shard-wiki/workplans/SHARD-WP-0014-engine-implementation.md

id, type, title, domain, repo, status, owner, topic_slug, created, updated, depends_on, state_hub_workstream_id

id	type	title	domain	repo	status	owner	topic_slug	created	updated	depends_on	state_hub_workstream_id
SHARD-WP-0014	workplan	wiki-engine implementation — kernel + typed-extension runtime + activation	whynot	shard-wiki	done	tegwick	whynot	2026-06-15	2026-06-15	SHARD-WP-0007 SHARD-WP-0013	bfce1644-d93d-44c7-af2c-6b0cb50cedd4

SHARD-WP-0014 — Wiki-engine implementation

Goal

Implement the native headless wiki engine specified in spec/WikiEngineCoreArchitecture.md: a small page-store kernel + a stringent typed-extension runtime, with per-shard activation (ADR-0001: via feature-control/OpenFeature, LocalProvider default), the engine's §A capability profile derived from active extensions (E-5), and exposure as a canonical-mode shard (EngineShardAdapter). Target capability: stand up an engine shard, activate a chosen extension set, and attach it to an InformationSpace — its declared capability profile reflecting exactly what is active — proven end-to-end with one real built-in extension.

Non-goal (this slice): the headless network API protocol; git-IS-store backing (kernel uses the existing simple store now; git backing integrates with SHARD-WP-0009/0012 later); computational extensions; the full feature-control control plane. Build the framework, prove it.

Guiding rules (from WikiEngineCoreArchitecture)

• E-1 engine is one shard, not a federation layer. E-2 small kernel. E-3 everything-else is a typed extension. E-4 per-shard activation. E-5 capability profile derived from active extensions. E-8 reuse (feature-control activation; model/provenance/coordination/adapters). E-9 extensions are typed + conformance-verified.
• Honour the §11 dependency rule: engine/ consumes model/, provenance/, coordination/, adapters/, policy/; it is consumed only via its EngineShardAdapter. No orchestrator-tier (union/, projection/) import. Pure-stdlib core; OpenFeature is an optional engine extra.

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Engine kernel skeleton

id: SHARD-WP-0014-T1
status: done
priority: high
state_hub_task_id: "e81ba881-7e92-4581-99ff-b12ad2bcabb3"

src/shard_wiki/engine/kernel.py: the minimal kernel — a page store + lifecycle over existing primitives (reuse model.Page/Identity/provenance; a simple in-memory/folder-backed store now, git-IS-store later) and a recoverable history hook into the decision log. Kernel covers the c2-minimum (create/read/edit-as-history; [[wikilink]]+red-link resolution can be a thin kernel helper). No extensions yet. Tests: page CRUD-as-history; kernel-only shard works.

Typed-extension runtime

id: SHARD-WP-0014-T2
status: done
priority: high
state_hub_task_id: "8ae8e58a-f081-432b-b2c5-b6435fbf3843"

src/shard_wiki/engine/extension.py: the Extension contract (id, provides, types, hooks, depends_on, conflicts_with, config), a registry, a typed hook dispatcher (typed inputs/outputs, declared deterministic order), a type checker, and composition that builds the dependency closure and rejects impossible profiles (conflicts / unmet deps / incompatible types) — the §6.5 discipline for extensions. Extensions ship a conformance check (mirrors §6.6). Tests: register/compose; deterministic hook order; impossible profile rejected; conformance catches a lying extension.

Per-shard activation (feature-control / OpenFeature)

id: SHARD-WP-0014-T3
status: done
priority: high
state_hub_task_id: "c4fe9df4-e6a8-4b7d-891b-59ceec6aebac"

src/shard_wiki/engine/activation.py (ADR-0001): resolve a shard's activation profile ({extension id → config}) through an OpenFeature-shaped client with a static LocalProvider default (standalone, zero external dep); context = {tenant_id: root, shard_id, …}; OpenFeature/ feature-control is an optional provider plugged in when present (degrade gracefully, mirror the identity ladder). Availability only — never authorization. Tests: LocalProvider activates a subset; absent-provider falls back to defaults; context scoping works.

Capability profile derived from active extensions (E-5)

id: SHARD-WP-0014-T4
status: done
priority: high
state_hub_task_id: "15fc8db7-cd80-4675-b387-81aa9bc7d308"

src/shard_wiki/engine/profile.py: fold the active extensions' on_profile contributions into a §A CapabilityProfile (e.g. ext.struct active ⟹ structure spectrum rises + structured-payload verb), then validate() + conformance. Tests: activating an extension changes the derived profile; the derived profile is valid and conformance-passes.

EngineShardAdapter (engine as a canonical-mode shard)

id: SHARD-WP-0014-T5
status: done
priority: high
state_hub_task_id: "2fbf498c-efe9-400a-8a13-7f1b521b3534"

src/shard_wiki/engine/adapter.py: EngineShardAdapter implements adapters.ShardAdapter, backed by the kernel + active extensions, declaring the derived profile (T4). Attach an engine shard to an InformationSpace and read/resolve/edit through it like any shard. Tests + integration: engine shard passes assert_conformant; attach → resolve → edit works.

First built-in extension (prove the framework end-to-end)

id: SHARD-WP-0014-T6
status: done
priority: medium
state_hub_task_id: "b88d1640-9afa-4957-aec3-a7264b09494c"

Implement one real extension end-to-end — ext.views (BackLinks) or ext.struct (typed records) — binding kernel hooks, declaring types, contributing to the derived profile, activatable per shard. Integration test: with the extension OFF the capability is absent (honest profile); ON it works and the profile reflects it. Update SCOPE + spec/README; pytest + pyflakes green.

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Acceptance criteria

• pytest green, pyflakes clean; engine core pure-stdlib (OpenFeature optional, behind the LocalProvider default).
• The vertical slice works: stand up an engine shard, activate a chosen extension set, attach to an InformationSpace; the engine's declared §A profile matches the active extensions and passes conformance.
• Module boundaries honour §11 (engine consumed only via EngineShardAdapter; no union/projection import); E-1…E-9 respected.
• Activation is availability-only (no authz); standalone path has no external dependency.
• Each task committed; state-hub synced.

Suggested task order

T1 kernel → T2 extension runtime → T3 activation → T4 derived profile → T5 EngineShardAdapter → T6 first extension + integration.