shard-wiki/workplans/SHARD-WP-0006-architecture-hardening-2.md

---
id: SHARD-WP-0006
type: workplan
title: "core architecture hardening II (round-2 review fixes)"
domain: whynot
repo: shard-wiki
status: active
owner: tegwick
topic_slug: whynot
created: "2026-06-15"
updated: "2026-06-15"
depends_on:
  - SHARD-WP-0005
---

# SHARD-WP-0006 — Core architecture hardening II

## Goal

Resolve the round-2 review (`history/260615-core-architecture-blueprint-review-2.md`):
reconcile the document's overview with its hardened body (§A), settle the three foundational
gaps (§B: journal concurrency + coordination-state representation; adapter conformance;
incremental-maintenance correctness + I-2 verification), and track the second-tier items
(§C) as open problems. Deliverable: a revised `spec/CoreArchitectureBlueprint.md` that is
**self-consistent** and answers the keystone question — *single- vs multi-writer journal, and
where mutable coordination state actually lives*.

## Context

- Round-2 review: `history/260615-core-architecture-blueprint-review-2.md` (A-1…A-4, B-1…B-4,
  C-1…C-4; resolution §D).
- Round-1 review + first hardening: `history/260615-core-architecture-blueprint-review.md`,
  `SHARD-WP-0005`.
- Constraint to honour: INTENT I-6 / "Git-addressable coordination layer" — any coordination
  store must remain git-addressable (history/patches/review/backup), not abandon Git.

**Non-goal:** Implement anything. Architecture spec revision only.

---

## §A overview-reconciliation pass

```task
id: SHARD-WP-0006-T1
status: todo
priority: high
```

Make the overview match the hardened body (review A-1…A-4):

- **A-1 (bug):** §4 "Page identity vs placement" — remove "equivalence … key on identity";
  state equivalence keys on content fingerprint across identities (align with §7.2).
- **A-2:** §4 "Projection" → trivial-default + extension-point framing (align §8.4); §4
  "Provenance envelope" → layered effective-vs-own (align §7.3).
- **A-3:** §10 policy surface — add the missing knobs (freshness/staleness mode, history
  squash-compaction, conflict-resolution preset, tenant-partition); keep §11's `policy/`
  pointer accurate.
- **A-4:** §3 diagram + §11 header — "incremental-maintained derived tier (rebuild = fallback)"
  and "orthogonal-core capability profile," not "rebuildable cache / 15 spectra."

---

## Journal & coordination-state model (single vs multi-writer)

```task
id: SHARD-WP-0006-T2
status: todo
priority: high
```

Settle the keystone (review B-1 + B-3 together). Decide and document:

- **Separate the content-history journal from the live coordination state.** Proposed
  resolution: **event-sourced coordination** — an append-only **decision log** (overlays,
  bindings, aliases, merges as events) is the **coordination-canonical** tier and is
  **git-addressable** (preserves I-6); the queryable *current* coordination state (effective
  alias table, equivalence set) is a **derived fold** of the log (disposable, indexable, L4).
  This resolves B-3 (representation = event log; queries = derived index) and refines the §1
  three-state framing (coordination-canonical = the decision *log*, not a mutable file).
- **State the concurrency model (B-1).** How multiple orchestrator instances append safely:
  serialized append per space (with the HA story made explicit) and/or
  conflict-free ordering of independent appends; what "read-your-writes" means across
  instances; where Git is authoritative vs a materialised export.
- Update §1 (refine coordination-canonical = decision log), §4 (Coordination journal /
  Overlay), §8.1/§8.2, §8.6 (consistency now grounded on the log + a stated concurrency model),
  §11 (a `coordination/` event-log store + derived-fold index).

---

## Adapter conformance suite (profiles must be verified, not asserted)

```task
id: SHARD-WP-0006-T3
status: todo
priority: high
```

Fix B-2. Make capability-as-data trustworthy: add to the adapter contract (§6) a
**conformance-suite requirement** — a published battery that, given a binding, verifies its
**declared capability profile matches observed behaviour** (each declared verb/position is
exercised; mismatches fail registration). State that an adapter is only admissible if it
passes; that the suite is versioned with the contract; and that profile claims are
**verified, never self-asserted** (this is what makes I-3 / §6.5 sound). Update §6.4/§6.5 and
add the conformance obligation to the acceptance posture.

---

## Incremental-maintenance correctness & I-2 verification

```task
id: SHARD-WP-0006-T4
status: todo
priority: medium
```

Fix B-4. In §8.7: correct the incremental equivalence algorithm — a changed page must
**re-verify the candidate pairs it leaves** (bucket exits) and **propagate** to pages whose
equivalence depended on it, not only its new candidates; the delta is not additive. Add an
**I-2 verification mechanism**: a background consistency-checker comparing a **digest of the
derived tier** against a sampled/periodic recompute, so `derived = f(canonical)` is *verified*,
not merely asserted; on mismatch, recompute the affected partition. State that I-2 is an
*eventually-verified* property with a named checker, and note the residual in §12.

---

## Track second-tier items; close-out

```task
id: SHARD-WP-0006-T5
status: todo
priority: medium
```

Add review §C as open problems in §12 (each with chosen direction + revisit trigger):

- **O-8** preset bundles ("personal vault" / "team wiki" / "enterprise federation") over the
  §10 policy surface — direction: ship a small set of named personas; trigger: operators
  mis-configuring interacting knobs.
- **O-9** shard sharing across roots vs tenant partition (I-13) — direction: shard exclusive to
  one root by default, explicit shared-read binding otherwise; trigger: a shard legitimately
  needed live in two tenants.
- **O-10** span-level authz under transclusion (aggregation/inference leak) + ⊕ composition
  across transclusion boundaries — direction: a transcluded span inherits the *stricter* of
  source and host authz; provenance ⊕ composes source-page-envelope under the host; trigger: a
  cross-authz transclusion in practice.
- **O-11** union-under-shard-unavailability — direction: partial union + per-shard
  "unavailable" provenance + last-known-projection where policy allows; trigger: SLA needs on
  partial reads.

Refresh §14 decisions and §16 traceability (link this review + SHARD-WP-0006); refresh
invariants if any added. Final `check_repo_consistency` pass.

---

## Acceptance criteria

- Every round-2 finding A-1…A-4, B-1…B-4 is **resolved in the blueprint**; C-1…C-4 are tracked
  as O-8…O-11 with a chosen direction (none silently dropped).
- The blueprint is **self-consistent**: overview (§1–§5, §10) agrees with body (§6–§9).
- The **journal/coordination-state model** answers single-vs-multi-writer and preserves I-6
  (git-addressable coordination).
- The **adapter conformance** obligation makes capability-as-data (I-3) verified, not asserted.
- Each task committed; SCOPE/spec-README updated where status changes; state-hub synced.

## Suggested task order

T1 (reconcile, fast) → T2 (keystone journal/coordination model) → T3 (conformance) →
T4 (incremental correctness) → T5 (track §C + close-out).