, space: str) -> AppendAuthority | None:
+        lease = self.current(space)
+        return self._nodes.get(lease.holder) if lease is not None else None
+
+
+class AppendAuthority:
+    """A coordinator node that appends to the shared log only when it holds the space's lease.
+
+    Nodes share one :class:`EventStore` and one :class:`LeaseRegistry`. ``append`` routes itself:
+    the holder writes; a non-holder forwards to whoever holds the lease (acquiring it first if the
+    space is currently unleased). The append API mirrors :class:`EventStore` so the authority is a
+    drop-in single-writer guard.
+    """
+
+    def __init__(
+        self,
+        node_id: str,
+        store: EventStore,
+        registry: LeaseRegistry,
+        ttl_seconds: float = 30.0,
+    ) -> None:
+        self.node_id = node_id
+        self._store = store
+        self._registry = registry
+        self._ttl = ttl_seconds
+        registry.register(self)
+
+    def acquire(self, space: str) -> Lease:
+        """Take (or renew) the lease for ``space``. Raises :class:`LeaseHeld` if another node holds
+        it validly."""
+        return self._registry.grant(space, self.node_id, self._ttl)
+
+    def holds(self, space: str) -> bool:
+        lease = self._registry.current(space)
+        return lease is not None and lease.holder == self.node_id
+
+    def append(
+        self,
+        space: str,
+        type: EventType,
+        payload: Mapping[str, Any],
+        actor: str | None = None,
+    ) -> DecisionEvent:
+        """Append via the single authority. If we hold the lease, write; otherwise forward to the
+        holder. If the space is unleased, acquire it first. A node with a *stale* lease forwards
+        (it is not the current holder) rather than writing — so it cannot fork the log."""
+        holder_node = self._registry.holder_node(space)
+        if holder_node is None:
+            self.acquire(space)  # unleased: take authority, then write below
+            holder_node = self
+        if holder_node is self:
+            return self._store.append(space, type, payload, actor=actor)
+        return holder_node._write(space, type, payload, actor=actor)
+
+    def _write(
+        self,
+        space: str,
+        type: EventType,
+        payload: Mapping[str, Any],
+        actor: str | None,
+    ) -> DecisionEvent:
+        """Apply a forwarded intent. Called only on the lease holder by a forwarding peer."""
+        return self._store.append(space, type, payload, actor=actor)

src/shard_wiki/coordination/decision_log.py

@@ -0,0 +1,208 @@
+"""The event-sourced coordination decision log — the keystone (CoreArchitectureBlueprint §8.1).
+
+Coordination-canonical state (overlays, equivalence bindings, aliases, merges, forks) is an
+**append-only decision log**, not a mutable file; the queryable *current* state is a **derived
+fold** of the log (tier-3 disposable). The log is **totally ordered per space** via a single
+**append authority**. That total order is what gives read-your-writes across readers (§8.6).
+
+Storage lives behind :class:`EventStore`: :class:`InMemoryEventStore` is the default test double
+(an in-process counter); :class:`~shard_wiki.coordination.git_event_store.GitEventStore` is the
+git-addressable backend (SHARD-WP-0009). The :class:`DecisionLog` API and the :meth:`fold` are
+identical across backends — only storage + the concurrency model differ.
+
+`derived = f(canonical)`: :class:`CoordinationState` is always reproducible by replaying the log.
+"""
+
+from __future__ import annotations
+
+import json
+from collections.abc import Mapping
+from dataclasses import dataclass, field
+from datetime import datetime, timezone
+from enum import Enum
+from types import MappingProxyType
+from typing import Any, Protocol, runtime_checkable
+
+__all__ = [
+    "EventType",
+    "DecisionEvent",
+    "CoordinationState",
+    "EventStore",
+    "InMemoryEventStore",
+    "DecisionLog",
+    "serialize_event",
+    "deserialize_event",
+]
+
+
+class EventType(Enum):
+    OVERLAY_CREATED = "overlay-created"
+    BINDING_MADE = "binding-made"
+    ALIAS_SET = "alias-set"
+    MERGE_DECIDED = "merge-decided"
+    PAGE_FORKED = "page-forked"
+
+
+@dataclass(frozen=True, slots=True)
+class DecisionEvent:
+    """One immutable, ordered decision. ``seq`` is the per-space total order."""
+
+    seq: int
+    space: str
+    type: EventType
+    payload: Mapping[str, Any]
+    actor: str | None = None
+    timestamp: datetime = field(default_factory=lambda: datetime.now(tz=timezone.utc))
+
+
+@dataclass(frozen=True, slots=True)
+class CoordinationState:
+    """The derived fold of a space's log: current aliases + equivalence groups + open overlays.
+
+    Disposable (tier-3): always recomputable from the log via :meth:`DecisionLog.fold`.
+    """
+
+    aliases: Mapping[str, str]
+    equivalence_groups: tuple[frozenset[str], ...]
+    open_overlays: Mapping[str, Mapping[str, Any]]
+
+    def resolve_alias(self, name: str) -> str | None:
+        return self.aliases.get(name)
+
+    def equivalent_to(self, identity: str) -> frozenset[str]:
+        """All identities equivalent to ``identity`` (including itself if bound), else just it."""
+        for group in self.equivalence_groups:
+            if identity in group:
+                return group
+        return frozenset({identity})
+
+
+def serialize_event(event: DecisionEvent) -> bytes:
+    """Deterministic, stable-JSON wire form of an event (same bytes for equal events, any process).
+
+    Sorted keys + compact separators make the serialization canonical, so a git object hashed from
+    it is reproducible — the basis for content-addressable, comparable logs across backends.
+    """
+    obj = {
+        "seq": event.seq,
+        "space": event.space,
+        "type": event.type.value,
+        "payload": event.payload,
+        "actor": event.actor,
+        "timestamp": event.timestamp.isoformat(),
+    }
+    return json.dumps(obj, sort_keys=True, separators=(",", ":"), ensure_ascii=False).encode()
+
+
+def deserialize_event(data: bytes | str) -> DecisionEvent:
+    """Inverse of :func:`serialize_event` — round-trips an event byte-for-byte by field."""
+    obj = json.loads(data)
+    return DecisionEvent(
+        seq=obj["seq"],
+        space=obj["space"],
+        type=EventType(obj["type"]),
+        payload=obj["payload"],
+        actor=obj["actor"],
+        timestamp=datetime.fromisoformat(obj["timestamp"]),
+    )
+
+
+@runtime_checkable
+class EventStore(Protocol):
+    """Append-only, per-space ordered storage behind :class:`DecisionLog`.
+
+    Two bindings exist: :class:`InMemoryEventStore` (default/test double) and
+    :class:`~shard_wiki.coordination.git_event_store.GitEventStore` (git-addressable). Both assign
+    a per-space monotonic ``seq`` at the log head and guarantee read-your-writes for their reach
+    (in-process for memory; cross-process for git).
+    """
+
+    def append(
+        self, space: str, type: EventType, payload: Mapping[str, Any], actor: str | None = None
+    ) -> DecisionEvent: ...
+
+    def events(self, space: str) -> tuple[DecisionEvent, ...]: ...
+
+
+class InMemoryEventStore:
+    """In-process append-only store, totally ordered per space (the append authority for a process).
+
+    The default test double; the git backend preserves this exact contract on durable storage.
+    """
+
+    def __init__(self) -> None:
+        self._events: dict[str, list[DecisionEvent]] = {}
+
+    def append(
+        self,
+        space: str,
+        type: EventType,
+        payload: Mapping[str, Any],
+        actor: str | None = None,
+    ) -> DecisionEvent:
+        seq = len(self._events.get(space, ()))
+        event = DecisionEvent(seq=seq, space=space, type=type, payload=dict(payload), actor=actor)
+        self._events.setdefault(space, []).append(event)
+        return event
+
+    def events(self, space: str) -> tuple[DecisionEvent, ...]:
+        return tuple(self._events.get(space, ()))
+
+
+class DecisionLog:
+    """Append-only decision log, totally ordered per space, with a derived :meth:`fold`.
+
+    Storage is delegated to an :class:`EventStore` (default :class:`InMemoryEventStore`); swapping
+    in the git backend changes only durability + the concurrency model, not this API or the fold.
+    """
+
+    def __init__(self, store: EventStore | None = None) -> None:
+        self._store: EventStore = store if store is not None else InMemoryEventStore()
+
+    def append(
+        self,
+        space: str,
+        type: EventType,
+        payload: Mapping[str, Any],
+        actor: str | None = None,
+    ) -> DecisionEvent:
+        return self._store.append(space, type, payload, actor=actor)
+
+    def events(self, space: str) -> tuple[DecisionEvent, ...]:
+        """The space's events in append (total) order. Read-your-writes: a just-appended event
+        is present immediately."""
+        return self._store.events(space)
+
+    def fold(self, space: str) -> CoordinationState:
+        """Replay the log into current coordination state (derived = f(log))."""
+        aliases: dict[str, str] = {}
+        overlays: dict[str, dict[str, Any]] = {}
+        groups: list[set[str]] = []
+
+        for event in self.events(space):
+            if event.type is EventType.ALIAS_SET:
+                aliases[event.payload["alias"]] = event.payload["target"]
+            elif event.type is EventType.BINDING_MADE:
+                _merge_group(groups, {str(m) for m in event.payload["members"]})
+            elif event.type is EventType.OVERLAY_CREATED:
+                overlays[event.payload["overlay_id"]] = dict(event.payload)
+            elif event.type is EventType.MERGE_DECIDED:
+                # A merge resolution may collapse an overlay; minimal handling for the slice.
+                overlays.pop(event.payload.get("overlay_id", ""), None)
+            elif event.type is EventType.PAGE_FORKED:
+                _merge_group(groups, {str(event.payload["source"]), str(event.payload["fork"])})
+
+        return CoordinationState(
+            aliases=MappingProxyType(dict(aliases)),
+            equivalence_groups=tuple(frozenset(g) for g in groups),
+            open_overlays=MappingProxyType({k: MappingProxyType(v) for k, v in overlays.items()}),
+        )
+
+
+def _merge_group(groups: list[set[str]], members: set[str]) -> None:
+    """Union-merge ``members`` into ``groups`` (any existing group sharing a member absorbs it)."""
+    touching = [g for g in groups if g & members]
+    for g in touching:
+        groups.remove(g)
+        members |= g
+    groups.append(members)

src/shard_wiki/coordination/git_event_store.py

@@ -0,0 +1,172 @@
+"""GitEventStore — a git-addressable binding of :class:`EventStore` (SHARD-WP-0009 T1).
+
+Each space is a ref (``refs/spaces/<sha1(space)>``); each ``append`` writes the event as an
+immutable git object (a one-blob tree committed onto the ref) and advances the ref. The commit
+chain *is* the totally ordered log: ``seq`` is the depth, ``events`` walks first-parent from the
+head oldest→newest. Coordination-canonical state therefore inherits git's history / patch /
+review / backup affordances (I-6) and is read-your-writes correct across processes.
+
+The total order is enforced at storage by a **compare-and-swap** ref update
+(``git update-ref <ref> <new> <old>``): two appenders racing off the same head — the loser's CAS
+fails and it retries off the new head, so a non-holder can never fork the log. The lease layer
+(T2) sits *above* this as the append-authority policy; CAS is the mechanism that makes it safe.
+
+Implemented over the ``git`` CLI through :mod:`subprocess` — zero runtime dependencies.
+"""
+
+from __future__ import annotations
+
+import hashlib
+import os
+import subprocess
+from collections.abc import Mapping
+from pathlib import Path
+from typing import Any
+
+from shard_wiki.coordination.decision_log import (
+    DecisionEvent,
+    EventType,
+    deserialize_event,
+    serialize_event,
+)
+
+__all__ = ["GitEventStore"]
+
+# Fixed identity so commit objects are reproducible and never prompt for git config; the event's
+# own timestamp/actor carry the real provenance, the commit is just the ordered container.
+_GIT_IDENTITY = {
+    "GIT_AUTHOR_NAME": "shard-wiki",
+    "GIT_AUTHOR_EMAIL": "coordination@shard-wiki",
+    "GIT_COMMITTER_NAME": "shard-wiki",
+    "GIT_COMMITTER_EMAIL": "coordination@shard-wiki",
+}
+_EVENT_PATH = "event.json"
+_MAX_CAS_RETRIES = 50
+
+
+class GitEventStore:
+    """Git-backed, append-only, per-space ordered event store (an :class:`EventStore`)."""
+
+    def __init__(self, repo_path: str | Path) -> None:
+        self.repo_path = Path(repo_path)
+        self.repo_path.mkdir(parents=True, exist_ok=True)
+        if not (self.repo_path / "HEAD").exists() and not (self.repo_path / ".git").exists():
+            self._git("init", "--quiet", str(self.repo_path), at_cwd=True)
+
+    # -- EventStore contract -------------------------------------------------
+
+    def append(
+        self,
+        space: str,
+        type: EventType,
+        payload: Mapping[str, Any],
+        actor: str | None = None,
+    ) -> DecisionEvent:
+        """Append one event, advancing the space ref under compare-and-swap (retry-on-race)."""
+        ref = self._ref(space)
+        for _ in range(_MAX_CAS_RETRIES):
+            head = self._head(ref)
+            seq = self._count(ref, head)
+            event = DecisionEvent(
+                seq=seq, space=space, type=type, payload=dict(payload), actor=actor
+            )
+            commit = self._commit_event(event, parent=head)
+            if self._cas_update(ref, new=commit, old=head):
+                return event
+        raise RuntimeError(f"append contention on {space!r}: exhausted {_MAX_CAS_RETRIES} retries")
+
+    def import_event(self, event: DecisionEvent) -> None:
+        """Replay one pre-existing event *verbatim* (preserving seq / timestamp / actor) onto its
+        space ref — the one-time migration path (SHARD-WP-0009 T4), not a live append.
+
+        Refuses out-of-order import so the imported chain stays a contiguous total order; preserving
+        the original fields keeps provenance intact (union-without-erasure) rather than restamping.
+        """
+        ref = self._ref(event.space)
+        head = self._head(ref)
+        expected = self._count(ref, head)
+        if event.seq != expected:
+            raise ValueError(
+                f"out-of-order import on {event.space!r}: expected seq {expected}, got {event.seq}"
+            )
+        commit = self._commit_event(event, parent=head)
+        if not self._cas_update(ref, new=commit, old=head):
+            raise RuntimeError(f"import race on {ref}")
+
+    def events(self, space: str) -> tuple[DecisionEvent, ...]:
+        """The space's events oldest→newest (append/total order)."""
+        ref = self._ref(space)
+        head = self._head(ref)
+        if head is None:
+            return ()
+        shas = self._git("rev-list", "--reverse", "--first-parent", ref).decode().split()
+        return tuple(
+            deserialize_event(self._git("cat-file", "blob", f"{sha}:{_EVENT_PATH}"))
+            for sha in shas
+        )
+
+    # -- git plumbing --------------------------------------------------------
+
+    def _commit_event(self, event: DecisionEvent, parent: str | None) -> str:
+        blob = self._git(
+            "hash-object", "-w", "--stdin", stdin=serialize_event(event)
+        ).decode().strip()
+        tree = self._git(
+            "mktree", stdin=f"100644 blob {blob}\t{_EVENT_PATH}\n".encode()
+        ).decode().strip()
+        args = ["commit-tree", tree, "-m", f"event {event.seq} {event.type.value}"]
+        if parent is not None:
+            args += ["-p", parent]
+        # Pin the commit date to the event's timestamp for reproducible objects.
+        date = event.timestamp.isoformat()
+        env = {**_GIT_IDENTITY, "GIT_AUTHOR_DATE": date, "GIT_COMMITTER_DATE": date}
+        return self._git(*args, env=env).decode().strip()
+
+    def _cas_update(self, ref: str, new: str, old: str | None) -> bool:
+        """``git update-ref`` with the old value as a CAS guard (empty oldvalue == must-not-exist).
+
+        Returns False if the ref moved since we read ``old`` (lost the race) — the caller retries.
+        """
+        result = self._run("update-ref", ref, new, old if old is not None else "")
+        return result.returncode == 0
+
+    def _head(self, ref: str) -> str | None:
+        result = self._run("rev-parse", "--verify", "--quiet", ref)
+        out = result.stdout.decode().strip()
+        return out or None
+
+    def _count(self, ref: str, head: str | None) -> int:
+        if head is None:
+            return 0
+        return int(self._git("rev-list", "--count", "--first-parent", ref).decode().strip())
+
+    @staticmethod
+    def _ref(space: str) -> str:
+        return f"refs/spaces/{hashlib.sha1(space.encode()).hexdigest()}"
+
+    def _git(
+        self,
+        *args: str,
+        stdin: bytes | None = None,
+        env: dict | None = None,
+        at_cwd: bool = False,
+    ) -> bytes:
+        result = self._run(*args, stdin=stdin, env=env, at_cwd=at_cwd, check=True)
+        return result.stdout
+
+    def _run(
+        self,
+        *args: str,
+        stdin: bytes | None = None,
+        env: dict | None = None,
+        at_cwd: bool = False,
+        check: bool = False,
+    ) -> subprocess.CompletedProcess:
+        base = ["git"] if at_cwd else ["git", "-C", str(self.repo_path)]
+        return subprocess.run(
+            [*base, *args],
+            input=stdin,
+            capture_output=True,
+            env={**os.environ, **(env or {})},
+            check=check,
+        )

src/shard_wiki/coordination/migration.py

@@ -0,0 +1,53 @@
+"""One-time migration of a coordination log into git (SHARD-WP-0009 T4).
+
+Replays an existing decision log — an in-memory store, or a JSON-lines export — into a
+:class:`GitEventStore`, preserving each event verbatim (seq / timestamp / actor) so provenance
+survives the move (union-without-erasure). After migration the same :meth:`DecisionLog.fold`
+reproduces identical coordination state; only durability changes.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Iterable
+from pathlib import Path
+
+from shard_wiki.coordination.decision_log import (
+    DecisionEvent,
+    EventStore,
+    deserialize_event,
+    serialize_event,
+)
+from shard_wiki.coordination.git_event_store import GitEventStore
+
+__all__ = ["import_log", "migrate_space", "export_jsonl", "import_jsonl"]
+
+
+def import_log(events: Iterable[DecisionEvent], dest: GitEventStore) -> int:
+    """Replay ``events`` (in space/seq order) into ``dest``. Returns the count imported."""
+    count = 0
+    for event in events:
+        dest.import_event(event)
+        count += 1
+    return count
+
+
+def migrate_space(source: EventStore, space: str, dest: GitEventStore) -> int:
+    """Migrate one space's log from any :class:`EventStore` into the git backend verbatim."""
+    return import_log(source.events(space), dest)
+
+
+def export_jsonl(events: Iterable[DecisionEvent], path: str | Path) -> int:
+    """Write events as newline-delimited canonical JSON (a portable, diffable log export)."""
+    count = 0
+    with open(path, "wb") as handle:
+        for event in events:
+            handle.write(serialize_event(event) + b"\n")
+            count += 1
+    return count
+
+
+def import_jsonl(path: str | Path, dest: GitEventStore) -> int:
+    """Replay a JSON-lines export (see :func:`export_jsonl`) into the git backend."""
+    with open(path, "rb") as handle:
+        events = [deserialize_event(line) for line in handle if line.strip()]
+    return import_log(events, dest)

src/shard_wiki/coordination/overlay.py

@@ -0,0 +1,134 @@
+"""Overlay engine — overlay-before-mutation (FederationRequirements ADR-05, blueprint §8.2).
+
+An overlay is a non-destructive local edit against a page. It is **coordination-canonical**: an
+``OVERLAY_CREATED`` event in the decision log (§8.1), not a mutable side file. The current set
+of open overlays is the log fold. ``draft`` records one; ``apply`` (T4) resolves it under drift.
+"""
+
+from __future__ import annotations
+
+import uuid
+from collections.abc import Mapping
+from dataclasses import dataclass
+from enum import Enum
+from typing import Any
+
+from shard_wiki.adapters import ShardAdapter
+from shard_wiki.coordination.decision_log import DecisionLog, EventType
+from shard_wiki.model import Identity, Page, Verb
+from shard_wiki.provenance import OverlayState
+
+__all__ = ["Overlay", "OverlayEngine", "ApplyStatus", "ApplyResult"]
+
+
+@dataclass(frozen=True, slots=True)
+class Overlay:
+    """A non-destructive edit: the proposed ``body`` for ``target``, authored against
+    ``base_rev`` (the shard revision seen at draft time, for drift detection)."""
+
+    overlay_id: str
+    target: Identity
+    base_rev: str | None
+    body: str
+    state: OverlayState = OverlayState.DRAFT
+
+    def to_payload(self) -> dict[str, Any]:
+        return {
+            "overlay_id": self.overlay_id,
+            "target_shard": self.target.shard,
+            "target_key": self.target.key,
+            "base_rev": self.base_rev,
+            "body": self.body,
+            "state": self.state.value,
+        }
+
+    @classmethod
+    def from_payload(cls, payload: Mapping[str, Any]) -> Overlay:
+        return cls(
+            overlay_id=payload["overlay_id"],
+            target=Identity(payload["target_shard"], payload["target_key"]),
+            base_rev=payload["base_rev"],
+            body=payload["body"],
+            state=OverlayState(payload.get("state", OverlayState.DRAFT.value)),
+        )
+
+
+class ApplyStatus(Enum):
+    APPLIED = "applied"  # fast-forwarded and written through
+    REFUSED_DRIFT = "refused-drift"  # source moved under the overlay; no clobber
+    KEPT_DRAFT = "kept-draft"  # target read-only; overlay remains the local truth
+
+
+@dataclass(frozen=True, slots=True)
+class ApplyResult:
+    status: ApplyStatus
+    overlay_id: str
+    page: Page | None = None
+    detail: str = ""
+
+
+class OverlayEngine:
+    def __init__(self, space: str, log: DecisionLog) -> None:
+        self.space = space
+        self.log = log
+
+    def draft(
+        self,
+        target: Identity,
+        body: str,
+        base_rev: str | None,
+        actor: str | None = None,
+    ) -> Overlay:
+        """Create a draft overlay and record it in the decision log (coordination-canonical)."""
+        overlay = Overlay(uuid.uuid4().hex, target, base_rev, body)
+        self.log.append(self.space, EventType.OVERLAY_CREATED, overlay.to_payload(), actor=actor)
+        return overlay
+
+    def get(self, overlay_id: str) -> Overlay | None:
+        payload = self.log.fold(self.space).open_overlays.get(overlay_id)
+        return Overlay.from_payload(payload) if payload is not None else None
+
+    def open_overlays(self) -> tuple[Overlay, ...]:
+        state = self.log.fold(self.space)
+        return tuple(Overlay.from_payload(p) for p in state.open_overlays.values())
+
+    def apply(self, overlay_id: str, adapter: ShardAdapter) -> ApplyResult:
+        """Resolve an overlay against its target shard with apply-under-drift semantics (§8.6).
+
+        Read-only target → ``KEPT_DRAFT`` (the overlay stays the local truth). Otherwise compare
+        the overlay's ``base_rev`` to the shard's current rev: equal → fast-forward write-through
+        (``APPLIED``); changed → ``REFUSED_DRIFT`` (never clobber, I-5). Applying records a
+        ``MERGE_DECIDED`` event that closes the overlay in the fold.
+        """
+        overlay = self.get(overlay_id)
+        if overlay is None:
+            raise KeyError(overlay_id)
+        if adapter.shard_id != overlay.target.shard:
+            raise ValueError(f"adapter {adapter.shard_id!r} != target {overlay.target.shard!r}")
+
+        if not adapter.profile().supports(Verb.WRITE):
+            return ApplyResult(
+                ApplyStatus.KEPT_DRAFT, overlay_id, detail="target is read-only; overlay retained"
+            )
+
+        current = _current_rev(adapter, overlay.target.key)
+        if current != overlay.base_rev:
+            return ApplyResult(
+                ApplyStatus.REFUSED_DRIFT,
+                overlay_id,
+                detail=f"base_rev {overlay.base_rev!r} != current {current!r}",
+            )
+
+        page = adapter.write(overlay.target.key, overlay.body)
+        self.log.append(
+            self.space,
+            EventType.MERGE_DECIDED,
+            {"overlay_id": overlay_id, "outcome": "applied"},
+        )
+        return ApplyResult(ApplyStatus.APPLIED, overlay_id, page=page)
+
+
+def _current_rev(adapter: ShardAdapter, key: str) -> str | None:
+    """Best-effort current-revision probe; adapters without one are treated as no-rev."""
+    probe = getattr(adapter, "current_rev", None)
+    return probe(key) if callable(probe) else None

src/shard_wiki/coordination/patch.py

@@ -0,0 +1,38 @@
+"""Patch rendering — an overlay as a reviewable diff (FederationRequirements ADR-05).
+
+A pure function over (base body, overlay body): the auditable change proposal that an overlay
+becomes before it is applied. Markdown/native text in this slice (lossless); a lossy
+native-syntax-with-fidelity-report variant is later (TSD §A.6).
+"""
+
+from __future__ import annotations
+
+import difflib
+from dataclasses import dataclass
+
+from shard_wiki.coordination.overlay import Overlay
+from shard_wiki.model import Identity
+
+__all__ = ["Patch", "render_patch"]
+
+
+@dataclass(frozen=True, slots=True)
+class Patch:
+    target: Identity
+    diff: str
+
+    @property
+    def is_empty(self) -> bool:
+        return self.diff == ""
+
+
+def render_patch(overlay: Overlay, base_body: str) -> Patch:
+    """Render ``base_body`` → ``overlay.body`` as a unified diff against the overlay target."""
+    label = str(overlay.target)
+    lines = difflib.unified_diff(
+        base_body.splitlines(keepends=True),
+        overlay.body.splitlines(keepends=True),
+        fromfile=f"a/{label}",
+        tofile=f"b/{label}",
+    )
+    return Patch(target=overlay.target, diff="".join(lines))

src/shard_wiki/engine/__init__.py

@@ -0,0 +1,49 @@
+"""engine/ — shard-wiki's native, headless wiki engine (a canonical-mode shard backend).
+
+A small page-store kernel + a typed-extension runtime (WikiEngineCoreArchitecture). The engine
+is *one shard*: it is consumed by the orchestrator only via its `EngineShardAdapter`; it never
+imports the derived tier (`union`/`projection`).
+"""
+
+from shard_wiki.engine.activation import (
+    ActivationContext,
+    ActivationProvider,
+    ActivationResolver,
+    StaticProvider,
+    feature_control_provider,
+)
+from shard_wiki.engine.extension import (
+    ActiveExtensions,
+    Extension,
+    ExtensionError,
+    ExtensionRuntime,
+    Hook,
+)
+from shard_wiki.engine.adapter import EngineShardAdapter, build_engine_shard
+from shard_wiki.engine.kernel import EngineKernel
+from shard_wiki.engine.links import extract_wikilinks
+from shard_wiki.engine.profile import (
+    ProfileContribution,
+    derive_profile,
+    engine_base_profile,
+)
+
+__all__ = [
+    "EngineKernel",
+    "extract_wikilinks",
+    "Hook",
+    "Extension",
+    "ExtensionError",
+    "ExtensionRuntime",
+    "ActiveExtensions",
+    "ActivationContext",
+    "ActivationProvider",
+    "StaticProvider",
+    "ActivationResolver",
+    "feature_control_provider",
+    "engine_base_profile",
+    "ProfileContribution",
+    "derive_profile",
+    "EngineShardAdapter",
+    "build_engine_shard",
+]

src/shard_wiki/engine/activation.py

@@ -0,0 +1,129 @@
+"""Per-shard extension activation (WikiEngineCoreArchitecture E-4/E-8, ADR-0001).
+
+Decides *which registered extensions are active* for a given shard — **availability only, never
+authorization**. The mechanism is OpenFeature-shaped and **provider-pluggable**:
+
+- :class:`StaticProvider` is the **standalone / L0 default** — zero external dependency, in-process
+  flags with optional per-shard scoping. A kernel-only or offline shard uses this.
+- :func:`feature_control_provider` lazily wraps the helix_forge ``feature_control_sdk`` (over
+  OpenFeature) when it is installed; absent, it returns ``None`` and the caller falls back to the
+  static default. This mirrors shard-wiki's identity-provider ladder (local default → external
+  when present), and keeps the engine core pure-stdlib.
+
+An *activation profile* is ``{extension id → config}``; the active id set then feeds the
+extension runtime's `activate()` (T2) and the derived capability profile (T4, E-5).
+"""
+
+from __future__ import annotations
+
+from collections.abc import Iterable, Mapping
+from dataclasses import dataclass, field
+from typing import Any, Protocol, runtime_checkable
+
+__all__ = [
+    "ActivationContext",
+    "ActivationProvider",
+    "StaticProvider",
+    "ActivationResolver",
+    "feature_control_provider",
+]
+
+
+@dataclass(frozen=True, slots=True)
+class ActivationContext:
+    """Scope for an activation decision. Carries no principal/authz — availability only."""
+
+    shard_id: str
+    tenant_id: str | None = None
+    extra: Mapping[str, Any] = field(default_factory=dict)
+
+    def as_dict(self) -> dict[str, Any]:
+        d: dict[str, Any] = {"shard_id": self.shard_id}
+        if self.tenant_id is not None:
+            d["tenant_id"] = self.tenant_id
+        d.update(self.extra)
+        return d
+
+
+@runtime_checkable
+class ActivationProvider(Protocol):
+    """Evaluates feature availability for an extension key in a context (OpenFeature-shaped)."""
+
+    def is_active(self, feature_key: str, context: Mapping[str, Any]) -> bool: ...
+
+    def config(self, feature_key: str, context: Mapping[str, Any]) -> Mapping[str, Any]: ...
+
+
+@dataclass(frozen=True, slots=True)
+class StaticProvider:
+    """The standalone default: in-process flags, optionally overridden per shard. Zero deps.
+
+    ``flags`` is the base availability map; ``per_shard[shard_id]`` overrides it for one shard;
+    ``configs[feature_key]`` supplies per-extension config. Unknown keys → ``default``.
+    """
+
+    flags: Mapping[str, bool] = field(default_factory=dict)
+    per_shard: Mapping[str, Mapping[str, bool]] = field(default_factory=dict)
+    configs: Mapping[str, Mapping[str, Any]] = field(default_factory=dict)
+    default: bool = False
+
+    def is_active(self, feature_key: str, context: Mapping[str, Any]) -> bool:
+        shard = context.get("shard_id")
+        scoped = self.per_shard.get(shard, {}) if shard is not None else {}
+        if feature_key in scoped:
+            return scoped[feature_key]
+        return self.flags.get(feature_key, self.default)
+
+    def config(self, feature_key: str, context: Mapping[str, Any]) -> Mapping[str, Any]:
+        return self.configs.get(feature_key, {})
+
+
+class ActivationResolver:
+    """Maps candidate extension ids → the active set / activation profile for a context."""
+
+    def __init__(self, provider: ActivationProvider) -> None:
+        self.provider = provider
+
+    def active_extensions(
+        self, candidate_ids: Iterable[str], context: ActivationContext
+    ) -> set[str]:
+        ctx = context.as_dict()
+        return {eid for eid in candidate_ids if self.provider.is_active(eid, ctx)}
+
+    def activation_profile(
+        self, candidate_ids: Iterable[str], context: ActivationContext
+    ) -> dict[str, Mapping[str, Any]]:
+        """``{extension id → config}`` for the active subset."""
+        ctx = context.as_dict()
+        return {
+            eid: self.provider.config(eid, ctx)
+            for eid in candidate_ids
+            if self.provider.is_active(eid, ctx)
+        }
+
+
+def feature_control_provider(domain: str | None = None) -> ActivationProvider | None:
+    """Return a feature-control-backed provider if ``feature_control_sdk`` is importable, else
+    ``None`` (caller falls back to :class:`StaticProvider`). Lazy import keeps the engine core
+    dependency-free (ADR-0001)."""
+    try:  # optional engine extra — not a core dependency
+        from feature_control_sdk import FeatureControlClient  # type: ignore
+    except ImportError:
+        return None
+
+    client = FeatureControlClient(domain=domain)
+
+    @dataclass(frozen=True, slots=True)
+    class _FeatureControlProvider:
+        _client: Any
+
+        def is_active(self, feature_key: str, context: Mapping[str, Any]) -> bool:
+            return bool(
+                self._client.get_boolean_value(feature_key, False, context=dict(context))
+            )
+
+        def config(self, feature_key: str, context: Mapping[str, Any]) -> Mapping[str, Any]:
+            getter = getattr(self._client, "get_object_value", None)
+            return dict(getter(feature_key, {}, context=dict(context))) if getter else {}
+
+    return _FeatureControlProvider(client)

src/shard_wiki/engine/adapter.py

@@ -0,0 +1,82 @@
+"""EngineShardAdapter — the engine exposed as a canonical-mode shard (WikiEngineCoreArchitecture
+§6, E-1/E-5).
+
+The engine is *one shard*: the orchestrator consumes it only through this `ShardAdapter`. The
+adapter is backed by the kernel (T1) + a composed extension set (T2/T3); its §A capability
+profile is **derived from the active extensions** (T4), so the orchestrator sees an honest,
+conformance-verifiable profile that reflects exactly what is activated. Read/write run the
+extensions' transform hooks; everything above this stays in the orchestrator (no union/projection
+import).
+"""
+
+from __future__ import annotations
+
+from collections.abc import Iterable
+
+from shard_wiki.adapters import ShardAdapter
+from shard_wiki.engine.activation import ActivationContext, ActivationProvider, ActivationResolver
+from shard_wiki.engine.extension import ActiveExtensions, ExtensionRuntime, Hook
+from shard_wiki.engine.kernel import EngineKernel
+from shard_wiki.engine.profile import derive_profile
+from shard_wiki.model import CapabilityProfile, NotSupported, Page, Verb
+
+__all__ = ["EngineShardAdapter", "build_engine_shard"]
+
+
+class EngineShardAdapter(ShardAdapter):
+    def __init__(
+        self,
+        kernel: EngineKernel,
+        active: ActiveExtensions,
+        base_profile: CapabilityProfile | None = None,
+    ) -> None:
+        self._kernel = kernel
+        self._active = active
+        self._profile = derive_profile(active, base_profile)  # validated (E-5)
+
+    @property
+    def shard_id(self) -> str:
+        return self._kernel.shard_id
+
+    def profile(self) -> CapabilityProfile:
+        return self._profile
+
+    def keys(self) -> Iterable[str]:
+        return self._kernel.keys()
+
+    def read(self, key: str) -> Page:
+        page = self._kernel.read(key)
+        return self._active.dispatch_transform(Hook.ON_READ, page, {"shard_id": self.shard_id})
+
+    def current_rev(self, key: str) -> str | None:
+        return self._kernel.current_rev(key)
+
+    def write(self, key: str, body: str) -> Page:
+        if not self._profile.supports(Verb.WRITE):
+            raise NotSupported(f"{type(self).__name__} ({self.shard_id}) is read-only")
+        body = self._active.dispatch_transform(
+            Hook.ON_WRITE, body, {"shard_id": self.shard_id, "key": key}
+        )
+        return self._kernel.write(key, body)
+
+
+def build_engine_shard(
+    shard_id: str,
+    runtime: ExtensionRuntime,
+    *,
+    activate: Iterable[str] | None = None,
+    provider: ActivationProvider | None = None,
+    context: ActivationContext | None = None,
+    base_profile: CapabilityProfile | None = None,
+) -> EngineShardAdapter:
+    """Stand up an engine shard: resolve which extensions are active (explicit ``activate`` ids,
+    or via an activation ``provider`` over the runtime's available set), compose them, and wrap a
+    fresh kernel as a `ShardAdapter`.
+    """
+    if provider is not None:
+        ctx = context or ActivationContext(shard_id)
+        ids = ActivationResolver(provider).active_extensions(runtime.available(), ctx)
+    else:
+        ids = set(activate or ())
+    active = runtime.activate(ids)
+    return EngineShardAdapter(EngineKernel(shard_id), active, base_profile)

src/shard_wiki/engine/extension.py

@@ -0,0 +1,165 @@
+"""Typed-extension runtime — the engine framework (WikiEngineCoreArchitecture §4, E-3/E-9).
+
+Everything beyond the kernel's c2-minimum is an :class:`Extension`: it declares a typed
+contract (id, provided capabilities, declared types, bound hooks, dependencies, conflicts) and
+the runtime **composes** an activation set deterministically, **rejecting impossible profiles**
+(unmet deps / conflicts / type collisions) — the §6.5 capability-as-data discipline applied to
+extensions. Extension structure is **verified at registration** (mirrors §6.6 conformance):
+bad ids or non-callable hook handlers are refused, so the framework acts on verified data.
+
+Hooks are dispatched in a declared, deterministic order (dependency-topological, ties by id):
+*transform* hooks chain a payload through handlers; *collect* hooks gather contributions.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Callable, Iterable, Mapping
+from enum import Enum
+from typing import Any, ClassVar
+
+__all__ = ["Hook", "Extension", "ExtensionError", "ExtensionRuntime", "ActiveExtensions"]
+
+
+class ExtensionError(ValueError):
+    """Raised when an extension is malformed or an activation set is impossible (§6.5)."""
+
+
+class Hook(Enum):
+    # transform hooks: each handler takes (payload, ctx) and returns the next payload
+    ON_WRITE = "on_write"      # transform a draft before persist
+    ON_READ = "on_read"        # transform a page on read
+    ON_RESOLVE = "on_resolve"  # transform a name resolution
+    ON_RENDER = "on_render"    # produce a derived representation
+    # collect hooks: each handler takes (payload, ctx) and returns a contribution
+    ON_LINK = "on_link"        # contribute link/transclusion edges
+    ON_QUERY = "on_query"      # answer a query
+    ON_PROFILE = "on_profile"  # contribute capability-profile positions (E-5)
+
+
+_TRANSFORM = frozenset({Hook.ON_WRITE, Hook.ON_READ, Hook.ON_RESOLVE, Hook.ON_RENDER})
+_COLLECT = frozenset({Hook.ON_LINK, Hook.ON_QUERY, Hook.ON_PROFILE})
+
+
+class Extension:
+    """Base class for a typed extension. Subclasses set the class vars and override
+    :meth:`hooks` to bind handlers (signature ``handler(payload, ctx) -> result``)."""
+
+    id: ClassVar[str] = ""
+    provides: ClassVar[tuple[str, ...]] = ()
+    declares_types: ClassVar[tuple[str, ...]] = ()
+    depends_on: ClassVar[tuple[str, ...]] = ()
+    conflicts_with: ClassVar[tuple[str, ...]] = ()
+
+    def hooks(self) -> Mapping[Hook, Callable[[Any, Any], Any]]:
+        return {}
+
+
+class ActiveExtensions:
+    """A composed, ordered activation set with deterministic hook dispatch."""
+
+    def __init__(self, ordered: list[Extension]) -> None:
+        self._ordered = ordered
+        self.ids: tuple[str, ...] = tuple(e.id for e in ordered)
+        self._tables: dict[Hook, list[tuple[str, Callable[[Any, Any], Any]]]] = {}
+        for ext in ordered:
+            for hook, fn in ext.hooks().items():
+                self._tables.setdefault(hook, []).append((ext.id, fn))
+
+    def handlers(self, hook: Hook) -> tuple[str, ...]:
+        """The extension ids bound to ``hook``, in dispatch order (for introspection)."""
+        return tuple(eid for eid, _ in self._tables.get(hook, ()))
+
+    def dispatch_transform(self, hook: Hook, payload: Any, ctx: Any = None) -> Any:
+        if hook not in _TRANSFORM:
+            raise ExtensionError(f"{hook} is not a transform hook")
+        for _eid, fn in self._tables.get(hook, ()):
+            payload = fn(payload, ctx)
+        return payload
+
+    def dispatch_collect(self, hook: Hook, payload: Any = None, ctx: Any = None) -> list[Any]:
+        if hook not in _COLLECT:
+            raise ExtensionError(f"{hook} is not a collect hook")
+        return [fn(payload, ctx) for _eid, fn in self._tables.get(hook, ())]
+
+
+class ExtensionRuntime:
+    def __init__(self) -> None:
+        self._registered: dict[str, Extension] = {}
+
+    def available(self) -> frozenset[str]:
+        """Ids of all registered extensions (the candidate set for activation)."""
+        return frozenset(self._registered)
+
+    def register(self, ext: Extension) -> Extension:
+        """Register an extension after structural verification (mirrors §6.6)."""
+        if not ext.id or not ext.id.startswith("ext."):
+            raise ExtensionError(f"extension id must be 'ext.<name>', got {ext.id!r}")
+        if ext.id in self._registered:
+            raise ExtensionError(f"duplicate extension id: {ext.id}")
+        bound = ext.hooks()
+        for hook, fn in bound.items():
+            if not isinstance(hook, Hook):
+                raise ExtensionError(f"{ext.id}: hook key {hook!r} is not a Hook")
+            if not callable(fn):
+                raise ExtensionError(f"{ext.id}: handler for {hook} is not callable")
+        self._registered[ext.id] = ext
+        return ext
+
+    def activate(self, ids: Iterable[str]) -> ActiveExtensions:
+        """Compose an activation set: dependency closure → conflict/type checks → deterministic
+        order. Raises :class:`ExtensionError` on an impossible profile."""
+        requested = set(ids)
+        unknown = requested - self._registered.keys()
+        if unknown:
+            raise ExtensionError(f"unknown extensions: {sorted(unknown)}")
+
+        # dependency closure
+        active: set[str] = set()
+        frontier = list(requested)
+        while frontier:
+            eid = frontier.pop()
+            if eid in active:
+                continue
+            ext = self._registered.get(eid)
+            if ext is None:
+                raise ExtensionError(f"unmet dependency: {eid}")
+            active.add(eid)
+            frontier.extend(d for d in ext.depends_on if d not in active)
+
+        exts = [self._registered[e] for e in active]
+
+        # conflicts
+        for ext in exts:
+            clash = active & set(ext.conflicts_with)
+            if clash:
+                raise ExtensionError(f"{ext.id} conflicts with active {sorted(clash)}")
+
+        # type collisions (two active extensions claiming the same type id)
+        owner: dict[str, str] = {}
+        for ext in exts:
+            for t in ext.declares_types:
+                if t in owner:
+                    raise ExtensionError(
+                        f"type collision on {t!r}: {owner[t]} and {ext.id}"
+                    )
+                owner[t] = ext.id
+
+        return ActiveExtensions(self._topo_order(exts))
+
+    def _topo_order(self, exts: list[Extension]) -> list[Extension]:
+        """Dependencies before dependents; ties broken by id (deterministic)."""
+        by_id = {e.id: e for e in exts}
+        ordered: list[Extension] = []
+        placed: set[str] = set()
+
+        def visit(ext: Extension) -> None:
+            if ext.id in placed:
+                return
+            for dep in sorted(d for d in ext.depends_on if d in by_id):
+                visit(by_id[dep])
+            placed.add(ext.id)
+            ordered.append(ext)
+
+        for ext in sorted(exts, key=lambda e: e.id):
+            visit(ext)
+        return ordered

src/shard_wiki/engine/extensions/__init__.py

@@ -0,0 +1,10 @@
+"""engine/extensions/ — built-in typed extensions for the wiki engine.
+
+Each is a typed :class:`~shard_wiki.engine.extension.Extension` a shard activates only if needed.
+``ext.struct`` (typed records) is the first; more (views, addressing, computational, authz) follow
+the same pattern.
+"""
+
+from shard_wiki.engine.extensions.struct import StructExt, parse_frontmatter
+
+__all__ = ["StructExt", "parse_frontmatter"]

src/shard_wiki/engine/extensions/struct.py

@@ -0,0 +1,81 @@
+"""ext.struct — typed records, a first built-in extension (WikiEngineCoreArchitecture X-STRUCT).
+
+Demonstrates the typed-extension framework end-to-end. A page may carry a leading in-text
+frontmatter block (`---` … `---`, `key: value` lines — git-diffable structure, blueprint T12).
+With this extension **active**, the engine:
+
+- **ON_WRITE** validates the structured block (optionally against an allowed-field set) — a
+  malformed/disallowed structured page is rejected; the body is otherwise unchanged
+  (content-preserving, so write conformance holds);
+- **ON_READ** tags such pages as `PageShape.TYPED_RECORD`;
+- **ON_PROFILE** raises the shard's profile with the `structured-payload` verb (E-5).
+
+With the extension **inactive**, the kernel treats the same page as opaque prose — the feature
+is genuinely absent (honest profile). This is "activate only what you need" in action.
+"""
+
+from __future__ import annotations
+
+import dataclasses
+from collections.abc import Iterable, Mapping
+from typing import Any
+
+from shard_wiki.engine.extension import Extension, Hook
+from shard_wiki.engine.profile import ProfileContribution
+from shard_wiki.model import Page, PageShape, Verb
+
+__all__ = ["StructExt", "parse_frontmatter"]
+
+
+def parse_frontmatter(body: str) -> tuple[dict[str, str], bool]:
+    """Parse a leading ``---`` … ``---`` block of ``key: value`` lines.
+
+    Returns ``(fields, has_block)``. An unterminated opening ``---`` is *not* a valid block.
+    """
+    lines = body.splitlines()
+    if not lines or lines[0].strip() != "---":
+        return {}, False
+    fields: dict[str, str] = {}
+    for line in lines[1:]:
+        if line.strip() == "---":
+            return fields, True
+        if ":" in line:
+            key, _, value = line.partition(":")
+            fields[key.strip()] = value.strip()
+    return {}, False  # no closing fence → not a frontmatter block
+
+
+class StructExt(Extension):
+    id = "ext.struct"
+    declares_types = ("record",)
+    provides = ("capability.wiki.page-model",)
+
+    def __init__(self, allowed_fields: Iterable[str] | None = None) -> None:
+        self._allowed: set[str] | None = set(allowed_fields) if allowed_fields is not None else None
+
+    def hooks(self) -> Mapping[Hook, Any]:
+        return {
+            Hook.ON_WRITE: self._on_write,
+            Hook.ON_READ: self._on_read,
+            Hook.ON_PROFILE: self._on_profile,
+        }
+
+    def _on_write(self, body: str, ctx: Any) -> str:
+        fields, has_block = parse_frontmatter(body)
+        if has_block and self._allowed is not None:
+            disallowed = set(fields) - self._allowed
+            if disallowed:
+                raise ValueError(f"ext.struct: disallowed fields {sorted(disallowed)}")
+        return body  # structure stays in-text (git-diffable); body unchanged
+
+    def _on_read(self, page: Page, ctx: Any) -> Page:
+        _, has_block = parse_frontmatter(page.body)
+        return dataclasses.replace(page, shape=PageShape.TYPED_RECORD) if has_block else page
+
+    def _on_profile(self, payload: Any, ctx: Any) -> ProfileContribution:
+        return ProfileContribution(verbs_add=frozenset({Verb.STRUCTURED_PAYLOAD}))
+
+    @staticmethod
+    def fields(body: str) -> dict[str, str]:
+        """Parsed structured fields of a page body (empty if it has no frontmatter block)."""
+        return parse_frontmatter(body)[0]

src/shard_wiki/engine/kernel.py

@@ -0,0 +1,87 @@
+"""Engine kernel — the small page-store core (WikiEngineCoreArchitecture §3, EC-1…EC-4).
+
+The irreducible engine: author/read/edit pages (edit = a new version; delete = a recoverable
+tombstone — history is the floor, I-10), enumerate keys, and resolve `[[wikilinks]]` (red-link =
+an unresolved target). No feature beyond this c2-minimum lives in the kernel; everything else is
+a typed extension (E-3).
+
+Storage is intentionally simple here (in-memory version history); the git-IS-store backing
+(SHARD-WP-0009/0012) slots in behind the same API later. The kernel reuses the page model and
+provenance leaf; it does not redefine them.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Iterable
+from datetime import datetime, timezone
+
+from shard_wiki.engine.links import extract_wikilinks
+from shard_wiki.model import Identity, Page, Placement
+from shard_wiki.provenance import Liveness, ProvenanceEnvelope, Staleness
+
+__all__ = ["EngineKernel"]
+
+
+class EngineKernel:
+    """An in-process page store with per-page version history for one engine shard."""
+
+    def __init__(self, shard_id: str) -> None:
+        self.shard_id = shard_id
+        self._versions: dict[str, list[Page]] = {}
+        self._deleted: set[str] = set()
+
+    # --- write path (create/edit are one operation; both append a version) ---
+    def write(self, key: str, body: str) -> Page:
+        versions = self._versions.setdefault(key, [])
+        rev = str(len(versions) + 1)
+        page = Page(
+            identity=Identity(self.shard_id, key),
+            body=body,
+            envelope=ProvenanceEnvelope(
+                source_shard=self.shard_id,
+                liveness=Liveness.STATIC,
+                staleness=Staleness.FRESH,
+                source_rev=rev,
+                observed_at=datetime.now(tz=timezone.utc),
+            ),
+            placements=(Placement(self.shard_id, key),),
+        )
+        versions.append(page)
+        self._deleted.discard(key)
+        return page
+
+    # --- read path ---
+    def exists(self, key: str) -> bool:
+        return key in self._versions and key not in self._deleted
+
+    def read(self, key: str) -> Page:
+        """Latest version of a live page. Raises ``KeyError`` if absent or deleted."""
+        if not self.exists(key):
+            raise KeyError(key)
+        return self._versions[key][-1]
+
+    def keys(self) -> Iterable[str]:
+        return (k for k in sorted(self._versions) if k not in self._deleted)
+
+    def current_rev(self, key: str) -> str | None:
+        return self._versions[key][-1].envelope.source_rev if self.exists(key) else None
+
+    # --- history & recoverability (I-10): versions are retained across delete ---
+    def history(self, key: str) -> tuple[Page, ...]:
+        """All versions ever written for ``key`` (oldest→newest), even after delete."""
+        return tuple(self._versions.get(key, ()))
+
+    def delete(self, key: str) -> None:
+        """Tombstone a page (history retained; restore by writing again)."""
+        if key not in self._versions:
+            raise KeyError(key)
+        self._deleted.add(key)
+
+    # --- links (EC-4): resolution + red-link detection within this shard ---
+    def links(self, key: str) -> list[str]:
+        """Wikilink targets in a page's current body."""
+        return extract_wikilinks(self.read(key).body)
+
+    def resolve_link(self, target: str) -> Identity | None:
+        """Resolve a wikilink target to a live page identity, or ``None`` (a **red-link**)."""
+        return self.read(target).identity if self.exists(target) else None

src/shard_wiki/engine/links.py

@@ -0,0 +1,25 @@
+"""Wikilink extraction — the kernel's link primitive (WikiEngineCoreArchitecture EC-4).
+
+`[[Target]]` and `[[Target|label]]`. CamelCase auto-linking is intentionally NOT here (it is an
+opt-in concern per FederationRequirements ADR-06); the kernel only knows explicit wikilinks.
+Link *resolution* (and red-link detection) is the kernel's job (it knows which keys exist);
+*rendering* is a consumer concern (headless engine, no UI).
+"""
+
+from __future__ import annotations
+
+import re
+
+__all__ = ["extract_wikilinks"]
+
+_WIKILINK = re.compile(r"\[\[([^\]|]+?)(?:\|[^\]]*)?\]\]")
+
+
+def extract_wikilinks(body: str) -> list[str]:
+    """Return the ordered, de-duplicated wikilink targets in ``body`` (label part dropped)."""
+    seen: dict[str, None] = {}
+    for m in _WIKILINK.finditer(body):
+        target = m.group(1).strip()
+        if target:
+            seen.setdefault(target, None)
+    return list(seen)

src/shard_wiki/engine/profile.py

@@ -0,0 +1,112 @@
+"""Capability profile derived from active extensions (WikiEngineCoreArchitecture E-5).
+
+The engine's §A `CapabilityProfile` is **computed**, not hand-set: start from the kernel base
+profile, then fold each active extension's `on_profile` contribution (in the runtime's
+deterministic order), then `validate()`. This realizes the chain *configuration (which
+extensions) → capability (the profile) → conformance* — activating an extension raises the
+shard's advertised capabilities, and composition can never yield an impossible profile (validate
+rejects it, §6.5).
+"""
+
+from __future__ import annotations
+
+import dataclasses
+from dataclasses import dataclass
+
+from shard_wiki.engine.extension import ActiveExtensions, Hook
+from shard_wiki.model import (
+    AccessGrant,
+    Addressing,
+    AttachmentMode,
+    CapabilityProfile,
+    ContentOpacity,
+    History,
+    MergeModel,
+    NativeQuery,
+    OperationalEnvelope,
+    Substrate,
+    Translation,
+    Verb,
+    WriteGranularity,
+)
+from shard_wiki.provenance import Liveness
+
+__all__ = ["engine_base_profile", "ProfileContribution", "derive_profile"]
+
+# Profile fields an extension may *raise* via on_profile (substrate/attachment are kernel-fixed).
+_OVERRIDABLE = (
+    "write_granularity",
+    "content_opacity",
+    "liveness",
+    "history",
+    "merge_model",
+    "addressing",
+    "native_query",
+    "translation",
+    "access_grant",
+)
+
+
+def engine_base_profile() -> CapabilityProfile:
+    """The kernel-only (no extensions) capability profile — the c2-minimum engine shard."""
+    return CapabilityProfile(
+        substrate=Substrate.FILES,
+        attachment_mode=AttachmentMode.IN_ENGINE_HOST,
+        write_granularity=WriteGranularity.PER_PAGE,
+        content_opacity=ContentOpacity.TRANSPARENT,
+        operational_envelope=OperationalEnvelope.LOCAL_UNBOUNDED,
+        access_grant=AccessGrant.OPEN,
+        liveness=Liveness.STATIC,
+        history=History.INTERNAL_ONLY,
+        merge_model=MergeModel.NONE,
+        addressing=Addressing.PATH,
+        native_query=NativeQuery.NONE,
+        translation=Translation.NATIVE,
+        supported_verbs=frozenset({Verb.READ, Verb.WRITE}),
+    ).validate()
+
+
+@dataclass(frozen=True, slots=True)
+class ProfileContribution:
+    """An extension's contribution to the derived profile (returned from its ON_PROFILE hook).
+
+    A non-``None`` axis overrides that axis; ``verbs_add`` are unioned in. Order = the runtime's
+    deterministic dispatch order, so later extensions win on a contested axis."""
+
+    write_granularity: WriteGranularity | None = None
+    content_opacity: ContentOpacity | None = None
+    liveness: Liveness | None = None
+    history: History | None = None
+    merge_model: MergeModel | None = None
+    addressing: Addressing | None = None
+    native_query: NativeQuery | None = None
+    translation: Translation | None = None
+    access_grant: AccessGrant | None = None
+    verbs_add: frozenset[Verb] = frozenset()
+
+
+def derive_profile(
+    active: ActiveExtensions, base: CapabilityProfile | None = None
+) -> CapabilityProfile:
+    """Fold active extensions' ON_PROFILE contributions onto ``base`` and validate the result.
+
+    Raises :class:`~shard_wiki.model.ProfileError` if the composed profile is impossible — so an
+    activation set can never advertise an invalid capability profile.
+    """
+    profile = base or engine_base_profile()
+    contributions = active.dispatch_collect(Hook.ON_PROFILE)
+
+    overrides: dict[str, object] = {}
+    verbs: set[Verb] = set(profile.supported_verbs)
+    for contrib in contributions:
+        if not isinstance(contrib, ProfileContribution):
+            continue
+        for field_name in _OVERRIDABLE:
+            value = getattr(contrib, field_name)
+            if value is not None:
+                overrides[field_name] = value
+        verbs |= set(contrib.verbs_add)
+
+    return dataclasses.replace(
+        profile, supported_verbs=frozenset(verbs), **overrides
+    ).validate()

src/shard_wiki/incremental/__init__.py

@@ -0,0 +1,46 @@
+"""incremental/ — the incremental-first derived tier (CoreArchitectureBlueprint §8.7).
+
+Equivalence is **indexed** (blocking/LSH + verify), not pairwise O(N²); maintenance is
+**change-driven** (delta with retraction + propagation, review B-4), keeping the derived tier equal
+to a from-scratch rebuild — which becomes a bounded fallback, not the operational path. A
+Merkle-style **digest** plus a background **consistency-checker** make ``derived = f(canonical)``
+verified rather than asserted (I-2), self-healing on detected drift.
+
+In-memory only for this slice (no persisted index store); per-partition structure is honoured but
+multi-tenant deployment is later. Per the dependency rule this imports down (model/provenance) and
+is wired by the orchestrator.
+"""
+
+from shard_wiki.incremental.equivalence import (
+    EquivalenceEdge,
+    EquivalenceIndex,
+    normalized_title,
+)
+from shard_wiki.incremental.minhash import (
+    MinHasher,
+    band_keys,
+    jaccard,
+    shingles,
+)
+from shard_wiki.incremental.union_index import UnionIndex
+from shard_wiki.incremental.verification import (
+    ConsistencyChecker,
+    ConsistencyReport,
+    derived_digest,
+    region_digest,
+)
+
+__all__ = [
+    "shingles",
+    "MinHasher",
+    "band_keys",
+    "jaccard",
+    "EquivalenceEdge",
+    "EquivalenceIndex",
+    "normalized_title",
+    "derived_digest",
+    "region_digest",
+    "ConsistencyReport",
+    "ConsistencyChecker",
+    "UnionIndex",
+]

src/shard_wiki/incremental/equivalence.py

@@ -0,0 +1,225 @@
+"""Indexed equivalence — blocking + verify, incrementally maintained (SHARD-WP-0011 T1/T2).
+
+Equivalence (two *distinct* identities holding the same page) is detected without pairwise O(N²):
+
+1. **Blocking** generates candidate pairs — pages sharing a normalized-title bucket or an LSH band
+   (MinHash over content shingles).
+2. **Verify** confirms a candidate — exact-body fingerprint match, or shingle Jaccard ≥ threshold —
+   plus **curator bindings** (explicit decision-log edges) which are always equivalence edges.
+
+The index is **incrementally maintained** (T2): ``add`` / ``update`` / ``remove`` re-bucket the
+changed page, **retract** the edges it leaves and **add** the edges it enters; equivalence groups
+are the connected components of the current edge set, so a retraction that disconnects a component
+**splits** a chorus automatically. A full :meth:`build` is just repeated ``add`` — the bounded
+rebuild fallback. The invariant (and the test oracle): incremental state == a from-scratch rebuild.
+"""
+
+from __future__ import annotations
+
+import hashlib
+import re
+from collections.abc import Iterable
+from dataclasses import dataclass
+
+from shard_wiki.incremental.minhash import MinHasher, band_keys, jaccard, shingles
+from shard_wiki.model import Identity, Page
+
+__all__ = ["EquivalenceEdge", "EquivalenceIndex", "normalized_title"]
+
+_NONALNUM_RE = re.compile(r"[^a-z0-9]+")
+
+
+def normalized_title(key: str) -> str:
+    """A blocking bucket key: the last path segment, lowercased, stripped of non-alphanumerics."""
+    leaf = key.rsplit("/", 1)[-1]
+    return _NONALNUM_RE.sub("", leaf.lower())
+
+
+@dataclass(frozen=True, slots=True)
+class EquivalenceEdge:
+    """A verified equivalence between two identities, tagged with why it was accepted."""
+
+    a: Identity
+    b: Identity
+    reason: str  # "fingerprint" | "content" | "curator"
+
+
+@dataclass(frozen=True, slots=True)
+class _Entry:
+    shingle_set: frozenset[str]
+    bands: tuple[tuple[int, tuple[int, ...]], ...]
+    title: str
+    fingerprint: str
+
+
+def _fingerprint(body: str) -> str:
+    return hashlib.blake2b(body.strip().encode("utf-8"), digest_size=16).hexdigest()
+
+
+def _pair(a: Identity, b: Identity) -> frozenset[Identity]:
+    return frozenset((a, b))
+
+
+class EquivalenceIndex:
+    """An incrementally maintained, blocked-and-verified equivalence relation over union pages."""
+
+    def __init__(
+        self,
+        *,
+        num_perm: int = 64,
+        num_bands: int = 32,
+        threshold: float = 0.7,
+        hasher: MinHasher | None = None,
+    ) -> None:
+        self.threshold = threshold
+        self.num_bands = num_bands
+        self._hasher = hasher or MinHasher(num_perm=num_perm)
+        self._entries: dict[Identity, _Entry] = {}
+        self._band_buckets: dict[tuple[int, tuple[int, ...]], set[Identity]] = {}
+        self._title_buckets: dict[str, set[Identity]] = {}
+        self._content_edges: dict[frozenset[Identity], str] = {}
+        self._curator_edges: set[frozenset[Identity]] = set()
+
+    # -- build / maintain ----------------------------------------------------
+
+    def build(
+        self,
+        pages: Iterable[Page],
+        curator_edges: Iterable[tuple[Identity, Identity]] = (),
+    ) -> None:
+        """Rebuild from scratch (the bounded fallback): add every page, then curator edges."""
+        self.__init__(
+            num_bands=self.num_bands, threshold=self.threshold, hasher=self._hasher
+        )
+        for page in pages:
+            self.add(page)
+        for a, b in curator_edges:
+            self.bind(a, b)
+
+    def add(self, page: Page) -> None:
+        """Index a new (or, via :meth:`update`, refreshed) page and add its equivalence edges."""
+        identity = page.identity
+        entry = self._make_entry(page)
+        self._entries[identity] = entry
+        for key in entry.bands:
+            self._band_buckets.setdefault(key, set()).add(identity)
+        self._title_buckets.setdefault(entry.title, set()).add(identity)
+
+        for candidate in self._candidates(identity, entry):
+            reason = self._verify(identity, candidate)
+            if reason is not None:
+                self._content_edges[_pair(identity, candidate)] = reason
+
+    def remove(self, identity: Identity) -> None:
+        """Drop a page: de-bucket it and retract every content edge incident to it."""
+        entry = self._entries.pop(identity, None)
+        if entry is None:
+            return
+        for key in entry.bands:
+            self._discard_bucket(self._band_buckets, key, identity)
+        self._discard_bucket(self._title_buckets, entry.title, identity)
+        for edge in [e for e in self._content_edges if identity in e]:
+            del self._content_edges[edge]
+
+    def update(self, page: Page) -> None:
+        """Apply a change as retract-then-add: stale (bucket-exit) edges go, new edges arrive."""
+        self.remove(page.identity)
+        self.add(page)
+
+    def bind(self, a: Identity, b: Identity) -> None:
+        """Record a curator equivalence (an explicit decision-log binding); always an edge."""
+        if a != b:
+            self._curator_edges.add(_pair(a, b))
+
+    def unbind(self, a: Identity, b: Identity) -> None:
+        self._curator_edges.discard(_pair(a, b))
+
+    def set_curator_edges(self, edges: Iterable[tuple[Identity, Identity]]) -> None:
+        """Replace all curator edges at once (re-syncing from the decision-log fold)."""
+        self._curator_edges = {_pair(a, b) for a, b in edges if a != b}
+
+    # -- queries -------------------------------------------------------------
+
+    def identities(self) -> frozenset[Identity]:
+        """All identities currently present in the index."""
+        return frozenset(self._entries)
+
+    def fingerprint(self, identity: Identity) -> str | None:
+        """The content fingerprint indexed for ``identity`` (None if absent) — a digest leaf."""
+        entry = self._entries.get(identity)
+        return entry.fingerprint if entry is not None else None
+
+    def edges(self) -> frozenset[frozenset[Identity]]:
+        """All equivalence edges (content + curator) among currently present identities."""
+        present = self._entries.keys()
+        curator = {e for e in self._curator_edges if e <= present}
+        return frozenset(set(self._content_edges) | curator)
+
+    def groups(self) -> tuple[frozenset[Identity], ...]:
+        """Equivalence groups: connected components of size ≥ 2 (union-find over the edges)."""
+        parent: dict[Identity, Identity] = {}
+
+        def find(x: Identity) -> Identity:
+            parent.setdefault(x, x)
+            root = x
+            while parent[root] != root:
+                root = parent[root]
+            while parent[x] != root:
+                parent[x], x = root, parent[x]
+            return root
+
+        for edge in self.edges():
+            a, b = tuple(edge)
+            ra, rb = find(a), find(b)
+            if ra != rb:
+                parent[ra] = rb
+
+        comps: dict[Identity, set[Identity]] = {}
+        for node in parent:
+            comps.setdefault(find(node), set()).add(node)
+        return tuple(
+            frozenset(members) for members in comps.values() if len(members) > 1
+        )
+
+    def equivalent_to(self, identity: Identity) -> frozenset[Identity]:
+        """The equivalence group containing ``identity`` (including itself), else just itself."""
+        for group in self.groups():
+            if identity in group:
+                return group
+        return frozenset({identity})
+
+    # -- internals -----------------------------------------------------------
+
+    def _make_entry(self, page: Page) -> _Entry:
+        shingle_set = shingles(page.body)
+        signature = self._hasher.signature(shingle_set)
+        return _Entry(
+            shingle_set=shingle_set,
+            bands=band_keys(signature, self.num_bands),
+            title=normalized_title(page.identity.key),
+            fingerprint=_fingerprint(page.body),
+        )
+
+    def _candidates(self, identity: Identity, entry: _Entry) -> set[Identity]:
+        candidates: set[Identity] = set()
+        for key in entry.bands:
+            candidates |= self._band_buckets.get(key, set())
+        candidates |= self._title_buckets.get(entry.title, set())
+        candidates.discard(identity)
+        return candidates
+
+    def _verify(self, a: Identity, b: Identity) -> str | None:
+        ea, eb = self._entries[a], self._entries[b]
+        if ea.fingerprint == eb.fingerprint:
+            return "fingerprint"
+        if jaccard(ea.shingle_set, eb.shingle_set) >= self.threshold:
+            return "content"
+        return None
+
+    @staticmethod
+    def _discard_bucket(buckets: dict, key, identity: Identity) -> None:
+        bucket = buckets.get(key)
+        if bucket is not None:
+            bucket.discard(identity)
+            if not bucket:
+                del buckets[key]

src/shard_wiki/incremental/minhash.py

@@ -0,0 +1,71 @@
+"""MinHash + LSH banding primitives for content-similarity blocking (SHARD-WP-0011 T1).
+
+Pure, deterministic functions (fixed hashing, no per-run randomness) so the derived tier and its
+digest are reproducible. Shingle a body into k-grams, MinHash the shingle set into a signature,
+split the signature into LSH bands; two pages sharing a band are *candidates* for equivalence —
+the cheap pre-filter that replaces pairwise O(N²) comparison.
+"""
+
+from __future__ import annotations
+
+import hashlib
+import random
+import re
+from collections.abc import Iterable
+
+__all__ = ["shingles", "MinHasher", "band_keys", "jaccard"]
+
+_WORD_RE = re.compile(r"\w+")
+# Largest Mersenne prime below 2**61 — the modulus for the universal-hash permutations.
+_PRIME = (1 << 61) - 1
+
+
+def shingles(text: str, k: int = 3) -> frozenset[str]:
+    """The set of word k-grams in ``text`` (lowercased). Short texts fall back to their word set."""
+    words = _WORD_RE.findall(text.lower())
+    if len(words) < k:
+        return frozenset(words)
+    return frozenset(" ".join(words[i : i + k]) for i in range(len(words) - k + 1))
+
+
+def _stable_hash(token: str) -> int:
+    return int.from_bytes(hashlib.blake2b(token.encode("utf-8"), digest_size=8).digest(), "big")
+
+
+class MinHasher:
+    """A bank of ``num_perm`` universal hash permutations producing a fixed-length signature."""
+
+    def __init__(self, num_perm: int = 64, seed: int = 1) -> None:
+        self.num_perm = num_perm
+        rng = random.Random(seed)
+        self._coeffs = [
+            (rng.randrange(1, _PRIME), rng.randrange(0, _PRIME)) for _ in range(num_perm)
+        ]
+
+    def signature(self, shingle_set: Iterable[str]) -> tuple[int, ...]:
+        """The MinHash signature of ``shingle_set`` (empty set → all-``_PRIME`` sentinel)."""
+        hashed = [_stable_hash(s) for s in shingle_set]
+        if not hashed:
+            return tuple(_PRIME for _ in self._coeffs)
+        return tuple(min((a * h + b) % _PRIME for h in hashed) for a, b in self._coeffs)
+
+
+def band_keys(
+    signature: tuple[int, ...], num_bands: int
+) -> tuple[tuple[int, tuple[int, ...]], ...]:
+    """Split a signature into ``num_bands`` band keys; two pages sharing one are LSH candidates."""
+    if num_bands <= 0 or len(signature) % num_bands != 0:
+        raise ValueError(f"signature length {len(signature)} not divisible into {num_bands} bands")
+    rows = len(signature) // num_bands
+    return tuple(
+        (b, signature[b * rows : (b + 1) * rows]) for b in range(num_bands)
+    )
+
+
+def jaccard(a: frozenset[str], b: frozenset[str]) -> float:
+    """Jaccard similarity of two shingle sets; two empty sets are defined as identical (1.0)."""
+    if not a and not b:
+        return 1.0
+    if not a or not b:
+        return 0.0
+    return len(a & b) / len(a | b)

src/shard_wiki/incremental/union_index.py

@@ -0,0 +1,91 @@
+"""UnionIndex — the maintained derived tier wired behind resolution + views (SHARD-WP-0011 T4).
+
+Wraps a :class:`UnionGraph` + decision log with an incrementally maintained
+:class:`EquivalenceIndex`. Content equivalence is kept fresh by deltas (``note_change`` /
+``note_removed``); curator bindings are re-synced live from the log fold. A full :meth:`rebuild`
+is the bounded fallback. :meth:`verify` runs the I-2 consistency-checker over the live source.
+
+Consumer-visible results are unchanged — equivalence groups are exposed in the same string form the
+decision-log fold uses, a *superset* that additionally collapses genuine content duplicates — only
+freshness and cost differ (recompute-on-read becomes change-driven).
+"""
+
+from __future__ import annotations
+
+from shard_wiki.coordination import DecisionLog
+from shard_wiki.incremental.equivalence import EquivalenceIndex
+from shard_wiki.incremental.verification import (
+    ConsistencyChecker,
+    ConsistencyReport,
+    derived_digest,
+)
+from shard_wiki.model import Identity, Page
+from shard_wiki.union import UnionGraph
+
+__all__ = ["UnionIndex"]
+
+
+def _identity(token: str) -> Identity:
+    shard, _, key = token.partition(":")
+    return Identity(shard, key)
+
+
+class UnionIndex:
+    """An incrementally maintained equivalence index over a union, with a rebuild fallback."""
+
+    def __init__(self, union: UnionGraph, log: DecisionLog, space: str) -> None:
+        self._union = union
+        self._log = log
+        self._space = space
+        self._eq = EquivalenceIndex()
+        self.rebuild()
+
+    def rebuild(self) -> None:
+        """The bounded fallback: re-derive the whole index from current union pages + bindings."""
+        self._eq.build(self._union.iter_pages())
+        self._sync_curator()
+
+    def note_change(self, page: Page) -> None:
+        """Change-driven update for one added/edited page (the operational path)."""
+        self._eq.update(page)
+
+    def note_removed(self, identity: Identity) -> None:
+        self._eq.remove(identity)
+
+    def _sync_curator(self) -> None:
+        """Re-sync curator equivalence from the live decision-log fold (cheap, always correct)."""
+        groups = self._log.fold(self._space).equivalence_groups
+        edges: list[tuple[Identity, Identity]] = []
+        for group in groups:
+            members = [_identity(m) for m in group]
+            edges.extend((members[0], other) for other in members[1:])
+        self._eq.set_curator_edges(edges)
+
+    def equivalence_groups(self) -> tuple[frozenset[str], ...]:
+        """Equivalence groups in decision-log string form (curator ∪ content), for the views."""
+        self._sync_curator()
+        return tuple(
+            frozenset(str(identity) for identity in group) for group in self._eq.groups()
+        )
+
+    def digest(self) -> str:
+        """The Merkle-style digest of the maintained derived tier (I-2)."""
+        self._sync_curator()
+        return derived_digest(self._eq)
+
+    def verify(self) -> ConsistencyReport:
+        """Check the maintained index against a from-scratch fold of the live source; self-heal."""
+        self._sync_curator()
+        checker = ConsistencyChecker(
+            self._eq,
+            pages=lambda: list(self._union.iter_pages()),
+            curator_edges=self._curator_pairs,
+        )
+        return checker.check_and_repair()
+
+    def _curator_pairs(self) -> list[tuple[Identity, Identity]]:
+        pairs: list[tuple[Identity, Identity]] = []
+        for group in self._log.fold(self._space).equivalence_groups:
+            members = [_identity(m) for m in group]
+            pairs.extend((members[0], other) for other in members[1:])
+        return pairs

src/shard_wiki/incremental/verification.py

@@ -0,0 +1,112 @@
+"""I-2 verification — digest + background consistency-checker (SHARD-WP-0011 T3).
+
+``derived = f(canonical)`` is made *verified*, not asserted. A **Merkle-style digest** summarizes
+the derived tier (each identity's content fingerprint + its incident equivalence edges as a leaf,
+order-independently combined into a root) so two derived states are equal iff their digests match.
+A **consistency-checker** recomputes the authoritative fold from the current source, compares it to
+the maintained index over a (sampled) region, and on mismatch performs a **scoped recompute** of
+just the affected identities — self-healing drift from a missed delta or corrupted state.
+
+The digest is a pure function of index state, so it is "maintained alongside deltas" for free and
+is stable under equivalent event orders (leaves are sorted before combination).
+"""
+
+from __future__ import annotations
+
+import hashlib
+from collections.abc import Callable, Iterable
+from dataclasses import dataclass
+
+from shard_wiki.incremental.equivalence import EquivalenceIndex
+from shard_wiki.model import Identity, Page
+
+__all__ = ["region_digest", "derived_digest", "ConsistencyReport", "ConsistencyChecker"]
+
+CuratorEdges = Iterable[tuple[Identity, Identity]]
+
+
+def _leaf(index: EquivalenceIndex, identity: Identity) -> str:
+    """A digest leaf for one identity: its fingerprint + its incident edges (as sorted peers)."""
+    fingerprint = index.fingerprint(identity) or "∅"
+    peers = sorted(
+        str(other)
+        for edge in index.edges()
+        if identity in edge
+        for other in edge
+        if other != identity
+    )
+    payload = f"{identity}|{fingerprint}|{','.join(peers)}"
+    return hashlib.blake2b(payload.encode("utf-8"), digest_size=16).hexdigest()
+
+
+def region_digest(index: EquivalenceIndex, identities: Iterable[Identity]) -> str:
+    """A Merkle-style root over the given identities' leaves (order-independent)."""
+    leaves = sorted(_leaf(index, identity) for identity in identities)
+    root = hashlib.blake2b(digest_size=16)
+    for leaf in leaves:
+        root.update(leaf.encode("utf-8"))
+    return root.hexdigest()
+
+
+def derived_digest(index: EquivalenceIndex) -> str:
+    """The digest of the whole maintained derived tier."""
+    return region_digest(index, index.identities())
+
+
+@dataclass(frozen=True, slots=True)
+class ConsistencyReport:
+    """Outcome of a consistency check: what was examined, whether it drifted, and if it healed."""
+
+    checked: int
+    drifted: bool
+    repaired: bool
+    healthy: bool
+
+
+class ConsistencyChecker:
+    """Compares the maintained index against an authoritative rebuild and repairs drift in place."""
+
+    def __init__(
+        self,
+        index: EquivalenceIndex,
+        pages: Callable[[], Iterable[Page]],
+        curator_edges: Callable[[], CuratorEdges] = lambda: (),
+    ) -> None:
+        self._index = index
+        self._pages = pages
+        self._curator = curator_edges
+
+    def _authoritative(self) -> EquivalenceIndex:
+        expected = EquivalenceIndex(
+            num_bands=self._index.num_bands, threshold=self._index.threshold
+        )
+        expected.build(list(self._pages()), list(self._curator()))
+        return expected
+
+    def check_and_repair(self, sample: Iterable[Identity] | None = None) -> ConsistencyReport:
+        """Verify the (sampled) region against a from-scratch fold; scoped-recompute on mismatch."""
+        source = {p.identity: p for p in self._pages()}
+        expected = self._authoritative()
+        region = (
+            set(sample)
+            if sample is not None
+            else set(source) | set(self._index.identities())
+        )
+
+        drifted = region_digest(self._index, region) != region_digest(expected, region)
+        if not drifted:
+            return ConsistencyReport(len(region), drifted=False, repaired=False, healthy=True)
+
+        self._repair(region, source)
+        healthy = region_digest(self._index, region) == region_digest(expected, region)
+        return ConsistencyReport(len(region), drifted=True, repaired=True, healthy=healthy)
+
+    def _repair(self, region: set[Identity], source: dict[Identity, Page]) -> None:
+        """Scoped recompute: reconcile each affected identity to the current source."""
+        present = self._index.identities()
+        for identity in region:
+            page = source.get(identity)
+            if page is not None:
+                self._index.update(page) if identity in present else self._index.add(page)
+            elif identity in present:
+                self._index.remove(identity)

src/shard_wiki/model/__init__.py

@@ -0,0 +1,47 @@
+"""model/ — the backend-neutral page model and capability types (the top waist).
+
+Imports only the ``provenance`` leaf; nothing backend-specific lives here.
+"""
+
+from shard_wiki.model.capability import (
+    AccessGrant,
+    Addressing,
+    AttachmentMode,
+    CapabilityProfile,
+    ContentOpacity,
+    History,
+    MergeModel,
+    NativeQuery,
+    NotSupported,
+    OperationalEnvelope,
+    ProfileError,
+    Substrate,
+    Translation,
+    Verb,
+    WriteGranularity,
+)
+from shard_wiki.model.identity import Identity, Placement, Span
+from shard_wiki.model.page import Page, PageShape
+
+__all__ = [
+    "Identity",
+    "Placement",
+    "Span",
+    "Page",
+    "PageShape",
+    "CapabilityProfile",
+    "Verb",
+    "Substrate",
+    "AttachmentMode",
+    "WriteGranularity",
+    "ContentOpacity",
+    "OperationalEnvelope",
+    "AccessGrant",
+    "History",
+    "MergeModel",
+    "Addressing",
+    "NativeQuery",
+    "Translation",
+    "ProfileError",
+    "NotSupported",
+]

src/shard_wiki/model/capability.py

@@ -0,0 +1,220 @@
+"""Capability profile — capability-as-data (CoreArchitectureBlueprint §6, I-3).
+
+A binding's abilities are a *position on each capability spectrum*, not a boolean checklist.
+Descriptively there are fifteen spectra (§6.1); operationally they reduce to a small
+**orthogonal core** plus **implied** axes, with **implication rules that forbid impossible
+profiles** (§6.5). ``CapabilityProfile.validate()`` enforces those rules; a profile that
+violates one is rejected (the structural half of "capability-as-data is sound" — the behavioural
+half is the conformance suite, T4).
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from enum import Enum
+
+from shard_wiki.provenance import Liveness
+
+__all__ = [
+    "Verb",
+    "Substrate",
+    "AttachmentMode",
+    "WriteGranularity",
+    "ContentOpacity",
+    "OperationalEnvelope",
+    "AccessGrant",
+    "History",
+    "MergeModel",
+    "Addressing",
+    "NativeQuery",
+    "Translation",
+    "CapabilityProfile",
+    "ProfileError",
+    "NotSupported",
+]
+
+CONTRACT_VERSION = "0.1"
+
+
+class ProfileError(ValueError):
+    """Raised when a capability profile is internally impossible (violates §6.5 rules)."""
+
+
+class NotSupported(Exception):
+    """Raised by an adapter when an operation verb is not in its capability profile."""
+
+
+class Verb(Enum):
+    READ = "read"
+    WRITE = "write"
+    DIFF = "diff"
+    MERGE = "merge"
+    LOCK = "lock"
+    VERSION = "version"
+    PUBLISH = "publish"
+    NOTIFY = "notify"
+    TRANSCLUDE_SOURCE = "transclude-source"
+    TRANSLATE_SYNTAX = "translate-syntax"
+    STRUCTURED_PAYLOAD = "structured-payload"
+    DERIVE_PROJECTION = "derive-projection"  # gated, off by default (T18)
+    EXECUTE = "execute"  # gated, off by default (T18)
+
+
+# --- orthogonal core axes (§6.5a) ---
+class Substrate(Enum):
+    GIT = "git"
+    FILES = "files"
+    RELATIONAL_DB = "relational-db"
+    EXTERNAL_API = "external-api"
+    CRDT = "crdt"
+
+
+class WriteGranularity(Enum):
+    NONE = "none"  # read-only
+    WHOLE_FILE = "whole-file"
+    SECTION = "section"
+    PER_PAGE = "per-page"
+    PER_BLOCK = "per-block"
+
+
+class ContentOpacity(Enum):
+    TRANSPARENT = "transparent"
+    STRUCTURED_REEVALUABLE = "structured-re-evaluable"
+    ENCRYPTED = "encrypted"
+    PER_ITEM = "per-item"
+    PROPRIETARY_LOSSY = "proprietary-lossy"
+
+
+class OperationalEnvelope(Enum):
+    LOCAL_UNBOUNDED = "local-unbounded"
+    REALTIME = "realtime"
+    RATE_LIMITED = "rate-limited"
+
+
+class AccessGrant(Enum):
+    OPEN = "open"
+    TOKEN = "token"
+    OAUTH_SCOPED = "oauth-scoped"
+    P2P_KEY = "p2p-key"
+    ENTERPRISE_ACL = "enterprise-acl"
+
+
+# --- implied axes (§6.5b): may be derived from the core, validated for consistency ---
+class History(Enum):
+    NONE = "none"
+    INTERNAL_ONLY = "internal-only"
+    CRDT_LOG = "crdt-log"
+    OPEN_FILE = "open-file"
+    GIT_NATIVE = "git-native"
+
+
+class MergeModel(Enum):
+    NONE = "none"
+    GIT_TEXT = "git-text"
+    KEEP_BOTH = "keep-both"
+    NATIVE_CRDT = "native-crdt"
+    COEXIST_RANK = "coexist-rank"
+
+
+class AttachmentMode(Enum):
+    # NB: there is deliberately no IMAGE mode — an image/live-memory blob is never an attach
+    # target (I-12). It participates only via export→files.
+    FILE_STORE = "file-store"
+    GIT_IS_STORE = "git-is-store"
+    IN_ENGINE_HOST = "in-engine-host"
+    LOCAL_REST = "local-rest"
+    EXTERNAL_API = "external-api"
+    DIRECT_DB = "direct-db"
+    CRDT_REPLICA = "crdt-replica"
+    P2P = "p2p"
+
+
+class Addressing(Enum):
+    NONE = "none"
+    PATH = "path"
+    PAGE_ID = "page-id"
+    SPAN = "span"
+    BLOCK_ID = "block-id"
+    STORE_UUID = "store-uuid"
+    TUMBLER = "tumbler"
+
+
+class NativeQuery(Enum):
+    NONE = "none"
+    TEXT = "text"
+    DERIVED_INDEX = "derived-index"
+    DATALOG_GRAPH = "datalog-graph"
+    DB_QUERY = "db-query"
+    SPARQL = "sparql"
+
+
+class Translation(Enum):
+    NATIVE = "native"
+    LOSSLESS = "lossless"
+    LOSSY_WITH_REPORT = "lossy-with-report"
+
+
+@dataclass(frozen=True, slots=True)
+class CapabilityProfile:
+    """A verified-at-registration position on each capability axis, plus supported verbs."""
+
+    # orthogonal core
+    substrate: Substrate
+    attachment_mode: AttachmentMode
+    write_granularity: WriteGranularity
+    content_opacity: ContentOpacity
+    operational_envelope: OperationalEnvelope
+    access_grant: AccessGrant
+    liveness: Liveness  # computational/liveness axis (15th)
+    # implied
+    history: History
+    merge_model: MergeModel
+    addressing: Addressing
+    native_query: NativeQuery
+    translation: Translation
+    supported_verbs: frozenset[Verb] = field(default_factory=frozenset)
+    contract_version: str = CONTRACT_VERSION
+
+    def supports(self, verb: Verb) -> bool:
+        return verb in self.supported_verbs
+
+    def validate(self) -> CapabilityProfile:
+        """Apply the §6.5 implication rules; raise :class:`ProfileError` on an impossible
+        combination. Returns ``self`` so it can be used fluently at construction."""
+        rules: list[tuple[bool, str]] = [
+            (
+                Verb.READ in self.supported_verbs,
+                "every shard must support READ (the capability floor)",
+            ),
+            (
+                self.attachment_mode is not AttachmentMode.GIT_IS_STORE
+                or (self.substrate is Substrate.GIT and self.history is History.GIT_NATIVE),
+                "git-is-store ⟹ substrate=git ∧ history=git-native",
+            ),
+            (
+                self.content_opacity is not ContentOpacity.ENCRYPTED
+                or self.native_query is NativeQuery.NONE,
+                "encrypted opacity ⟹ native-query=none",
+            ),
+            (
+                self.merge_model is not MergeModel.NATIVE_CRDT
+                or (
+                    self.history is History.CRDT_LOG
+                    and self.operational_envelope is OperationalEnvelope.REALTIME
+                ),
+                "native-crdt merge ⟹ history=crdt-log ∧ envelope=realtime",
+            ),
+            (
+                (self.write_granularity is WriteGranularity.NONE)
+                == (Verb.WRITE not in self.supported_verbs),
+                "write-granularity=none ⟺ WRITE not supported (read-only consistency)",
+            ),
+            (
+                Verb.MERGE not in self.supported_verbs or self.merge_model is not MergeModel.NONE,
+                "MERGE verb ⟹ merge-model ≠ none",
+            ),
+        ]
+        broken = [msg for ok, msg in rules if not ok]
+        if broken:
+            raise ProfileError("; ".join(broken))
+        return self

src/shard_wiki/model/identity.py

@@ -0,0 +1,60 @@
+"""Identity, Placement, Span — three distinct concepts (CoreArchitectureBlueprint §7.2).
+
+- **Identity** is a *stable handle* assigned/minted by a shard; it survives edits. It is NEVER
+  derived from content (a content fingerprint identifies a *version*, not a *page*).
+- **Placement** is *where* an identity sits (path in a shard); one identity may have many
+  placements (a DAG). Placement can change without changing identity.
+- **Span** is a sub-page address within an identity, optionally carrying a provenance delta.
+
+Equivalence (detecting that two *distinct* identities hold the same content) is a separate
+mechanism and lives in ``union/`` — not here.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+from shard_wiki.provenance import SpanProvenanceDelta
+
+__all__ = ["Identity", "Placement", "Span"]
+
+
+@dataclass(frozen=True, slots=True)
+class Identity:
+    """A shard-scoped, stable page handle. Value-equal; stable across content edits.
+
+    ``shard`` scopes the handle so native ids survive projection and never collide across
+    shards. ``key`` is the backend's stable handle (page name / native uid) — not a fingerprint.
+    """
+
+    shard: str
+    key: str
+
+    def __str__(self) -> str:
+        return f"{self.shard}:{self.key}"
+
+
+@dataclass(frozen=True, slots=True)
+class Placement:
+    """Where an identity sits: a path within a shard. Mutable over an identity's life."""
+
+    shard: str
+    path: str
+
+    def __str__(self) -> str:
+        return f"{self.shard}/{self.path}"
+
+
+@dataclass(frozen=True, slots=True)
+class Span:
+    """A sub-page address within a page identity, with an optional provenance delta.
+
+    ``ref`` is a native span id where the backend mints one (Roam ``:block/uid``, Logseq
+    ``id::``), else a positional/fingerprint address. ``delta`` overrides the page envelope
+    only where this span genuinely differs (effective-vs-own, blueprint §7.3).
+    """
+
+    ref: str
+    start: int | None = None
+    end: int | None = None
+    delta: SpanProvenanceDelta | None = None

src/shard_wiki/model/page.py

@@ -0,0 +1,43 @@
+"""The backend-neutral wiki page model — the top narrow waist (CoreArchitectureBlueprint §7).
+
+Markdown-first but stretchable: every shape reduces to
+``(content|source, structure, provenance envelope, [derivation rule])``.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from enum import Enum
+
+from shard_wiki.model.identity import Identity, Placement, Span
+from shard_wiki.provenance import ProvenanceEnvelope
+
+__all__ = ["PageShape", "Page"]
+
+
+class PageShape(Enum):
+    """The page-model shapes (blueprint §7.1). The slice handles PROSE; the rest are declared
+    so adapters can tag content faithfully (union without erasure)."""
+
+    PROSE = "prose"
+    TYPED_RECORD = "typed-record"
+    TYPED_GRAPH = "typed-graph"
+    INLINE_EMBEDDED = "inline-embedded"
+    NON_MARKDOWN_ASSET = "non-markdown-asset"
+    ONE_SOURCE_MANY_PROJECTIONS = "one-source-many-projections"
+    NOTEBOOK = "notebook"
+    PROGRAM_AS_PAGE = "program-as-page"
+    LIVE_TEMPORAL = "live-temporal"
+
+
+@dataclass(frozen=True, slots=True)
+class Page:
+    """A page in the union: a stable identity, content, the page-level provenance envelope,
+    its placements, and its spans (whose deltas layer over the page envelope, §7.3)."""
+
+    identity: Identity
+    body: str
+    envelope: ProvenanceEnvelope
+    shape: PageShape = PageShape.PROSE
+    placements: tuple[Placement, ...] = ()
+    spans: tuple[Span, ...] = field(default_factory=tuple)

src/shard_wiki/policy/__init__.py

@@ -0,0 +1,39 @@
+"""policy/ — the configurable policy surface, a dependency-free leaf (blueprint §10, §11).
+
+Mechanism over policy (I-7): core mechanisms read policy *choices* from here; they never
+hard-code one. This leaf holds only the presets + a pure ``resolve``-style selector. Mechanism
+(how a choice is honoured) lives in ``coordination``/``union``/``projection``, never here.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from enum import Enum
+
+__all__ = ["CanonicalSource", "Policy", "DEFAULT_POLICY"]
+
+
+class CanonicalSource(Enum):
+    """Resolution policy over a divergent/equivalent set (FederationArchitecture T9). Detection
+    is core; this is only the *resolution* choice."""
+
+    CHORUS = "chorus"  # default: present all versions, none privileged
+    DESIGNATED_CANONICAL = "designated-canonical"
+    GIT_MERGE = "git-merge"
+    VOTE = "vote"
+    OVERLAY_ONLY = "overlay-only"
+
+
+@dataclass(frozen=True, slots=True)
+class Policy:
+    """A space's policy choices. Extended as the policy surface grows (freshness, compaction,
+    execution, tenant mapping — blueprint §10); the slice needs canonical-source + designation."""
+
+    canonical_source: CanonicalSource = CanonicalSource.CHORUS
+    designated_shard: str | None = None
+    # Whether an unapplied overlay's body is projected over its canonical page on read. Either
+    # way the overlay is never *hidden* — overlay_state is always surfaced in provenance.
+    show_drafts: bool = True
+
+
+DEFAULT_POLICY = Policy()

src/shard_wiki/provenance/__init__.py

@@ -0,0 +1,116 @@
+"""Provenance — the cross-cutting leaf rail (CoreArchitectureBlueprint §7.3, §11).
+
+Every artifact in the union carries a :class:`ProvenanceEnvelope`. To keep per-span cost near
+zero when provenance is uniform, envelopes are **layered**: a page-level envelope plus optional
+per-span deltas. The *effective* provenance of a span is ``page_envelope ⊕ span_delta`` — a span
+with no delta inherits the page envelope at zero cost ("effective-vs-own", the same pattern the
+page model uses for computed metadata).
+
+This module is a **dependency-free leaf**: it imports nothing else in the package and contains
+only stable data types plus the pure ``effective`` composition. Mechanism never lives here.
+"""
+
+from __future__ import annotations
+
+import dataclasses
+from dataclasses import dataclass
+from datetime import datetime
+from enum import Enum
+
+__all__ = [
+    "Liveness",
+    "Staleness",
+    "OverlayState",
+    "ProvenanceEnvelope",
+    "SpanProvenanceDelta",
+    "effective",
+]
+
+
+class Liveness(Enum):
+    """Where a view sits on the live↔snapshot axis (blueprint §8, T18)."""
+
+    STATIC = "static"
+    CAPTURED_SNAPSHOT = "captured-snapshot"
+    LIVE_OVER_FILES = "live-over-files"
+    VIEW_TIME = "view-time"
+    IRREDUCIBLY_LIVE = "irreducibly-live"
+
+
+class Staleness(Enum):
+    """Freshness state of cached/projected content (blueprint §8.8). ``UNAVAILABLE`` is the
+    dead-shard state (FederationRequirements ADR-04)."""
+
+    LIVE = "live"
+    FRESH = "fresh"
+    STALE = "stale"
+    UNAVAILABLE = "unavailable"
+
+
+class OverlayState(Enum):
+    """Overlay lifecycle state of an artifact (FederationRequirements ADR-05)."""
+
+    NONE = "none"
+    DRAFT = "draft"
+    PATCH_PENDING = "patch-pending"
+    APPLIED = "applied"
+
+
+@dataclass(frozen=True, slots=True)
+class ProvenanceEnvelope:
+    """The metadata every page/span carries — union without erasure (INTENT I-4).
+
+    This is the *page-level* (or fully-resolved *effective*) form. Per-span overrides are
+    expressed as a :class:`SpanProvenanceDelta` and composed via :func:`effective`.
+    """
+
+    source_shard: str
+    liveness: Liveness = Liveness.STATIC
+    staleness: Staleness = Staleness.FRESH
+    overlay_state: OverlayState = OverlayState.NONE
+    source_rev: str | None = None
+    observed_at: datetime | None = None
+    authz_context: str | None = None
+    divergence: tuple[str, ...] = ()
+    lineage: str | None = None
+
+
+@dataclass(frozen=True, slots=True)
+class SpanProvenanceDelta:
+    """A per-span override of a page envelope. Every field is optional; ``None`` (or, for
+    ``divergence``, the sentinel default) means *inherit the page-level value*. A span with an
+    all-default delta — or no delta at all — costs nothing and resolves to the page envelope.
+    """
+
+    source_shard: str | None = None
+    liveness: Liveness | None = None
+    staleness: Staleness | None = None
+    overlay_state: OverlayState | None = None
+    source_rev: str | None = None
+    observed_at: datetime | None = None
+    authz_context: str | None = None
+    # Sentinel: ``None`` means inherit; an explicit (possibly empty) tuple overrides.
+    divergence: tuple[str, ...] | None = None
+    lineage: str | None = None
+
+    def is_empty(self) -> bool:
+        """True when the delta overrides nothing (the common, zero-cost case)."""
+        return all(getattr(self, f.name) is None for f in dataclasses.fields(self))
+
+
+def effective(
+    base: ProvenanceEnvelope, delta: SpanProvenanceDelta | None = None
+) -> ProvenanceEnvelope:
+    """Compose a page envelope with an optional span delta → the span's effective provenance.
+
+    ``effective(base, None)`` and ``effective(base, <empty delta>)`` both return ``base``
+    unchanged (zero-cost inheritance). Any non-``None`` delta field overrides ``base``.
+    """
+    if delta is None or delta.is_empty():
+        return base
+    overrides = {
+        f.name: value
+        for f in dataclasses.fields(delta)
+        if (value := getattr(delta, f.name)) is not None
+    }
+    return dataclasses.replace(base, **overrides)

src/shard_wiki/space.py

@@ -0,0 +1,148 @@
+"""InformationSpace — the thin orchestrator entry tying the slice together (blueprint §3 L6).
+
+A root entity / information space: shards attach to it (conformance-gated, TSD §A.2), a
+coordination decision log records its canonical decisions, and a derived union resolves names to
+pages. This is the L6 consumer surface for the foundation slice (attach → resolve → read);
+a network API is a later workplan.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from shard_wiki.adapters import ShardAdapter, assert_conformant
+from shard_wiki.coordination import (
+    ApplyResult,
+    DecisionLog,
+    EventStore,
+    EventType,
+    GitEventStore,
+    Overlay,
+    OverlayEngine,
+)
+from shard_wiki.incremental import ConsistencyReport, UnionIndex
+from shard_wiki.model import Page
+from shard_wiki.policy import DEFAULT_POLICY, Policy
+from shard_wiki.union import Resolution, UnionGraph
+from shard_wiki.views import (
+    AllPagesEntry,
+    BackLink,
+    ChangeEntry,
+    SiteMapNode,
+    all_pages,
+    build_backlinks,
+    recent_changes,
+    site_map,
+)
+
+__all__ = ["InformationSpace"]
+
+
+class InformationSpace:
+    def __init__(
+        self,
+        space_id: str,
+        policy: Policy = DEFAULT_POLICY,
+        *,
+        store: EventStore | None = None,
+    ) -> None:
+        """Tie the slice together. ``store`` selects the coordination-log backend: the default
+        in-memory store (tests) or a git-addressable one. Use :meth:`git_backed` for the latter."""
+        self.space_id = space_id
+        self.log = DecisionLog(store)
+        self.union = UnionGraph(space_id, log=self.log, policy=policy)
+        self.overlays = OverlayEngine(space_id, self.log)
+        self._index: UnionIndex | None = None  # maintained derived tier, built lazily
+        self._index_stale = True
+
+    @classmethod
+    def git_backed(
+        cls,
+        space_id: str,
+        repo_path: str | Path,
+        policy: Policy = DEFAULT_POLICY,
+    ) -> InformationSpace:
+        """An information space whose coordination log is git-addressable (history/patch/review/
+        backup — I-6). The decision log lives in the git repo at ``repo_path``."""
+        return cls(space_id, policy, store=GitEventStore(repo_path))
+
+    def attach(self, adapter: ShardAdapter) -> None:
+        """Attach a shard — only if it passes conformance (verified profile, I-3/§6.6)."""
+        assert_conformant(adapter)
+        self.union.attach(adapter)
+        self._index_stale = True
+
+    def alias(self, name: str, target: str, actor: str | None = None) -> None:
+        """Record a coordination-canonical alias (``name`` → ``"shard:key"``) in the log."""
+        self.log.append(
+            self.space_id, EventType.ALIAS_SET, {"alias": name, "target": target}, actor=actor
+        )
+
+    def resolve(self, name: str) -> Resolution:
+        return self.union.resolve(name)
+
+    def read(self, name: str) -> Page:
+        """Resolve and return the page (or the canonical pick of a chorus). KeyError if red-link."""
+        return self.union.resolve(name).single()
+
+    def overlay(self, name: str, body: str, actor: str | None = None) -> Overlay:
+        """Draft a non-destructive overlay against the resolved page (overlay-before-mutation)."""
+        page = self.read(name)
+        return self.overlays.draft(page.identity, body, page.envelope.source_rev, actor=actor)
+
+    def apply_overlay(self, overlay_id: str) -> ApplyResult:
+        """Apply a draft overlay to its target shard (apply-under-drift, §8.6)."""
+        overlay = self.overlays.get(overlay_id)
+        if overlay is None:
+            raise KeyError(overlay_id)
+        adapter = self.union.shard(overlay.target.shard)
+        if adapter is None:
+            raise KeyError(overlay.target.shard)
+        return self.overlays.apply(overlay_id, adapter)
+
+    def edit(self, name: str, body: str, actor: str | None = None) -> ApplyResult:
+        """Edit a page through the one principled path: draft an overlay, then apply it. A
+        write-through-capable target fast-forwards (write-through); a read-only target keeps the
+        draft as local truth (I-5: overlay before mutation, always)."""
+        overlay = self.overlay(name, body, actor=actor)
+        result = self.apply_overlay(overlay.overlay_id)
+        self._index_stale = True  # the applied edit changes the derived tier
+        return result
+
+    # --- maintained derived tier (SHARD-WP-0011): incremental-first, rebuild as fallback ---
+
+    @property
+    def index(self) -> UnionIndex:
+        """The maintained equivalence index (built lazily; rebuilt when the union has changed)."""
+        if self._index is None:
+            self._index = UnionIndex(self.union, self.log, self.space_id)
+        elif self._index_stale:
+            self._index.rebuild()  # bounded fallback after a mutation
+        self._index_stale = False
+        return self._index
+
+    def reindex(self) -> None:
+        """Force a full rebuild of the maintained derived tier (the explicit fallback path)."""
+        self.index.rebuild()
+
+    def verify_index(self) -> ConsistencyReport:
+        """Run the I-2 consistency-checker over the maintained tier; self-heal any drift."""
+        return self.index.verify()
+
+    # --- derived views (SHARD-WP-0010): recomputable, provenance-carrying, presentation-free ---
+
+    def backlinks(self, name: str, *, camelcase: bool = False) -> tuple[BackLink, ...]:
+        """Pages across the union that link to ``name`` (UC-18)."""
+        return build_backlinks(self.union, camelcase=camelcase).to(name)
+
+    def recent_changes(self, *, limit: int | None = None) -> tuple[ChangeEntry, ...]:
+        """The merged newest-first change feed: coordination journal + shard signals (UC-17)."""
+        return recent_changes(self.union, self.log, self.space_id, limit=limit)
+
+    def all_pages(self) -> tuple[AllPagesEntry, ...]:
+        """The union's distinct pages, collapsed via the maintained equivalence index."""
+        return all_pages(self.union, equivalence_groups=self.index.equivalence_groups())
+
+    def site_map(self) -> SiteMapNode:
+        """The union namespace tree built from page placements."""
+        return site_map(self.union)

src/shard_wiki/union/__init__.py

@@ -0,0 +1,8 @@
+"""union/ — the derived-tier union (resolution, equivalence, projection read path).
+
+Disposable/recomputable (I-2); imports down only and is imported by nothing.
+"""
+
+from shard_wiki.union.resolver import Resolution, ResolutionKind, UnionGraph
+
+__all__ = ["UnionGraph", "Resolution", "ResolutionKind"]

src/shard_wiki/union/resolver.py

@@ -0,0 +1,170 @@
+"""Union resolution — the derived-tier read path (CoreArchitectureBlueprint §8.4, ADR-01).
+
+A minimal :class:`UnionGraph` over ≥1 attached shard plus the decision-log fold. ``resolve``
+keys on **identity** (FederationRequirements ADR-01): alias redirect → exact union lookup →
+equivalence chorus → red-link. Ambiguity returns a **chorus set** (union without erasure, I-4):
+divergent peers are recorded in each page's provenance envelope rather than silently dropped.
+
+This is derived/disposable: it reads shards + the log fold; it stores nothing canonical. Per the
+dependency rule it may import down (model/adapters/coordination/policy/provenance) and is
+imported by nothing.
+"""
+
+from __future__ import annotations
+
+import dataclasses
+from collections.abc import Iterator
+from dataclasses import dataclass
+from enum import Enum
+
+from shard_wiki.adapters import ShardAdapter
+from shard_wiki.coordination import DecisionLog, Overlay
+from shard_wiki.model import Identity, Page
+from shard_wiki.policy import DEFAULT_POLICY, CanonicalSource, Policy
+from shard_wiki.provenance import OverlayState, ProvenanceEnvelope, Staleness
+
+__all__ = ["ResolutionKind", "Resolution", "UnionGraph"]
+
+
+class ResolutionKind(Enum):
+    SINGLE = "single"
+    CHORUS = "chorus"
+    RED_LINK = "red-link"
+
+
+@dataclass(frozen=True, slots=True)
+class Resolution:
+    name: str
+    kind: ResolutionKind
+    pages: tuple[Page, ...] = ()
+
+    @property
+    def is_red_link(self) -> bool:
+        return self.kind is ResolutionKind.RED_LINK
+
+    def single(self) -> Page:
+        """The one page (SINGLE), or the canonical pick of a CHORUS (first), else KeyError."""
+        if not self.pages:
+            raise KeyError(self.name)
+        return self.pages[0]
+
+
+class UnionGraph:
+    """Composes attached shards + the coordination-log fold into a resolvable union."""
+
+    def __init__(
+        self,
+        space: str,
+        log: DecisionLog | None = None,
+        policy: Policy = DEFAULT_POLICY,
+    ) -> None:
+        self.space = space
+        self.log = log or DecisionLog()
+        self.policy = policy
+        self._shards: list[ShardAdapter] = []
+
+    def attach(self, adapter: ShardAdapter) -> None:
+        self._shards.append(adapter)
+
+    def shard(self, shard_id: str) -> ShardAdapter | None:
+        return next((s for s in self._shards if s.shard_id == shard_id), None)
+
+    @property
+    def shards(self) -> tuple[ShardAdapter, ...]:
+        return tuple(self._shards)
+
+    def iter_pages(self) -> Iterator[Page]:
+        """Every page across attached shards, raw (per-shard, not chorus-collapsed). The
+        enumeration substrate for derived views — BackLinks, AllPages, SiteMap (§8.4)."""
+        for shard in self._shards:
+            for key in shard.keys():
+                try:
+                    yield shard.read(key)
+                except KeyError:
+                    continue
+
+    def _read_all(self, key: str) -> list[Page]:
+        pages: list[Page] = []
+        for shard in self._shards:
+            try:
+                pages.append(shard.read(key))
+            except KeyError:
+                continue
+        return pages
+
+    def resolve(self, name: str) -> Resolution:
+        state = self.log.fold(self.space)
+        overlays = {
+            Overlay.from_payload(p).target: Overlay.from_payload(p)
+            for p in state.open_overlays.values()
+        }
+
+        # 1. alias redirect (coordination-canonical, via the log fold)
+        target = state.resolve_alias(name)
+        if target is not None and ":" in target:
+            shard_id, _, key = target.partition(":")
+            shard = self.shard(shard_id)
+            if shard is not None:
+                try:
+                    page = self._with_overlay(shard.read(key), overlays)
+                    return Resolution(name, ResolutionKind.SINGLE, (page,))
+                except KeyError:
+                    pass  # alias dangles → fall through to normal resolution
+
+        # 2/3. union lookup by key across shards, then layer open overlays
+        pages = [self._with_overlay(p, overlays) for p in self._read_all(name)]
+        pages.extend(self._draft_only_pages(name, pages, overlays))
+
+        if not pages:
+            return Resolution(name, ResolutionKind.RED_LINK)
+        if len(pages) == 1:
+            return Resolution(name, ResolutionKind.SINGLE, (pages[0],))
+
+        # ambiguity → chorus, with divergence recorded (never erased, I-4)
+        ordered = self._order_for_policy(pages)
+        marked = tuple(_with_divergence(p, ordered) for p in ordered)
+        return Resolution(name, ResolutionKind.CHORUS, marked)
+
+    def _with_overlay(self, page: Page, overlays: dict[Identity, Overlay]) -> Page:
+        """Mark a canonical page that has an open overlay (overlay_state DRAFT; project the
+        overlaid body where policy shows drafts) — never hides the overlay (I-4)."""
+        overlay = overlays.get(page.identity)
+        if overlay is None:
+            return page
+        env = dataclasses.replace(page.envelope, overlay_state=OverlayState.DRAFT)
+        body = overlay.body if self.policy.show_drafts else page.body
+        return dataclasses.replace(page, body=body, envelope=env)
+
+    def _draft_only_pages(
+        self, name: str, existing: list[Page], overlays: dict[Identity, Overlay]
+    ) -> list[Page]:
+        """Drafts that create a not-yet-existing page on an attached shard become resolvable."""
+        have = {p.identity for p in existing}
+        out: list[Page] = []
+        for identity, overlay in overlays.items():
+            if identity.key != name or identity in have or self.shard(identity.shard) is None:
+                continue
+            env = ProvenanceEnvelope(
+                source_shard=identity.shard,
+                staleness=Staleness.FRESH,
+                overlay_state=OverlayState.DRAFT,
+            )
+            body = overlay.body if self.policy.show_drafts else ""
+            out.append(Page(identity=identity, body=body, envelope=env))
+        return out
+
+    def _order_for_policy(self, pages: list[Page]) -> list[Page]:
+        if (
+            self.policy.canonical_source is CanonicalSource.DESIGNATED_CANONICAL
+            and self.policy.designated_shard is not None
+        ):
+            pages = sorted(
+                pages, key=lambda p: p.identity.shard != self.policy.designated_shard
+            )
+        return pages
+
+
+def _with_divergence(page: Page, group: list[Page]) -> Page:
+    peers = tuple(str(p.identity) for p in group if p.identity != page.identity)
+    new_env = dataclasses.replace(page.envelope, divergence=peers)
+    return dataclasses.replace(page, envelope=new_env)

src/shard_wiki/views/__init__.py

@@ -0,0 +1,33 @@
+"""views/ — derived, recomputable, provenance-carrying read views over the union (§8.4).
+
+All views here are *derived tier*: pure functions of the attached shards plus the coordination-log
+fold, storing nothing canonical (SHARD-WP-0011 makes them incrementally maintainable). Presentation
+stays out of core (L6) — these produce models, never rendered output. Per the dependency rule this
+package imports down (union/model/coordination/provenance) and is imported only by the orchestrator.
+"""
+
+from shard_wiki.views.allpages import AllPagesEntry, SiteMapNode, all_pages, site_map
+from shard_wiki.views.backlinks import BackLink, BackLinksIndex, build_backlinks
+from shard_wiki.views.links import (
+    ResolvedLink,
+    WikiLink,
+    extract_links,
+    resolve_links,
+)
+from shard_wiki.views.recentchanges import ChangeEntry, recent_changes
+
+__all__ = [
+    "WikiLink",
+    "ResolvedLink",
+    "extract_links",
+    "resolve_links",
+    "BackLink",
+    "BackLinksIndex",
+    "build_backlinks",
+    "ChangeEntry",
+    "recent_changes",
+    "AllPagesEntry",
+    "SiteMapNode",
+    "all_pages",
+    "site_map",
+]

src/shard_wiki/views/allpages.py

@@ -0,0 +1,131 @@
+"""AllPages + SiteMap — enumeration views over the union (SHARD-WP-0010 T4).
+
+**AllPages** lists the union's distinct pages, collapsing identities that name the same page: a
+*chorus* (same key across shards) and *equivalence-bound* identities (decision-log bindings) fold
+into one entry, with divergence noted when the members' bodies differ (union without erasure — the
+collapse is acknowledged, never silent). **SiteMap** is the namespace tree built from page
+placements (paths), spanning shards.
+
+Both are derived/recomputable and presentation-free (the tree is a model, not rendered HTML).
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+from shard_wiki.model import Identity, Page
+from shard_wiki.union import UnionGraph
+
+__all__ = ["AllPagesEntry", "SiteMapNode", "all_pages", "site_map"]
+
+
+@dataclass(frozen=True, slots=True)
+class AllPagesEntry:
+    """One union page: its representative ``name``, the ``members`` collapsed into it, and whether
+    those members' bodies ``diverge`` (a chorus with differing content)."""
+
+    name: str
+    members: tuple[Identity, ...]
+    diverges: bool
+
+
+@dataclass(frozen=True, slots=True)
+class SiteMapNode:
+    """A namespace node: its path ``name``, child namespaces, and pages directly under it."""
+
+    name: str
+    children: tuple[SiteMapNode, ...]
+    pages: tuple[Identity, ...]
+
+
+class _UnionFind:
+    def __init__(self) -> None:
+        self._parent: dict[str, str] = {}
+
+    def add(self, x: str) -> None:
+        self._parent.setdefault(x, x)
+
+    def find(self, x: str) -> str:
+        self.add(x)
+        root = x
+        while self._parent[root] != root:
+            root = self._parent[root]
+        while self._parent[x] != root:
+            self._parent[x], x = root, self._parent[x]
+        return root
+
+    def union(self, a: str, b: str) -> None:
+        self.add(a)
+        self.add(b)
+        ra, rb = self.find(a), self.find(b)
+        if ra != rb:
+            self._parent[max(ra, rb)] = min(ra, rb)
+
+
+def all_pages(
+    union: UnionGraph,
+    equivalence_groups: tuple[frozenset[str], ...] | None = None,
+) -> tuple[AllPagesEntry, ...]:
+    """Enumerate the union's distinct pages, collapsing chorus + equivalence-bound members.
+
+    ``equivalence_groups`` (string identities, decision-log form) overrides the source of
+    equivalence — the orchestrator passes the maintained index's groups (SHARD-WP-0011 T4); the
+    default falls back to the decision-log fold, so direct callers are unaffected.
+    """
+    pages: dict[str, Page] = {}
+    by_key: dict[str, list[str]] = {}
+    for page in union.iter_pages():
+        ident = str(page.identity)
+        pages[ident] = page
+        by_key.setdefault(page.identity.key, []).append(ident)
+
+    uf = _UnionFind()
+    for ident in pages:
+        uf.add(ident)
+    for idents in by_key.values():  # same key across shards → chorus
+        for other in idents[1:]:
+            uf.union(idents[0], other)
+    if equivalence_groups is None:
+        equivalence_groups = union.log.fold(union.space).equivalence_groups
+    for group in equivalence_groups:  # curator bindings (+ maintained content edges)
+        present = [m for m in group if m in pages]
+        for other in present[1:]:
+            uf.union(present[0], other)
+
+    groups: dict[str, list[str]] = {}
+    for ident in pages:
+        groups.setdefault(uf.find(ident), []).append(ident)
+
+    entries: list[AllPagesEntry] = []
+    for members in groups.values():
+        member_pages = [pages[m] for m in members]
+        identities = tuple(p.identity for p in member_pages)
+        name = min(p.identity.key for p in member_pages)
+        diverges = len({p.body for p in member_pages}) > 1
+        entries.append(AllPagesEntry(name=name, members=identities, diverges=diverges))
+    return tuple(sorted(entries, key=lambda e: e.name))
+
+
+def _segments(page: Page) -> list[str]:
+    path = page.placements[0].path if page.placements else page.identity.key
+    if path.endswith(".md"):
+        path = path[:-3]
+    return [seg for seg in path.split("/") if seg]
+
+
+def site_map(union: UnionGraph) -> SiteMapNode:
+    """The union namespace tree from page placements (directories nest; pages sit at their dir)."""
+    root: dict = {"children": {}, "pages": []}
+    for page in union.iter_pages():
+        segments = _segments(page)
+        node = root
+        for seg in segments[:-1]:  # directory segments build the nesting
+            node = node["children"].setdefault(seg, {"children": {}, "pages": []})
+        node["pages"].append(page.identity)
+    return _freeze("", root)
+
+
+def _freeze(name: str, node: dict) -> SiteMapNode:
+    children = tuple(_freeze(k, v) for k, v in sorted(node["children"].items()))
+    pages = tuple(sorted(node["pages"], key=str))
+    return SiteMapNode(name=name, children=children, pages=pages)

src/shard_wiki/views/backlinks.py

@@ -0,0 +1,65 @@
+"""BackLinks — the strongest core derived view (SHARD-WP-0010 T2; UC-18).
+
+For any page name, the set of pages that link to it. Built by extracting wikilinks (T1) from every
+page across the attached shards and resolving each through the union: only **resolved** links
+create a backlink (a red-link points at nothing, so it contributes none). Entries carry their
+**source provenance** (the linking page's identity / shard). Keying by the resolved *name* means a
+chorus target aggregates the backlinks of all its members into one bucket (union without erasure).
+
+Derived/recomputable — stores nothing canonical; SHARD-WP-0011 maintains it incrementally.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Mapping
+from dataclasses import dataclass
+
+from shard_wiki.model import Identity
+from shard_wiki.union import UnionGraph
+from shard_wiki.views.links import resolve_links
+
+__all__ = ["BackLink", "BackLinksIndex", "build_backlinks"]
+
+
+@dataclass(frozen=True, slots=True)
+class BackLink:
+    """One inbound link: ``source`` (the linking page) references ``target_name``."""
+
+    source: Identity
+    target_name: str
+
+    @property
+    def source_shard(self) -> str:
+        return self.source.shard
+
+
+class BackLinksIndex:
+    """An immutable name → inbound-links index over the union link graph."""
+
+    def __init__(self, edges: Mapping[str, tuple[BackLink, ...]]) -> None:
+        self._edges = dict(edges)
+
+    def to(self, name: str) -> tuple[BackLink, ...]:
+        """The backlinks pointing at ``name`` (empty if none)."""
+        return self._edges.get(name, ())
+
+    def sources(self, name: str) -> frozenset[Identity]:
+        """Just the identities linking to ``name`` — convenient for set assertions."""
+        return frozenset(bl.source for bl in self.to(name))
+
+    def names(self) -> frozenset[str]:
+        return frozenset(self._edges)
+
+
+def build_backlinks(union: UnionGraph, *, camelcase: bool = False) -> BackLinksIndex:
+    """Scan every union page's links and index the resolved ones by target name."""
+    edges: dict[str, set[BackLink]] = {}
+    for page in union.iter_pages():
+        for resolved in resolve_links(union, page.body, camelcase=camelcase):
+            if resolved.is_red_link:
+                continue  # red-links don't create backlinks
+            backlink = BackLink(source=page.identity, target_name=resolved.link.target)
+            edges.setdefault(resolved.link.target, set()).add(backlink)
+    return BackLinksIndex(
+        {name: tuple(sorted(links, key=lambda bl: str(bl.source))) for name, links in edges.items()}
+    )

src/shard_wiki/views/links.py

@@ -0,0 +1,91 @@
+"""Wikilink + red-link model (SHARD-WP-0010 T1; FederationRequirements ADR-06).
+
+A CommonMark *wikilink extension*: ``[[Target]]`` and ``[[Target|label]]`` are extracted from a
+page body and each target is resolved through the union (ADR-01). A target that resolves is a
+**link**; one that does not is a **red-link** — a createable hole (UC-23), never a dropped
+reference (union without erasure). CamelCase auto-linking (``WikiWord``) is **off by default** and
+opt-in per space, since bare CamelCase is noisy and policy-laden.
+
+The link *model and resolution* are core; turning a :class:`ResolvedLink` into an ``<a>`` (or a
+red anchor) is L6 presentation and lives outside this package. Link spans are byte/char offsets in
+the body so a later layer can address them precisely.
+"""
+
+from __future__ import annotations
+
+import re
+from dataclasses import dataclass
+
+from shard_wiki.union import Resolution, UnionGraph
+
+__all__ = ["WikiLink", "ResolvedLink", "extract_links", "resolve_links"]
+
+_WIKILINK_RE = re.compile(r"\[\[\s*([^\]|]+?)\s*(?:\|\s*([^\]]+?)\s*)?\]\]")
+# A WikiWord: ≥2 capitalized alphanumeric segments run together (e.g. FrontPage, WikiWord).
+_CAMELCASE_RE = re.compile(r"\b([A-Z][a-z0-9]+(?:[A-Z][a-z0-9]+)+)\b")
+_FENCED_RE = re.compile(r"```.*?```", re.DOTALL)
+_INLINE_CODE_RE = re.compile(r"`[^`\n]*`")
+
+
+@dataclass(frozen=True, slots=True)
+class WikiLink:
+    """One extracted reference. ``target`` is the resolve key; ``label`` is the display text (or
+    None to use the target); ``span`` is the ``[start, end)`` offset of the whole token in the body;
+    ``auto`` marks a CamelCase auto-link (vs an explicit ``[[...]]``)."""
+
+    target: str
+    label: str | None
+    span: tuple[int, int]
+    auto: bool = False
+
+    @property
+    def text(self) -> str:
+        return self.label or self.target
+
+
+@dataclass(frozen=True, slots=True)
+class ResolvedLink:
+    """A :class:`WikiLink` paired with its union :class:`Resolution` (the link's truth status)."""
+
+    link: WikiLink
+    resolution: Resolution
+
+    @property
+    def is_red_link(self) -> bool:
+        return self.resolution.is_red_link
+
+
+def _mask(body: str, pattern: re.Pattern[str]) -> str:
+    """Blank out ``pattern`` matches with equal-length spaces so later scans skip them while every
+    surviving match keeps its true offset."""
+    return pattern.sub(lambda m: " " * len(m.group(0)), body)
+
+
+def extract_links(body: str, *, camelcase: bool = False) -> tuple[WikiLink, ...]:
+    """Extract wikilinks from ``body`` in document order, skipping fenced/inline code.
+
+    With ``camelcase=True`` (per-space opt-in), bare ``WikiWord`` tokens outside code and outside
+    existing ``[[...]]`` also become links.
+    """
+    scan = _mask(_mask(body, _FENCED_RE), _INLINE_CODE_RE)
+    links: list[WikiLink] = []
+    for m in _WIKILINK_RE.finditer(scan):
+        links.append(WikiLink(target=m.group(1).strip(), label=m.group(2), span=m.span()))
+
+    if camelcase:
+        # Mask explicit-link spans too, so a CamelCase target inside [[...]] isn't double-counted.
+        cc_scan = _mask(scan, _WIKILINK_RE)
+        for m in _CAMELCASE_RE.finditer(cc_scan):
+            links.append(WikiLink(target=m.group(1), label=None, span=m.span(), auto=True))
+
+    return tuple(sorted(links, key=lambda link: link.span[0]))
+
+
+def resolve_links(
+    union: UnionGraph, body: str, *, camelcase: bool = False
+) -> tuple[ResolvedLink, ...]:
+    """Extract and resolve every link in ``body`` against ``union`` (link vs red-link, ADR-01)."""
+    return tuple(
+        ResolvedLink(link, union.resolve(link.target))
+        for link in extract_links(body, camelcase=camelcase)
+    )

src/shard_wiki/views/recentchanges.py

@@ -0,0 +1,108 @@
+"""RecentChanges — a merged change feed over the union (SHARD-WP-0010 T3; UC-17).
+
+Two streams, one ordered feed (newest-first):
+
+* the **coordination journal** — overlay/alias/fork/merge/binding decisions from the decision log,
+  each carrying its actor and the decision payload; and
+* **shard change signals** — a page's current revision (folder mtime / ``source_rev``), i.e. the
+  backend's own "this changed" evidence.
+
+Every entry carries provenance: which shard the edit came from, or that it was a coordination
+decision (and by whom). Derived/recomputable — `notify`-driven streaming is a later binding.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Mapping
+from dataclasses import dataclass, field
+from datetime import datetime
+
+from shard_wiki.coordination import DecisionLog, EventType
+from shard_wiki.union import UnionGraph
+
+__all__ = ["ChangeEntry", "recent_changes"]
+
+_COORDINATION = "coordination"
+
+# How each journal event names the thing it touched + a human kind label.
+_EVENT_KIND = {
+    EventType.ALIAS_SET: "alias",
+    EventType.OVERLAY_CREATED: "overlay",
+    EventType.MERGE_DECIDED: "merge",
+    EventType.PAGE_FORKED: "fork",
+    EventType.BINDING_MADE: "binding",
+}
+
+
+@dataclass(frozen=True, slots=True)
+class ChangeEntry:
+    """One change in the feed. ``source`` is the shard id (a shard edit) or ``"coordination"``."""
+
+    when: datetime
+    kind: str
+    ref: str
+    source: str
+    actor: str | None = None
+    detail: Mapping[str, object] = field(default_factory=dict)
+
+
+def _event_ref(event_type: EventType, payload: Mapping[str, object]) -> str:
+    if event_type is EventType.ALIAS_SET:
+        return str(payload.get("alias", ""))
+    if event_type is EventType.OVERLAY_CREATED:
+        return f"{payload.get('target_shard')}:{payload.get('target_key')}"
+    if event_type is EventType.PAGE_FORKED:
+        return f"{payload.get('source')}→{payload.get('fork')}"
+    if event_type is EventType.BINDING_MADE:
+        return ", ".join(str(m) for m in payload.get("members", ()))
+    return str(payload.get("overlay_id", ""))  # MERGE_DECIDED
+
+
+def recent_changes(
+    union: UnionGraph,
+    log: DecisionLog,
+    space: str,
+    *,
+    limit: int | None = None,
+) -> tuple[ChangeEntry, ...]:
+    """Merge the coordination journal and shard change signals into one newest-first feed."""
+    entries: list[ChangeEntry] = []
+
+    for event in log.events(space):
+        entries.append(
+            ChangeEntry(
+                when=event.timestamp,
+                kind=_EVENT_KIND.get(event.type, event.type.value),
+                ref=_event_ref(event.type, event.payload),
+                source=_COORDINATION,
+                actor=event.actor,
+                detail=dict(event.payload),
+            )
+        )
+
+    for page in union.iter_pages():
+        rev = page.envelope.source_rev
+        when = _parse_rev(rev)
+        if when is None:
+            continue  # shard offers no change signal for this page — skip gracefully
+        entries.append(
+            ChangeEntry(
+                when=when,
+                kind="edit",
+                ref=str(page.identity),
+                source=page.identity.shard,
+                detail={"source_rev": rev},
+            )
+        )
+
+    entries.sort(key=lambda e: e.when, reverse=True)
+    return tuple(entries if limit is None else entries[:limit])
+
+
+def _parse_rev(rev: str | None) -> datetime | None:
+    if rev is None:
+        return None
+    try:
+        return datetime.fromisoformat(rev)
+    except ValueError:
+        return None  # non-temporal revision token (e.g. a content hash) — no feed timestamp

tests/test_append_authority.py

@@ -0,0 +1,120 @@
+"""Tests for the per-space append authority / lease (SHARD-WP-0009 T2).
+
+A single append authority per space serializes appends into a total order; non-holders forward
+intents to the holder; the lease is time-bounded and re-grantable (HA hand-off); a stale ex-holder
+cannot fork the log.
+"""
+
+from datetime import datetime, timedelta, timezone
+
+import pytest
+
+from shard_wiki.coordination import (
+    AppendAuthority,
+    EventType,
+    GitEventStore,
+    InMemoryEventStore,
+    LeaseHeld,
+    LeaseRegistry,
+)
+
+
+class FakeClock:
+    def __init__(self):
+        self.now = datetime(2026, 1, 1, tzinfo=timezone.utc)
+
+    def __call__(self):
+        return self.now
+
+    def advance(self, seconds):
+        self.now += timedelta(seconds=seconds)
+
+
+def test_only_one_node_holds_a_space_at_a_time():
+    reg = LeaseRegistry()
+    a = AppendAuthority("A", InMemoryEventStore(), reg)
+    b = AppendAuthority("B", InMemoryEventStore(), reg)
+    a.acquire("s")
+    with pytest.raises(LeaseHeld):
+        b.acquire("s")  # B is refused while A's lease is valid
+
+
+def test_concurrent_appends_serialize_into_one_total_order():
+    reg = LeaseRegistry()
+    store = InMemoryEventStore()
+    a = AppendAuthority("A", store, reg)
+    b = AppendAuthority("B", store, reg)
+    a.acquire("s")
+    # B is a non-holder: its append forwards to A, the holder. Interleave A and B writers.
+    a.append("s", EventType.ALIAS_SET, {"alias": "1", "target": "x:1"})
+    b.append("s", EventType.ALIAS_SET, {"alias": "2", "target": "x:2"})  # forwarded
+    a.append("s", EventType.ALIAS_SET, {"alias": "3", "target": "x:3"})
+    seqs = [e.seq for e in store.events("s")]
+    aliases = [e.payload["alias"] for e in store.events("s")]
+    assert seqs == [0, 1, 2]  # contiguous total order despite two writers
+    assert aliases == ["1", "2", "3"]
+
+
+def test_non_holder_forwards_rather_than_writing_directly():
+    reg = LeaseRegistry()
+    store = InMemoryEventStore()
+    a = AppendAuthority("A", store, reg)
+    b = AppendAuthority("B", store, reg)
+    a.acquire("s")
+    assert not b.holds("s")
+    b.append("s", EventType.ALIAS_SET, {"alias": "fwd", "target": "x:1"})
+    # The write landed on the shared store under A's authority, in one stream.
+    assert [e.payload["alias"] for e in store.events("s")] == ["fwd"]
+
+
+def test_lease_handoff_resumes_from_head():
+    clock = FakeClock()
+    reg = LeaseRegistry(clock=clock)
+    store = InMemoryEventStore()
+    a = AppendAuthority("A", store, reg, ttl_seconds=10)
+    b = AppendAuthority("B", store, reg, ttl_seconds=10)
+    a.acquire("s")
+    a.append("s", EventType.ALIAS_SET, {"alias": "0", "target": "x:0"})
+    a.append("s", EventType.ALIAS_SET, {"alias": "1", "target": "x:1"})
+    clock.advance(20)  # A's lease expires (A "dies")
+    b.acquire("s")  # re-grantable: B takes over
+    b.append("s", EventType.ALIAS_SET, {"alias": "2", "target": "x:2"})
+    assert [e.seq for e in store.events("s")] == [0, 1, 2]  # contiguous across hand-off
+
+
+def test_stale_ex_holder_cannot_fork_the_log():
+    clock = FakeClock()
+    reg = LeaseRegistry(clock=clock)
+    store = InMemoryEventStore()
+    a = AppendAuthority("A", store, reg, ttl_seconds=10)
+    b = AppendAuthority("B", store, reg, ttl_seconds=10)
+    a.acquire("s")
+    a.append("s", EventType.ALIAS_SET, {"alias": "0", "target": "x:0"})
+    clock.advance(20)
+    b.acquire("s")  # B is now the holder; A's lease is stale
+    b.append("s", EventType.ALIAS_SET, {"alias": "1", "target": "x:1"})
+    # A still thinks it can write, but it's no longer the holder: its intent forwards to B.
+    assert not a.holds("s")
+    a.append("s", EventType.ALIAS_SET, {"alias": "2", "target": "x:2"})
+    aliases = [e.payload["alias"] for e in store.events("s")]
+    assert aliases == ["0", "1", "2"]  # one stream, no fork
+
+
+def test_authority_over_git_store_keeps_total_order(tmp_path):
+    reg = LeaseRegistry()
+    store = GitEventStore(tmp_path / "coord")
+    a = AppendAuthority("A", store, reg)
+    b = AppendAuthority("B", store, reg)
+    a.acquire("s")
+    a.append("s", EventType.BINDING_MADE, {"members": ["a", "b"]})
+    b.append("s", EventType.PAGE_FORKED, {"source": "a", "fork": "c"})  # forwarded
+    assert [e.seq for e in store.events("s")] == [0, 1]
+
+
+def test_unleased_space_self_acquires_on_append():
+    reg = LeaseRegistry()
+    store = InMemoryEventStore()
+    a = AppendAuthority("A", store, reg)
+    a.append("s", EventType.ALIAS_SET, {"alias": "x", "target": "y:1"})  # no explicit acquire
+    assert a.holds("s")
+    assert len(store.events("s")) == 1

tests/test_apply.py

@@ -0,0 +1,66 @@
+"""Tests for apply-under-drift (SHARD-WP-0008 T4)."""
+
+from shard_wiki.adapters import FolderAdapter
+from shard_wiki.coordination import ApplyStatus, DecisionLog, OverlayEngine
+from shard_wiki.model import Identity
+
+
+def _writable(tmp_path, files):
+    for rel, text in files.items():
+        (tmp_path / rel).write_text(text, encoding="utf-8")
+    return FolderAdapter("w", tmp_path, writable=True)
+
+
+def test_fast_forward_apply_writes_through(tmp_path):
+    shard = _writable(tmp_path, {"Home.md": "old"})
+    eng = OverlayEngine("space", DecisionLog())
+    base = shard.current_rev("Home")
+    ov = eng.draft(Identity("w", "Home"), "new", base_rev=base)
+
+    result = eng.apply(ov.overlay_id, shard)
+    assert result.status is ApplyStatus.APPLIED
+    assert shard.read("Home").body == "new"  # written through
+    assert eng.get(ov.overlay_id) is None  # overlay closed in the fold
+
+
+def test_drift_refuses_without_clobber(tmp_path):
+    shard = _writable(tmp_path, {"Home.md": "old"})
+    eng = OverlayEngine("space", DecisionLog())
+    ov = eng.draft(Identity("w", "Home"), "mine", base_rev="STALE-REV")
+
+    result = eng.apply(ov.overlay_id, shard)
+    assert result.status is ApplyStatus.REFUSED_DRIFT
+    assert shard.read("Home").body == "old"  # not clobbered (I-5)
+    assert eng.get(ov.overlay_id) is not None  # overlay still open
+
+
+def test_read_only_target_keeps_draft(tmp_path):
+    (tmp_path / "Home.md").write_text("canon", encoding="utf-8")
+    ro = FolderAdapter("ro", tmp_path)  # not writable
+    eng = OverlayEngine("space", DecisionLog())
+    ov = eng.draft(Identity("ro", "Home"), "my edit", base_rev=ro.current_rev("Home"))
+
+    result = eng.apply(ov.overlay_id, ro)
+    assert result.status is ApplyStatus.KEPT_DRAFT
+    assert ro.read("Home").body == "canon"  # source untouched
+    assert eng.get(ov.overlay_id) is not None  # local truth retained
+
+
+def test_new_page_fast_forwards(tmp_path):
+    shard = _writable(tmp_path, {})
+    eng = OverlayEngine("space", DecisionLog())
+    ov = eng.draft(Identity("w", "Fresh"), "brand new", base_rev=None)  # didn't exist
+    result = eng.apply(ov.overlay_id, shard)
+    assert result.status is ApplyStatus.APPLIED
+    assert shard.read("Fresh").body == "brand new"
+
+
+def test_wrong_adapter_is_rejected(tmp_path):
+    shard = _writable(tmp_path, {"Home.md": "x"})
+    eng = OverlayEngine("space", DecisionLog())
+    ov = eng.draft(Identity("other", "Home"), "y", base_rev=None)
+    try:
+        eng.apply(ov.overlay_id, shard)
+        raise AssertionError("expected ValueError")
+    except ValueError:
+        pass

tests/test_conformance.py

@@ -0,0 +1,67 @@
+"""Tests for the adapter conformance suite (SHARD-WP-0007 T4)."""
+
+from collections.abc import Iterable
+
+import pytest
+
+from shard_wiki.adapters import (
+    ConformanceError,
+    FolderAdapter,
+    ShardAdapter,
+    assert_conformant,
+    run_conformance,
+)
+from shard_wiki.model import CapabilityProfile, Identity, Page
+from shard_wiki.provenance import ProvenanceEnvelope
+
+
+def test_folder_adapter_is_conformant(tmp_path):
+    (tmp_path / "Home.md").write_text("# Home", encoding="utf-8")
+    report = assert_conformant(FolderAdapter("shardA", tmp_path))
+    assert report.ok
+    assert report.diff() == "conformant"
+
+
+class _LyingReadAdapter(ShardAdapter):
+    """Claims READ but read() is broken — must fail conformance."""
+
+    def __init__(self, profile: CapabilityProfile) -> None:
+        self._profile = profile
+
+    @property
+    def shard_id(self) -> str:
+        return "liar"
+
+    def profile(self) -> CapabilityProfile:
+        return self._profile
+
+    def keys(self) -> Iterable[str]:
+        return ["Home"]
+
+    def read(self, key: str) -> Page:
+        # Returns a page attributed to the WRONG shard — a lie about its own content.
+        return Page(Identity("someone-else", key), "x", ProvenanceEnvelope(source_shard="x"))
+
+
+def test_lying_read_adapter_fails_with_precise_diff(tmp_path):
+    good = FolderAdapter("shardA", tmp_path).profile()  # a valid read-only profile
+    liar = _LyingReadAdapter(good)
+    report = run_conformance(liar)
+    assert not report.ok
+    assert "read-round-trips" in report.diff()
+    with pytest.raises(ConformanceError, match="read-round-trips"):
+        assert_conformant(liar)
+
+
+class _DishonestWriteAdapter(FolderAdapter):
+    """Declares no WRITE (inherits read-only folder profile) but write() silently succeeds."""
+
+    def write(self, key: str, body: str) -> Page:  # noqa: ARG002
+        return self.read(next(iter(self.keys())))
+
+
+def test_dishonest_absence_fails(tmp_path):
+    (tmp_path / "Home.md").write_text("x", encoding="utf-8")
+    report = run_conformance(_DishonestWriteAdapter("shardA", tmp_path))
+    assert not report.ok
+    assert "honest-absence:write" in report.diff()

tests/test_coordination_migration.py

@@ -0,0 +1,74 @@
+"""Migration + wiring of the git coordination backend (SHARD-WP-0009 T4)."""
+
+from shard_wiki.coordination import (
+    DecisionLog,
+    EventType,
+    GitEventStore,
+    InMemoryEventStore,
+    export_jsonl,
+    import_jsonl,
+    migrate_space,
+)
+from shard_wiki.space import InformationSpace
+
+
+def test_information_space_git_backed_uses_git_log(tmp_path):
+    space = InformationSpace.git_backed("space-1", tmp_path / "coord")
+    assert isinstance(space.log._store, GitEventStore)
+    space.alias("Home", "shardA:Index")
+    # Read-your-writes through the orchestrator's git-backed log.
+    assert space.log.fold("space-1").resolve_alias("Home") == "shardA:Index"
+
+
+def test_default_information_space_stays_in_memory():
+    space = InformationSpace("space-1")
+    assert isinstance(space.log._store, InMemoryEventStore)
+
+
+def test_migrate_space_preserves_order_and_provenance(tmp_path):
+    source = InMemoryEventStore()
+    e0 = source.append("s", EventType.ALIAS_SET, {"alias": "Home", "target": "x:1"}, actor="ana")
+    source.append("s", EventType.BINDING_MADE, {"members": ["a", "b"]}, actor="ben")
+
+    dest = GitEventStore(tmp_path / "coord")
+    n = migrate_space(source, "s", dest)
+    assert n == 2
+
+    migrated = dest.events("s")
+    assert [e.seq for e in migrated] == [0, 1]
+    # Provenance preserved verbatim — actor and timestamp survive the move (no restamping).
+    assert migrated[0].actor == "ana"
+    assert migrated[1].actor == "ben"
+    assert migrated[0].timestamp == e0.timestamp
+
+
+def test_migration_yields_identical_fold(tmp_path):
+    source = DecisionLog(InMemoryEventStore())
+    for typ, payload in [
+        (EventType.ALIAS_SET, {"alias": "Home", "target": "x:1"}),
+        (EventType.BINDING_MADE, {"members": ["a", "b"]}),
+        (EventType.BINDING_MADE, {"members": ["b", "c"]}),
+        (EventType.ALIAS_SET, {"alias": "Home", "target": "x:2"}),
+    ]:
+        source.append("s", typ, payload)
+
+    dest = GitEventStore(tmp_path / "coord")
+    migrate_space(source._store, "s", dest)
+    after = DecisionLog(dest)
+    assert after.fold("s").aliases == source.fold("s").aliases
+    assert after.fold("s").equivalence_groups == source.fold("s").equivalence_groups
+
+
+def test_jsonl_round_trip_into_git(tmp_path):
+    source = InMemoryEventStore()
+    source.append("s", EventType.ALIAS_SET, {"alias": "Home", "target": "x:1"})
+    source.append("s", EventType.PAGE_FORKED, {"source": "p", "fork": "q"})
+
+    path = tmp_path / "log.jsonl"
+    assert export_jsonl(source.events("s"), path) == 2
+
+    dest = GitEventStore(tmp_path / "coord")
+    assert import_jsonl(path, dest) == 2
+    state = DecisionLog(dest).fold("s")
+    assert state.resolve_alias("Home") == "x:1"
+    assert state.equivalent_to("p") == frozenset({"p", "q"})

tests/test_cross_process_fold.py

@@ -0,0 +1,83 @@
+"""Cross-process read-your-writes over the git log + fold parity (SHARD-WP-0009 T3).
+
+The git backend's value over the in-memory double is that the totally ordered log is durable and
+shared: a write by one process/handle is immediately visible to another opening the same ref, and
+the derived fold is identical to the in-memory fold of the same event sequence (derived = f(log)).
+"""
+
+import os
+import subprocess
+import sys
+import textwrap
+from pathlib import Path
+
+from shard_wiki.coordination import (
+    DecisionLog,
+    EventType,
+    GitEventStore,
+    InMemoryEventStore,
+)
+
+_SRC = str(Path(__file__).resolve().parents[1] / "src")
+
+
+def test_new_handle_sees_prior_writes(tmp_path):
+    repo = tmp_path / "coord"
+    writer = DecisionLog(GitEventStore(repo))
+    writer.append("s", EventType.ALIAS_SET, {"alias": "Home", "target": "shardA:Index"})
+    writer.append("s", EventType.BINDING_MADE, {"members": ["a", "b"]})
+    # A second, independent handle on the same repo — read-your-writes across handles.
+    reader = DecisionLog(GitEventStore(repo))
+    assert [e.seq for e in reader.events("s")] == [0, 1]
+    assert reader.fold("s").resolve_alias("Home") == "shardA:Index"
+
+
+def test_append_in_separate_process_is_visible(tmp_path):
+    repo = tmp_path / "coord"
+    # Seed from this process so the repo exists.
+    DecisionLog(GitEventStore(repo)).append(
+        "s", EventType.ALIAS_SET, {"alias": "A", "target": "x:1"}
+    )
+    child = textwrap.dedent(
+        f"""
+        from shard_wiki.coordination import DecisionLog, EventType, GitEventStore
+        log = DecisionLog(GitEventStore({str(repo)!r}))
+        log.append("s", EventType.ALIAS_SET, {{"alias": "B", "target": "x:2"}})
+        """
+    )
+    result = subprocess.run(
+        [sys.executable, "-c", child],
+        capture_output=True,
+        text=True,
+        env={"PYTHONPATH": _SRC, "PATH": os.environ.get("PATH", "")},
+    )
+    assert result.returncode == 0, result.stderr
+    # This process, with a fresh handle, sees the child's append in order.
+    reader = DecisionLog(GitEventStore(repo))
+    assert [e.payload["alias"] for e in reader.events("s")] == ["A", "B"]
+    assert [e.seq for e in reader.events("s")] == [0, 1]
+
+
+def test_cross_process_fold_equals_in_memory_fold(tmp_path):
+    sequence = [
+        (EventType.ALIAS_SET, {"alias": "Home", "target": "shardA:Index"}),
+        (EventType.BINDING_MADE, {"members": ["a", "b"]}),
+        (EventType.BINDING_MADE, {"members": ["b", "c"]}),
+        (EventType.PAGE_FORKED, {"source": "p", "fork": "q"}),
+        (EventType.ALIAS_SET, {"alias": "Home", "target": "shardB:Main"}),
+    ]
+    mem = DecisionLog(InMemoryEventStore())
+    for typ, payload in sequence:
+        mem.append("s", typ, payload)
+
+    repo = tmp_path / "coord"
+    DecisionLog(GitEventStore(repo))  # init repo
+    for typ, payload in sequence:
+        # Each append from a fresh handle to simulate distinct writers over time.
+        DecisionLog(GitEventStore(repo)).append("s", typ, payload)
+
+    git_state = DecisionLog(GitEventStore(repo)).fold("s")
+    mem_state = mem.fold("s")
+    assert git_state.aliases == mem_state.aliases
+    assert git_state.equivalence_groups == mem_state.equivalence_groups
+    assert git_state.equivalent_to("a") == frozenset({"a", "b", "c"})

tests/test_decision_log.py

@@ -0,0 +1,51 @@
+"""Tests for the event-sourced DecisionLog (SHARD-WP-0007 T5)."""
+
+from shard_wiki.coordination import DecisionLog, EventType
+
+
+def test_append_is_totally_ordered_per_space():
+    log = DecisionLog()
+    log.append("spaceA", EventType.ALIAS_SET, {"alias": "Home", "target": "shardA:Index"})
+    log.append("spaceA", EventType.ALIAS_SET, {"alias": "Start", "target": "shardA:Index"})
+    log.append("spaceB", EventType.ALIAS_SET, {"alias": "X", "target": "shardB:Y"})
+    seqs = [e.seq for e in log.events("spaceA")]
+    assert seqs == [0, 1]  # per-space monotonic
+    assert [e.seq for e in log.events("spaceB")] == [0]  # independent ordering
+
+
+def test_read_your_writes():
+    log = DecisionLog()
+    ev = log.append("s", EventType.ALIAS_SET, {"alias": "a", "target": "shardA:b"})
+    assert log.events("s")[-1] is ev
+
+
+def test_fold_reproduces_current_state():
+    log = DecisionLog()
+    log.append("s", EventType.ALIAS_SET, {"alias": "Home", "target": "shardA:Index"})
+    log.append("s", EventType.ALIAS_SET, {"alias": "Home", "target": "shardB:Main"})  # LWW
+    state = log.fold("s")
+    assert state.resolve_alias("Home") == "shardB:Main"
+    assert state.resolve_alias("missing") is None
+
+
+def test_fold_is_pure_function_of_log():
+    log = DecisionLog()
+    log.append("s", EventType.BINDING_MADE, {"members": ["shardA:Home", "shardB:Home"]})
+    first = log.fold("s")
+    second = log.fold("s")
+    assert first.equivalence_groups == second.equivalence_groups  # derived = f(log)
+
+
+def test_equivalence_groups_merge_transitively():
+    log = DecisionLog()
+    log.append("s", EventType.BINDING_MADE, {"members": ["a", "b"]})
+    log.append("s", EventType.BINDING_MADE, {"members": ["b", "c"]})
+    state = log.fold("s")
+    assert state.equivalent_to("a") == frozenset({"a", "b", "c"})
+    assert state.equivalent_to("lonely") == frozenset({"lonely"})
+
+
+def test_page_fork_creates_equivalence():
+    log = DecisionLog()
+    log.append("s", EventType.PAGE_FORKED, {"source": "shardA:Doc", "fork": "shardB:Doc"})
+    assert log.fold("s").equivalent_to("shardA:Doc") == frozenset({"shardA:Doc", "shardB:Doc"})

tests/test_engine_activation.py

@@ -0,0 +1,61 @@
+"""Tests for per-shard extension activation (SHARD-WP-0014 T3, ADR-0001)."""
+
+from shard_wiki.engine import (
+    ActivationContext,
+    ActivationResolver,
+    StaticProvider,
+    feature_control_provider,
+)
+
+CANDIDATES = ["ext.overlay", "ext.views", "ext.struct", "ext.compute"]
+
+
+def test_static_provider_default_off():
+    r = ActivationResolver(StaticProvider())  # nothing enabled
+    assert r.active_extensions(CANDIDATES, ActivationContext("s")) == set()
+
+
+def test_static_provider_global_flags():
+    r = ActivationResolver(StaticProvider(flags={"ext.overlay": True, "ext.views": True}))
+    assert r.active_extensions(CANDIDATES, ActivationContext("s")) == {"ext.overlay", "ext.views"}
+
+
+def test_per_shard_scoping_overrides_global():
+    provider = StaticProvider(
+        flags={"ext.views": True},
+        per_shard={"engB": {"ext.struct": True, "ext.views": False}},
+    )
+    r = ActivationResolver(provider)
+    assert r.active_extensions(CANDIDATES, ActivationContext("engA")) == {"ext.views"}
+    assert r.active_extensions(CANDIDATES, ActivationContext("engB")) == {"ext.struct"}
+
+
+def test_context_carries_tenant():
+    captured = {}
+
+    class Spy(StaticProvider):
+        def is_active(self, feature_key, context):
+            captured.update(context)
+            return super().is_active(feature_key, context)
+
+    ActivationResolver(Spy(flags={"ext.views": True})).active_extensions(
+        ["ext.views"], ActivationContext("s1", tenant_id="acme")
+    )
+    assert captured["shard_id"] == "s1" and captured["tenant_id"] == "acme"
+
+
+def test_activation_profile_returns_config_for_active():
+    provider = StaticProvider(
+        flags={"ext.struct": True},
+        configs={"ext.struct": {"max_fields": 50}},
+    )
+    profile = ActivationResolver(provider).activation_profile(CANDIDATES, ActivationContext("s"))
+    assert profile == {"ext.struct": {"max_fields": 50}}
+
+
+def test_feature_control_provider_degrades_gracefully():
+    # feature_control_sdk is not a dependency of shard-wiki: when absent the factory returns
+    # None (standalone path stays dependency-free, ADR-0001); when present it yields a usable
+    # ActivationProvider. Either way it must not raise.
+    provider = feature_control_provider()
+    assert provider is None or hasattr(provider, "is_active")

tests/test_engine_adapter.py

@@ -0,0 +1,80 @@
+"""Tests for EngineShardAdapter (SHARD-WP-0014 T5): engine as a canonical-mode shard."""
+
+from shard_wiki import InformationSpace
+from shard_wiki.adapters import assert_conformant
+from shard_wiki.engine import (
+    Extension,
+    ExtensionRuntime,
+    Hook,
+    ProfileContribution,
+    StaticProvider,
+    build_engine_shard,
+)
+from shard_wiki.engine.activation import ActivationContext
+from shard_wiki.model import Verb
+
+
+class StructProfileExt(Extension):
+    """Profile-only extension (no body transform → write stays content-preserving)."""
+
+    id = "ext.struct"
+
+    def hooks(self):
+        return {
+            Hook.ON_PROFILE: lambda p, c: ProfileContribution(
+                verbs_add=frozenset({Verb.STRUCTURED_PAYLOAD})
+            )
+        }
+
+
+def _runtime():
+    rt = ExtensionRuntime()
+    rt.register(StructProfileExt())
+    return rt
+
+
+def test_kernel_only_engine_shard_is_conformant():
+    shard = build_engine_shard("eng", ExtensionRuntime(), activate=set())
+    shard.write("Home", "hi")
+    report = assert_conformant(shard)            # read + positive write probe
+    assert report.ok
+    assert shard.profile().supports(Verb.WRITE)
+    assert not shard.profile().supports(Verb.STRUCTURED_PAYLOAD)
+
+
+def test_profile_reflects_activated_extensions():
+    off = build_engine_shard("a", _runtime(), activate=set())
+    on = build_engine_shard("b", _runtime(), activate={"ext.struct"})
+    assert not off.profile().supports(Verb.STRUCTURED_PAYLOAD)
+    assert on.profile().supports(Verb.STRUCTURED_PAYLOAD)   # E-5
+    assert_conformant(on)
+
+
+def test_activation_via_provider():
+    provider = StaticProvider(flags={"ext.struct": True})
+    shard = build_engine_shard("c", _runtime(), provider=provider, context=ActivationContext("c"))
+    assert shard.profile().supports(Verb.STRUCTURED_PAYLOAD)
+
+
+def test_attach_resolve_edit_through_engine_shard(tmp_path):
+    space = InformationSpace("team")
+    space.attach(build_engine_shard("wikiE", ExtensionRuntime(), activate=set()))
+    # seed a page directly via the shard, then read + edit through the orchestrator
+    space.union.shard("wikiE").write("Home", "v1")
+    assert space.read("Home").body == "v1"
+    result = space.edit("Home", "v2")            # overlay -> apply-under-drift -> write-through
+    assert result.status.value == "applied"
+    assert space.read("Home").body == "v2"
+
+
+def test_on_write_transform_runs():
+    class Upper(Extension):
+        id = "ext.upper"
+        def hooks(self):
+            return {Hook.ON_WRITE: lambda body, ctx: body.upper()}
+
+    rt = ExtensionRuntime()
+    rt.register(Upper())
+    shard = build_engine_shard("u", rt, activate={"ext.upper"})
+    shard.write("P", "quiet")
+    assert shard.read("P").body == "QUIET"       # extension transformed the write

tests/test_engine_extension.py

@@ -0,0 +1,109 @@
+"""Tests for the typed-extension runtime (SHARD-WP-0014 T2)."""
+
+import pytest
+
+from shard_wiki.engine import Extension, ExtensionError, ExtensionRuntime, Hook
+
+
+class Upper(Extension):
+    id = "ext.upper"
+    declares_types = ("upper",)
+
+    def hooks(self):
+        return {Hook.ON_WRITE: lambda body, ctx: body.upper()}
+
+
+class Bang(Extension):
+    id = "ext.bang"
+    depends_on = ("ext.upper",)
+
+    def hooks(self):
+        return {Hook.ON_WRITE: lambda body, ctx: body + "!"}
+
+
+class Profiler(Extension):
+    id = "ext.profiler"
+
+    def hooks(self):
+        return {Hook.ON_PROFILE: lambda payload, ctx: {"structure": "typed"}}
+
+
+def _runtime(*exts):
+    rt = ExtensionRuntime()
+    for e in exts:
+        rt.register(e)
+    return rt
+
+
+def test_register_rejects_bad_id_and_noncallable_hook():
+    rt = ExtensionRuntime()
+    class BadId(Extension):
+        id = "upper"  # missing 'ext.' prefix
+    with pytest.raises(ExtensionError, match="ext."):
+        rt.register(BadId())
+
+    class Liar(Extension):
+        id = "ext.liar"
+        def hooks(self):
+            return {Hook.ON_WRITE: "not-callable"}  # type: ignore[dict-item]
+    with pytest.raises(ExtensionError, match="not callable"):
+        rt.register(Liar())
+
+
+def test_transform_hook_chains_in_dependency_order():
+    rt = _runtime(Upper(), Bang())
+    active = rt.activate({"ext.bang"})  # pulls ext.upper via depends_on
+    assert set(active.ids) == {"ext.upper", "ext.bang"}
+    # upper (dependency) runs before bang (dependent): "hi" -> "HI" -> "HI!"
+    assert active.handlers(Hook.ON_WRITE) == ("ext.upper", "ext.bang")
+    assert active.dispatch_transform(Hook.ON_WRITE, "hi") == "HI!"
+
+
+def test_dependency_closure_is_automatic():
+    rt = _runtime(Upper(), Bang())
+    assert set(rt.activate({"ext.bang"}).ids) == {"ext.upper", "ext.bang"}
+
+
+def test_unknown_extension_rejected():
+    with pytest.raises(ExtensionError, match="unknown"):
+        ExtensionRuntime().activate({"ext.ghost"})
+
+
+def test_conflict_rejected():
+    class A(Extension):
+        id = "ext.a"
+        conflicts_with = ("ext.b",)
+    class B(Extension):
+        id = "ext.b"
+    with pytest.raises(ExtensionError, match="conflicts"):
+        _runtime(A(), B()).activate({"ext.a", "ext.b"})
+
+
+def test_type_collision_rejected():
+    class S1(Extension):
+        id = "ext.s1"
+        declares_types = ("record",)
+    class S2(Extension):
+        id = "ext.s2"
+        declares_types = ("record",)
+    with pytest.raises(ExtensionError, match="type collision"):
+        _runtime(S1(), S2()).activate({"ext.s1", "ext.s2"})
+
+
+def test_collect_hook_gathers_contributions():
+    active = _runtime(Profiler()).activate({"ext.profiler"})
+    assert active.dispatch_collect(Hook.ON_PROFILE) == [{"structure": "typed"}]
+
+
+def test_wrong_dispatch_kind_errors():
+    active = _runtime(Profiler()).activate({"ext.profiler"})
+    with pytest.raises(ExtensionError, match="not a transform hook"):
+        active.dispatch_transform(Hook.ON_PROFILE, "x")
+
+
+def test_unmet_dependency_rejected():
+    # Bang depends on ext.upper, but only Bang is registered.
+    rt = ExtensionRuntime()
+    rt.register(Bang())
+    with pytest.raises(ExtensionError, match="unmet dependency|unknown"):
+        rt.activate({"ext.bang"})

tests/test_engine_kernel.py

@@ -0,0 +1,59 @@
+"""Tests for the engine kernel (SHARD-WP-0014 T1)."""
+
+import pytest
+
+from shard_wiki.engine import EngineKernel, extract_wikilinks
+from shard_wiki.model import Identity
+
+
+def test_write_creates_then_edits_as_history():
+    k = EngineKernel("eng")
+    p1 = k.write("Home", "first")
+    assert p1.identity == Identity("eng", "Home")
+    assert p1.envelope.source_rev == "1"
+    p2 = k.write("Home", "second")
+    assert p2.envelope.source_rev == "2"
+    assert k.read("Home").body == "second"          # latest
+    assert [v.body for v in k.history("Home")] == ["first", "second"]  # recoverable history
+
+
+def test_read_missing_raises():
+    k = EngineKernel("eng")
+    with pytest.raises(KeyError):
+        k.read("Nope")
+
+
+def test_delete_is_recoverable():
+    k = EngineKernel("eng")
+    k.write("Doc", "v1")
+    k.delete("Doc")
+    assert not k.exists("Doc")
+    with pytest.raises(KeyError):
+        k.read("Doc")
+    assert [v.body for v in k.history("Doc")] == ["v1"]   # history retained
+    k.write("Doc", "v2")                                   # restore by writing
+    assert k.exists("Doc") and k.read("Doc").body == "v2"
+
+
+def test_keys_and_current_rev():
+    k = EngineKernel("eng")
+    k.write("A", "a")
+    k.write("B", "b")
+    k.write("A", "a2")
+    assert set(k.keys()) == {"A", "B"}
+    assert k.current_rev("A") == "2"
+    assert k.current_rev("Missing") is None
+
+
+def test_links_and_red_link_resolution():
+    k = EngineKernel("eng")
+    k.write("Home", "see [[Target]] and [[Other|labelled]] and [[Target]] again")
+    k.write("Target", "exists")
+    assert k.links("Home") == ["Target", "Other"]        # ordered, de-duped, label dropped
+    assert k.resolve_link("Target") == Identity("eng", "Target")
+    assert k.resolve_link("Other") is None               # red-link (not yet created)
+
+
+def test_extract_wikilinks_helper():
+    assert extract_wikilinks("none here") == []
+    assert extract_wikilinks("[[A]] [[B|x]] [[A]]") == ["A", "B"]

tests/test_engine_profile.py

@@ -0,0 +1,98 @@
+"""Tests for capability-profile-derived-from-extensions (SHARD-WP-0014 T4, E-5)."""
+
+import pytest
+
+from shard_wiki.engine import (
+    Extension,
+    ExtensionRuntime,
+    Hook,
+    ProfileContribution,
+    derive_profile,
+    engine_base_profile,
+)
+from shard_wiki.model import (
+    Addressing,
+    ContentOpacity,
+    NativeQuery,
+    ProfileError,
+    Verb,
+)
+
+
+class StructExt(Extension):
+    id = "ext.struct"
+
+    def hooks(self):
+        return {
+            Hook.ON_PROFILE: lambda payload, ctx: ProfileContribution(
+                verbs_add=frozenset({Verb.STRUCTURED_PAYLOAD})
+            )
+        }
+
+
+class AddrExt(Extension):
+    id = "ext.addr"
+
+    def hooks(self):
+        return {
+            Hook.ON_PROFILE: lambda payload, ctx: ProfileContribution(
+                addressing=Addressing.SPAN, verbs_add=frozenset({Verb.TRANSCLUDE_SOURCE})
+            )
+        }
+
+
+class EncryptExt(Extension):
+    id = "ext.encrypt"
+
+    def hooks(self):
+        return {Hook.ON_PROFILE: lambda p, c: ProfileContribution(content_opacity=ContentOpacity.ENCRYPTED)}
+
+
+class QueryExt(Extension):
+    id = "ext.query"
+
+    def hooks(self):
+        return {Hook.ON_PROFILE: lambda p, c: ProfileContribution(native_query=NativeQuery.DB_QUERY)}
+
+
+def _active(*exts, ids=None):
+    rt = ExtensionRuntime()
+    for e in exts:
+        rt.register(e)
+    return rt.activate(ids if ids is not None else {e.id for e in exts})
+
+
+def test_base_profile_is_valid_kernel_minimum():
+    p = engine_base_profile()
+    assert p.supports(Verb.READ) and p.supports(Verb.WRITE)
+    assert not p.supports(Verb.STRUCTURED_PAYLOAD)
+    assert p.addressing is Addressing.PATH
+
+
+def test_no_extensions_yields_base():
+    rt = ExtensionRuntime()
+    active = rt.activate(set())
+    assert derive_profile(active) == engine_base_profile()
+
+
+def test_activating_extension_raises_the_profile():
+    active = _active(StructExt(), AddrExt())
+    p = derive_profile(active)
+    assert p.supports(Verb.STRUCTURED_PAYLOAD)      # from ext.struct
+    assert p.supports(Verb.TRANSCLUDE_SOURCE)       # from ext.addr
+    assert p.addressing is Addressing.SPAN          # raised by ext.addr
+    assert p.supports(Verb.READ)                    # base preserved
+
+
+def test_profile_changes_with_active_set():
+    only_struct = derive_profile(_active(StructExt(), AddrExt(), ids={"ext.struct"}))
+    both = derive_profile(_active(StructExt(), AddrExt()))
+    assert not only_struct.supports(Verb.TRANSCLUDE_SOURCE)
+    assert both.supports(Verb.TRANSCLUDE_SOURCE)    # E-5: profile reflects what's active
+
+
+def test_composition_cannot_yield_an_impossible_profile():
+    # encrypted opacity + native query violates §6.5 implication rules -> derive must reject.
+    active = _active(EncryptExt(), QueryExt())
+    with pytest.raises(ProfileError):
+        derive_profile(active)

tests/test_error_paths.py

@@ -0,0 +1,76 @@
+"""Error-path / contract tests across modules (keeps the suite honest about failure behaviour)."""
+
+from collections.abc import Iterable
+
+import pytest
+
+from shard_wiki import InformationSpace
+from shard_wiki.adapters import FolderAdapter, ShardAdapter, run_conformance
+from shard_wiki.engine import EngineKernel
+from shard_wiki.model import CapabilityProfile, Identity, Page, Placement
+from shard_wiki.provenance import ProvenanceEnvelope
+from shard_wiki.union import ResolutionKind, UnionGraph
+
+
+def _folder(tmp_path, name, files, writable=False):
+    root = tmp_path / name
+    root.mkdir(parents=True, exist_ok=True)
+    for rel, text in files.items():
+        (root / rel).write_text(text, encoding="utf-8")
+    return FolderAdapter(name, root, writable=writable)
+
+
+def test_resolution_single_on_red_link_raises():
+    u = UnionGraph("s")
+    res = u.resolve("ghost")
+    assert res.kind is ResolutionKind.RED_LINK
+    with pytest.raises(KeyError):
+        res.single()
+
+
+def test_apply_unknown_overlay_raises(tmp_path):
+    space = InformationSpace("t")
+    space.attach(_folder(tmp_path, "w", {"Home.md": "x"}, writable=True))
+    with pytest.raises(KeyError):
+        space.apply_overlay("does-not-exist")
+
+
+def test_apply_overlay_for_unattached_shard_raises(tmp_path):
+    space = InformationSpace("t")
+    space.attach(_folder(tmp_path, "w", {"Home.md": "x"}, writable=True))
+    # draft an overlay whose target shard is not attached -> apply can't find an adapter
+    ov = space.overlays.draft(Identity("ghost", "X"), "body", base_rev=None)
+    with pytest.raises(KeyError):
+        space.apply_overlay(ov.overlay_id)
+
+
+def test_kernel_delete_missing_raises():
+    with pytest.raises(KeyError):
+        EngineKernel("eng").delete("nope")
+
+
+def test_placement_str():
+    assert str(Placement("shardA", "sub/Page")) == "shardA/sub/Page"
+
+
+class _BrokenProfileAdapter(ShardAdapter):
+    """profile() raises — the conformance battery must report failure, not crash."""
+
+    @property
+    def shard_id(self) -> str:
+        return "broken"
+
+    def profile(self) -> CapabilityProfile:
+        raise RuntimeError("profile blew up")
+
+    def keys(self) -> Iterable[str]:
+        return []
+
+    def read(self, key: str) -> Page:
+        return Page(Identity("broken", key), "x", ProvenanceEnvelope(source_shard="broken"))
+
+
+def test_conformance_survives_a_broken_profile():
+    report = run_conformance(_BrokenProfileAdapter())
+    assert not report.ok
+    assert any(c.name == "profile-validates" and not c.ok for c in report.checks)

tests/test_ext_struct.py

@@ -0,0 +1,64 @@
+"""Tests for the ext.struct built-in extension (SHARD-WP-0014 T6)."""
+
+import pytest
+
+from shard_wiki import InformationSpace
+from shard_wiki.adapters import assert_conformant
+from shard_wiki.engine import ExtensionRuntime, build_engine_shard
+from shard_wiki.engine.extensions import StructExt, parse_frontmatter
+from shard_wiki.model import PageShape, Verb
+
+_STRUCT_PAGE = "---\ntitle: Spec\nstatus: draft\n---\nbody text"
+
+
+def test_parse_frontmatter():
+    fields, has = parse_frontmatter(_STRUCT_PAGE)
+    assert has and fields == {"title": "Spec", "status": "draft"}
+    assert parse_frontmatter("just prose") == ({}, False)
+    assert parse_frontmatter("---\nunterminated") == ({}, False)
+
+
+def _runtime(allowed=None):
+    rt = ExtensionRuntime()
+    rt.register(StructExt(allowed_fields=allowed))
+    return rt
+
+
+def test_feature_absent_when_extension_off():
+    shard = build_engine_shard("off", ExtensionRuntime(), activate=set())
+    shard.write("Spec", _STRUCT_PAGE)
+    assert shard.read("Spec").shape is PageShape.PROSE          # kernel: opaque prose
+    assert not shard.profile().supports(Verb.STRUCTURED_PAYLOAD)  # honest absence
+
+
+def test_feature_present_when_extension_on():
+    shard = build_engine_shard("on", _runtime(), activate={"ext.struct"})
+    shard.write("Spec", _STRUCT_PAGE)
+    assert shard.read("Spec").shape is PageShape.TYPED_RECORD   # tagged by ext.struct
+    assert shard.read("Spec").body.endswith("body text")        # content preserved (in-text)
+    assert shard.profile().supports(Verb.STRUCTURED_PAYLOAD)    # profile reflects activation (E-5)
+    assert_conformant(shard)                                     # still conformant
+
+
+def test_plain_page_is_not_tagged_even_when_on():
+    shard = build_engine_shard("on", _runtime(), activate={"ext.struct"})
+    shard.write("Plain", "no frontmatter here")
+    assert shard.read("Plain").shape is PageShape.PROSE
+
+
+def test_allowed_fields_validation_rejects_disallowed():
+    shard = build_engine_shard("v", _runtime(allowed={"title"}), activate={"ext.struct"})
+    with pytest.raises(ValueError, match="disallowed fields"):
+        shard.write("Bad", "---\ntitle: ok\nsecret: no\n---\nx")
+    shard.write("Good", "---\ntitle: ok\n---\nx")               # allowed field passes
+    assert shard.read("Good").shape is PageShape.TYPED_RECORD
+
+
+def test_through_information_space_edit():
+    space = InformationSpace("team")
+    space.attach(build_engine_shard("wikiE", _runtime(), activate={"ext.struct"}))
+    space.union.shard("wikiE").write("Doc", "---\ntitle: T\n---\nv1")
+    res = space.edit("Doc", "---\ntitle: T2\n---\nv2")           # overlay→apply→write-through
+    assert res.status.value == "applied"
+    page = space.read("Doc")
+    assert page.shape is PageShape.TYPED_RECORD and "v2" in page.body

tests/test_folder_adapter.py

@@ -0,0 +1,44 @@
+"""Tests for the FolderAdapter (SHARD-WP-0007 T3)."""
+
+import pytest
+
+from shard_wiki.adapters import FolderAdapter
+from shard_wiki.model import Identity, NotSupported, Verb
+
+
+def _make_shard(tmp_path, files: dict[str, str]) -> FolderAdapter:
+    for rel, text in files.items():
+        p = tmp_path / rel
+        p.parent.mkdir(parents=True, exist_ok=True)
+        p.write_text(text, encoding="utf-8")
+    return FolderAdapter("shardA", tmp_path)
+
+
+def test_keys_and_read(tmp_path):
+    shard = _make_shard(tmp_path, {"Home.md": "# Home", "sub/Topic.md": "topic body"})
+    assert set(shard.keys()) == {"Home", "sub/Topic"}
+    page = shard.read("sub/Topic")
+    assert page.identity == Identity("shardA", "sub/Topic")
+    assert page.body == "topic body"
+    assert page.envelope.source_shard == "shardA"
+    assert page.envelope.source_rev is not None  # mtime stamp
+    assert page.placements[0].path == "sub/Topic.md"
+
+
+def test_read_missing_raises_keyerror(tmp_path):
+    shard = _make_shard(tmp_path, {"Home.md": "x"})
+    with pytest.raises(KeyError):
+        shard.read("Nope")
+
+
+def test_profile_is_valid_and_read_only(tmp_path):
+    shard = _make_shard(tmp_path, {"Home.md": "x"})
+    prof = shard.profile()  # .validate() already called inside
+    assert prof.supports(Verb.READ)
+    assert not prof.supports(Verb.WRITE)
+
+
+def test_unsupported_write_is_honest(tmp_path):
+    shard = _make_shard(tmp_path, {"Home.md": "x"})
+    with pytest.raises(NotSupported):
+        shard.write("Home", "new")

tests/test_git_adapter.py

@@ -0,0 +1,131 @@
+"""Tests for the GitShardAdapter read path + profile (SHARD-WP-0012 T1)."""
+
+import subprocess
+
+import pytest
+
+from shard_wiki.adapters import GitShardAdapter, run_conformance
+from shard_wiki.model import (
+    AttachmentMode,
+    History,
+    NotSupported,
+    ProfileError,
+    Substrate,
+    Verb,
+)
+
+
+def _git(repo, *args):
+    subprocess.run(
+        ["git", "-C", str(repo), *args],
+        check=True,
+        capture_output=True,
+        env={"GIT_AUTHOR_NAME": "t", "GIT_AUTHOR_EMAIL": "t@t",
+             "GIT_COMMITTER_NAME": "t", "GIT_COMMITTER_EMAIL": "t@t",
+             "PATH": __import__("os").environ.get("PATH", "")},
+    )
+
+
+def _repo(tmp_path, files, name="repo"):
+    repo = tmp_path / name
+    repo.mkdir()
+    _git(repo, "init", "--quiet")
+    for rel, text in files.items():
+        p = repo / rel
+        p.parent.mkdir(parents=True, exist_ok=True)
+        p.write_text(text, encoding="utf-8")
+        _git(repo, "add", rel)
+    _git(repo, "commit", "-m", "seed")
+    return repo
+
+
+def test_keys_are_tracked_md_paths(tmp_path):
+    repo = _repo(tmp_path, {"Home.md": "h", "docs/Guide.md": "g", "ignore.txt": "x"})
+    adapter = GitShardAdapter("git", repo)
+    assert set(adapter.keys()) == {"Home", "docs/Guide"}  # only tracked *.md
+
+
+def test_read_returns_page_with_commit_sha_rev(tmp_path):
+    repo = _repo(tmp_path, {"Home.md": "welcome"})
+    adapter = GitShardAdapter("git", repo)
+    page = adapter.read("Home")
+    assert page.identity.shard == "git"
+    assert page.body == "welcome"
+    head = subprocess.run(
+        ["git", "-C", str(repo), "rev-parse", "HEAD"], capture_output=True, text=True, check=True
+    ).stdout.strip()
+    assert page.envelope.source_rev == head  # source_rev is the commit sha
+    assert page.envelope.lineage == "git-native"
+
+
+def test_read_missing_key_raises(tmp_path):
+    adapter = GitShardAdapter("git", _repo(tmp_path, {"Home.md": "h"}))
+    with pytest.raises(KeyError):
+        adapter.read("Nope")
+
+
+def test_profile_validates_implication_rules(tmp_path):
+    profile = GitShardAdapter("git", _repo(tmp_path, {"Home.md": "h"})).profile()
+    assert profile.substrate is Substrate.GIT
+    assert profile.attachment_mode is AttachmentMode.GIT_IS_STORE
+    assert profile.history is History.GIT_NATIVE  # git-is-store ⟹ git-native
+    profile.validate()  # raises if the implication rule were violated
+
+
+def test_profile_is_read_only_in_t1(tmp_path):
+    profile = GitShardAdapter("git", _repo(tmp_path, {"Home.md": "h"})).profile()
+    assert profile.supports(Verb.READ)
+    assert not profile.supports(Verb.WRITE)
+
+
+def test_conformance_read_path_passes(tmp_path):
+    adapter = GitShardAdapter("git", _repo(tmp_path, {"Home.md": "h", "Other.md": "o"}))
+    report = run_conformance(adapter)
+    assert report.ok, report.diff()
+
+
+def test_unclaimed_write_raises_not_supported(tmp_path):
+    adapter = GitShardAdapter("git", _repo(tmp_path, {"Home.md": "h"}))
+    with pytest.raises(NotSupported):
+        adapter.write("Home", "new")  # read-only: honest absence
+
+
+def test_empty_repo_has_no_keys(tmp_path):
+    repo = tmp_path / "empty"
+    repo.mkdir()
+    _git(repo, "init", "--quiet")
+    adapter = GitShardAdapter("git", repo)
+    assert list(adapter.keys()) == []
+
+
+def test_bad_profile_combo_is_rejected():
+    # Sanity: the implication rule that backs the git profile actually bites when violated.
+    from shard_wiki.model import (
+        AccessGrant,
+        Addressing,
+        CapabilityProfile,
+        ContentOpacity,
+        MergeModel,
+        NativeQuery,
+        OperationalEnvelope,
+        Translation,
+        WriteGranularity,
+    )
+    from shard_wiki.provenance import Liveness
+
+    with pytest.raises(ProfileError):
+        CapabilityProfile(
+            substrate=Substrate.FILES,  # not git, but claims git-is-store
+            attachment_mode=AttachmentMode.GIT_IS_STORE,
+            write_granularity=WriteGranularity.NONE,
+            content_opacity=ContentOpacity.TRANSPARENT,
+            operational_envelope=OperationalEnvelope.LOCAL_UNBOUNDED,
+            access_grant=AccessGrant.OPEN,
+            liveness=Liveness.STATIC,
+            history=History.NONE,
+            merge_model=MergeModel.NONE,
+            addressing=Addressing.PATH,
+            native_query=NativeQuery.NONE,
+            translation=Translation.NATIVE,
+            supported_verbs=frozenset({Verb.READ}),
+        ).validate()

tests/test_git_adapter_integration.py

@@ -0,0 +1,116 @@
+"""GitShardAdapter history adopt + cross-substrate integration (SHARD-WP-0012 T3)."""
+
+import os
+import subprocess
+
+import pytest
+
+from shard_wiki.adapters import FolderAdapter, GitShardAdapter
+from shard_wiki.coordination import ApplyStatus
+from shard_wiki.space import InformationSpace
+
+_ENV = {
+    "GIT_AUTHOR_NAME": "t", "GIT_AUTHOR_EMAIL": "t@t",
+    "GIT_COMMITTER_NAME": "t", "GIT_COMMITTER_EMAIL": "t@t",
+    "PATH": os.environ.get("PATH", ""),
+}
+
+
+def _git(repo, *args):
+    return subprocess.run(
+        ["git", "-C", str(repo), *args], check=True, capture_output=True, text=True, env=_ENV
+    ).stdout.strip()
+
+
+def _git_repo(tmp_path, files, name="git"):
+    repo = tmp_path / name
+    repo.mkdir()
+    _git(repo, "init", "--quiet")
+    for rel, text in files.items():
+        (repo / rel).parent.mkdir(parents=True, exist_ok=True)
+        (repo / rel).write_text(text, encoding="utf-8")
+        _git(repo, "add", rel)
+    _git(repo, "commit", "-m", "seed")
+    return repo
+
+
+def _folder(tmp_path, name, files, writable=False):
+    root = tmp_path / name
+    for rel, text in files.items():
+        p = root / rel
+        p.parent.mkdir(parents=True, exist_ok=True)
+        p.write_text(text, encoding="utf-8")
+    return FolderAdapter(name, root, writable=writable)
+
+
+# -- history adopt -------------------------------------------------------------
+
+
+def test_history_lists_commits_newest_first(tmp_path):
+    repo = _git_repo(tmp_path, {"Home.md": "v1"})
+    adapter = GitShardAdapter("git", repo, writable=True)
+    adapter.write("Home", "v2")
+    history = adapter.history("Home")
+    assert len(history) == 2
+    assert history[0].message == "write Home.md"  # newest first
+    assert history[-1].message == "seed"
+    assert all(rev.sha for rev in history)
+
+
+def test_history_unknown_key_raises(tmp_path):
+    adapter = GitShardAdapter("git", _git_repo(tmp_path, {"Home.md": "h"}))
+    with pytest.raises(KeyError):
+        adapter.history("Nope")
+
+
+# -- cross-substrate integration ----------------------------------------------
+
+
+def test_resolve_across_git_and_folder(tmp_path):
+    space = InformationSpace("space")
+    space.attach(GitShardAdapter("git", _git_repo(tmp_path, {"Home.md": "git home"})))
+    space.attach(_folder(tmp_path, "notes", {"Daily.md": "folder daily"}))
+    assert space.read("Home").body == "git home"  # resolved from the git shard
+    assert space.read("Daily").body == "folder daily"  # resolved from the folder shard
+
+
+def test_chorus_spans_substrates_with_divergence(tmp_path):
+    space = InformationSpace("space")
+    space.attach(GitShardAdapter("git", _git_repo(tmp_path, {"Shared.md": "from git"})))
+    space.attach(_folder(tmp_path, "notes", {"Shared.md": "from folder"}))
+    res = space.resolve("Shared")
+    assert {p.body for p in res.pages} == {"from git", "from folder"}  # chorus across substrates
+    git_page = next(p for p in res.pages if p.identity.shard == "git")
+    assert git_page.envelope.divergence  # divergence recorded, not erased
+
+
+def test_edit_through_git_shard_commits(tmp_path):
+    repo = _git_repo(tmp_path, {"Home.md": "original"})
+    space = InformationSpace("space")
+    space.attach(GitShardAdapter("git", repo, writable=True))
+    result = space.edit("Home", "edited via overlay")
+    assert result.status is ApplyStatus.APPLIED  # write-through fast-forward on a git shard
+    assert space.read("Home").body == "edited via overlay"
+    assert int(_git(repo, "rev-list", "--count", "HEAD")) == 2  # the edit became a commit
+
+
+def test_apply_under_drift_refuses_on_external_commit(tmp_path):
+    repo = _git_repo(tmp_path, {"Home.md": "original"})
+    space = InformationSpace("space")
+    space.attach(GitShardAdapter("git", repo, writable=True))
+    overlay = space.overlay("Home", "my draft")  # base_rev = current git sha
+    # Another writer commits to the same path → the sha moves underneath the draft.
+    (repo / "Home.md").write_text("someone else", encoding="utf-8")
+    _git(repo, "add", "Home.md")
+    _git(repo, "commit", "-m", "external")
+    result = space.apply_overlay(overlay.overlay_id)
+    assert result.status is ApplyStatus.REFUSED_DRIFT  # never clobber (sha drift detected)
+    # The shard itself is untouched — the external commit stands; the draft remains a draft.
+    assert space.union.shard("git").read("Home").body == "someone else"
+
+
+def test_overlay_on_read_only_git_shard_kept_as_draft(tmp_path):
+    space = InformationSpace("space")
+    space.attach(GitShardAdapter("git", _git_repo(tmp_path, {"Home.md": "ro"}), writable=False))
+    result = space.edit("Home", "wanted change")
+    assert result.status is ApplyStatus.KEPT_DRAFT  # read-only target → overlay retained