Spec Kitty

Tasks: Fail-closed acceptance-matrix merge driver (#4880)

Mission: acceptance-matrix-merge-fail-closed-01M34HG8 Branch: fix/acceptance-matrix-merge-fail-closed Plan: plan.md · Spec: spec.md

Small brownfield fix. Four work packages: three code_change, one planning_artifact (the code-vs-planning ownership split is mandatory). WP03 and WP04 depend on WP01 (the mechanism must raise before the tests expect refusal and before the decision docs describe the landed behavior). WP02 is independent and parallel.

Subtask Index

ID	Description	WP	Parallel
T001	_merge_field raises RowMatrixMergeError on the both-sides-diverged branch (was _field_conflict_marker at :424)	WP01
T002	Delete the now-unreachable _field_conflict_marker function ONLY (KEEP the _CONFLICT_MARKER_* constants — used by the review-cycle driver)	WP01
T003	Broaden both matrix drivers' except to also catch AcceptanceMatrixParseError → Exit(1)	WP01
T004	Confirm both drivers surface Exit(1) and _merge_branch_into aborts	WP01
T005	AcceptanceMatrix.from_dict rejects any value containing a conflict marker → AcceptanceMatrixParseError	WP02	[P]
T006	Focused test for the read-side marker-reject guard	WP02	[P]
T007	Red-first proof: the three pins assert marker-embed against the pre-fix product file	WP03
T008	Re-anchor the three genuine-conflict pins to expect refusal	WP03
T009	Keep controls green; confirm no distinct FR-004 negative-control green-pins the flip (post_consolidation is a red herring — do not edit)	WP03
T014	CLI-entry refusal test: merge_driver_acceptance_matrix exits non-zero on a both-sides conflict (FR-002/SC-001)	WP03
T010	Amend ADR 2026-07-23-2: qualify "no consolidation abort" to exclude gate/verdict artifacts	WP04	[P]
T011	Amend contract merge-driver-algorithm.md:29 per the amendment note	WP04	[P]
T012	Amend 01KZPG7V spec FR-004 note (superseded → fail-closed)	WP04	[P]
T013	Consumer-facing changelog entry	WP04	[P]

Work Packages

WP01 — Fail-closed mechanism (merge_driver.py) [code_change]

• Goal: Close the corruption class by construction — _merge_field raises instead of embedding markers; delete the embed path; harden the drivers' except.
• Priority: P1 (the fix). Dependencies: none.
• Independent test: a both-sides-diverged field now raises RowMatrixMergeError; _field_conflict_marker is gone.
• Subtasks: T001, T002, T003, T004
• Requirements: FR-001, FR-002, FR-005, NFR-002, NFR-003
• Prompt: tasks/WP01-failclosed-mechanism.md (~180 lines)

WP02 — Read-side marker-reject guard (matrix.py) [code_change] [P]

• Goal: Defense-in-depth — from_dict rejects marker-laden values loudly instead of recomputing to fail.
• Priority: P2. Dependencies: none (parallel with WP01; different module).
• Independent test: a matrix dict with a marker string in a field raises AcceptanceMatrixParseError.
• Subtasks: T005, T006
• Requirements: FR-004, NFR-001
• Prompt: tasks/WP02-read-guard.md (~150 lines)

WP03 — Red-first + re-anchor the divergence pins [code_change]

• Goal: Prove the fix witnesses the bug; re-anchor the three tests that green-pin the corruption to expect refusal.
• Priority: P1. Dependencies: WP01.
• Independent test: each pin fails against the pre-fix product file and passes (expecting refusal) after WP01.
• Subtasks: T007, T008, T009, T014
• Requirements: FR-002, FR-003, NFR-001
• Prompt: tasks/WP03-redfirst-reanchor.md (~220 lines)

WP04 — Amend recorded decisions + changelog [planning_artifact]

• Goal: Land the decision reversal in the same change: ADR, contract, 01KZPG7V FR-004 note, consumer changelog.
• Priority: P1 (must land with the fix — C-003). Dependencies: WP01.
• Independent test: ADR/contract/FR-004 prose reflect fail-closed for verdict artifacts; changelog has a consumer-facing entry.
• Subtasks: T010, T011, T012, T013
• Requirements: FR-006, C-003, C-004
• Prompt: tasks/WP04-decision-amendments.md (~140 lines)

Dependency graph

WP01 ─┬─→ WP03   (tests expect the raise)
      └─→ WP04   (docs describe the landed behavior)
WP02  ── parallel (independent module)

MVP scope

WP01 is the load-bearing fix. WP01+WP03 together are the releasable minimum (fix + proof + re-anchored pins). WP02 (defense-in-depth) and WP04 (decision docs) land in the same PR per C-003.