Contract — ADR-007 ADR file post-state

This task ships exactly one new file plus an index update. No source code, no migrations, no test changes. The deliverable is an Architecture Decision Record draft (status: proposed) that the human or PM can accept, reject, or amend.

File post-state

Path	Operation	Notes
docs/architecture/decisions/ADR-007-eta-session-lifecycle.md	Create	New ADR; numbering reserved (ADR-001–006 exist; 007 is the next free slot).
docs/architecture/decisions/index.md	Update	Add one row to the Index list pointing at ADR-007. Keep the existing ADR-006 row + See-also section unchanged.
docs/audits/adr-007-eta-session-lifecycle-audit.md	Already created	Step 1 artefact.
docs/contracts/adr-007-eta-session-lifecycle-contract.md	This file	Step 2 artefact.
docs/packets/adr-007-eta-session-lifecycle-packet.md	Created in Step 3	Section outline.
docs/verification/adr-007-eta-session-lifecycle-verification.md	Created in Step 5	Deliverable checklist.

No source files (src/**) modified. No data/** modified. No .agents/**, .claude/**, CLAUDE.md, AGENTS.md, colibri-system.md, or other CANON files touched.

ADR shape — required sections (per dispatch deliverable spec)

The ADR must carry:

1. Standard frontmatter. title, description, tags, type: adr, round (this round), status: proposed, parent: Architecture Decision Records, updated: 2026-05-06, nav_order: 70. Match ADR-005 / ADR-006 frontmatter shape byte-for-byte except for the obvious value changes.
2. Title heading + status block. Bold-labelled block listing Status, Date, Round, Supersedes, Superseded by — same shape as ADR-005 lines 15-19.
3. §Context. Explain the three gaps (C1, #6, #7) concretely with code citations carried over from the audit. State why they are tackled together.
4. §Decision. Pick exactly one option for each of the three gaps. Cross-reference between gaps so the choice reads coherent.
5. §Alternatives Considered. At least three options per gap, with a tradeoff note for each. Format as one subsection per gap.
6. §Consequences. Subsections Positive / Negative / Neutral covering runtime, schema, test, and migration impact.
7. §Implementation. Files, migrations, tests, and behavior changes at a level a future executor can split into 5-step tasks. Name the migration filename, the new column names, the new trigger names.
8. §Verification. Concrete checklist Sigma can run to confirm the ADR’s intent was implemented faithfully when the follow-up task ships.
9. §References. Cross-links to ADR-004, ADR-005, ADR-006, the writeback protocol doc, and the audit for this ADR.

Decision-shape requirements

For each gap the §Decision must:

• State the chosen option in one sentence.
• Cite the migration / file / function the choice changes.
• Explicitly call out the deferred parts (what Phase 1+ adds on top).

The recommended cohesive choice from the dispatch packet:

Gap	Recommended option	Notes
C1 (wiring)	Optional session_id on thought_record input + INSERT	Minimum-viable, opt-in. Not breaking — old callers omit it.
#6 (post-finalize guard)	SQLite trigger enforce_post_finalize_guard on thought_records insert/update	Schema-level enforcement. Migration 007_post_finalize_guard.sql.
#7 (ζ↔η coupling)	Per-record back-pointer column thought_records.anchored_in_root set inside merkle_finalize transaction	Bidirectional lookup without a new MCP tool. Preserves ADR-004 14-tool lock.

The contract requires the ADR to either adopt this triple or argue (in §Alternatives Considered) why a different cohesive triple is better. A divergent recommendation must address the same three gaps with options that do not conflict with each other.

Style requirements

• Prose-grade. Each §section opens with at least one paragraph of running prose before any list or table.
• Match ADR-005 voice: declarative, single-letter-concept references (η, ζ, β), explicit phase boundaries.
• Greek letters in prose: η, ζ, β. Code paths in backticks. Cross-ADR refs use [ADR-NNN](ADR-NNN-slug.md) link format (relative within the decisions folder).
• Code citations use the form path/to/file.ts:LINE matching the audit and CLAUDE.md §7 conventions.
• Word count target: 1800–2700 words (ADR-005 is ~1900, ADR-006 has more — the three-gap surface justifies the upper end).

Out of scope (must NOT appear in the ADR file)

• Implementation code. The ADR proposes; follow-up tasks implement.
• Migration SQL bodies (the ADR names the migration and lists the columns/triggers, but does not paste the SQL).
• Test code. The ADR can describe the test class names but must not include Jest source.
• Renumbering of existing ADRs. ADR-001..006 are stable.
• Edits to colibri-system.md, CLAUDE.md, AGENTS.md, or any concept doc.
• Any file outside docs/architecture/decisions/ and the four 5-step chain folders.

Acceptance criteria for the ADR’s §Decision

Criterion	Pass condition
Status	Proposed (NOT Accepted) — the ADR is a draft for review
Decision per gap	Each gap C1, #6, #7 has exactly one option labelled “Decision”
Cross-references	The three decisions reference each other where they interact (e.g., the trigger must respect nullable session_id)
Alternatives	≥ 3 alternatives per gap, each with a one-line tradeoff
Implementation	Names migration 007_post_finalize_guard.sql (or whatever the chosen number is) + lists each new column/trigger
Verification	A concrete grep / SQL / test-name check Sigma can run

Build / lint / test gate

npm run build && npm run lint && npm test must pass on the worktree. No source changes means tests should be untouched at 1357 (post-R83). Verification step will confirm.

Commit pattern (per CLAUDE.md §6)

Step	Commit prefix	Subject form
1	audit(adr-007-eta-session-lifecycle):	inventory surface
2	contract(adr-007-eta-session-lifecycle):	behavioral contract (this commit)
3	packet(adr-007-eta-session-lifecycle):	execution plan
4	feat(adr-007-eta-session-lifecycle):	propose ADR-007 η session lifecycle
5	verify(adr-007-eta-session-lifecycle):	test evidence

Five separate commits in worktree .worktrees/claude/adr-007-eta-session-lifecycle on branch feature/adr-007-eta-session-lifecycle.