Fix bounded Codex cancellation terminal settlement (#188)

[Niko4417]

Scope

• Accepted issue: Closes Defect: Complete turn cancellation within the 5 s terminal bound #188
• Accepted planning-contract version: v1
• Automated readiness record: fingerprint 2fdaac328a268101b50a0ae5a7b91e168678db7ea3eddef84ce5c195dc934b7c
• Actual source branch: codex/188-cancellation-terminal
• Accepted target branch: epic/98-codex-tracer
• Parent epic and Quality Envelope rows: Epic: Governed Codex lifecycle tracer — one workspace, one no-effect turn #98; cancellation, lifecycle correctness, containment, accessibility, performance, resource cleanup, macOS packaged evidence
• Change classification: defect
• Product decision, finding, or incident: accepted cancellation could race runtime completion and leave the UI in stopping until the 5 s observer expired.
• In scope: authoritative terminal publication, cancellation/containment progression, a bounded projection reserve, truthful packaged terminal classification, and adjacent regression coverage.
• Out of scope: timeout increases, workspace performance, runtime upgrades, effects, replay/resume, Knowledge, Epic: Contract-as-Code migration and lifecycle activation cutover (ADR-0003/ADR-0004) #49, or broad lifecycle refactoring.
• Native targets, contracts, or trust boundaries affected: Keiko application lifecycle, macOS host runtime cleanup, frontend port state machine, and the packaged AX cancellation observer. Keiko remains the only terminal-state authority and signals remain confined to authenticated owned process groups.

Product and architecture alignment

• The implemented contract version and fingerprint match the automated readiness record; no semantic planning change was absorbed during implementation.
• The change follows the Decision Addendum, CONTEXT.md, accepted ADRs, and the issue Quality Plan.
• Existing Keiko material was used only after a recorded Reuse Assessment, or the issue records why Existing Keiko evidence is not applicable.
• This greenfield change creates no mandatory build-time or runtime dependency on Existing Keiko.
• Product authority, policy, evidence, and privileged effects remain in their owning Native layer.
• Any durable architecture change is recorded in an ADR.

Acceptance criteria and evidence

Acceptance criterion	Evidence	Exact head or artifact	Result
AC1	Deterministic host/frontend/AX regressions establish exactly one truthful cancelled, cleanup-failed, or containment-failed terminal and reserve 500 ms inside the unchanged 5 s public bound	b9890408cdc0e57548c33f229e0cffa237f0d177	Passed locally; packaged repetition pending #187 integration
AC2	Failure-first tests reproduced raced Completed publication, rejected stopping -> containment-failed, mixed terminal observation, and the unreserved 5 s cleanup allocation	b9890408cdc0e57548c33f229e0cffa237f0d177	Passed
AC3	Rust 162/162, frontend 58/58, AX 13/13, plus independent lifecycle/containment audit	b9890408cdc0e57548c33f229e0cffa237f0d177	Passed
AC4	Complete quality, npm audit, macOS package build, target tests, exact audit	b9890408cdc0e57548c33f229e0cffa237f0d177	Local gates passed; final canonical packaged journey pending #187

Acceptance journey evidence

• Applicability: Required

Journey and checkpoint	Automated evidence and command	Manual or platform evidence	Result
Cancel streamed no-effect turn	Rust/frontend/AX failure-first and focused suites; npm run quality	Packaged macOS arm64 binary built and authenticated at exact head	Automated passed; repeated canonical journey pending #187
Truthful containment or cleanup failure	Host precedence, frontend progression, and one-traversal AX classification regressions	Semantic terminal remains failure, never cancellation success	Passed
Zero residue and late-event rejection	Existing authenticated cleanup, identity, quarantine, and recovery neighbors plus exact native target suite	Final repeated physical receipt pending	Automated passed

• Automated checks exercise user-visible outcomes rather than incidental implementation details.
• Required failure, recovery, accessibility, visual, and platform observations are settled.

Quality Plan settlement

• Applicable positive, negative, boundary, failure, cancellation, and recovery behavior is covered.
• The actually wired production composition was tested where this change crosses layers.
• Applicable security, accessibility, performance, resource, visual, and platform evidence is attached or linked.
• Excluded quality areas retain the rationale accepted in the issue.
• Secrets, credentials, raw customer content, private endpoints, and PII are absent from source, tests, logs, evidence, artifacts, issues, and this pull request.

Verification

• npm ci --ignore-scripts
• npm run quality
• npm audit --audit-level=high
• Every declared native target-specific gate passed on its authoritative platform.
• I reviewed the complete diff against requirements, contracts, trust boundaries, and failure modes.

Additional affected checks and concise results:

Exact local head b9890408cdc0e57548c33f229e0cffa237f0d177
npm run quality: passed
npm audit --audit-level=high: 0 vulnerabilities
npm run acceptance:macos: passed; exact macOS arm64 package built
cargo +1.92.0 test --locked --manifest-path native/Cargo.toml -p keiko-application -p keiko-host-macos: 20 + 162 passed
Focused frontend: 58/58
Focused AX source/runner: 13/13 including macOS source compilation
git diff --check: passed

Independent audit and findings

• Audit scope and dimensions: terminal ownership and precedence; cancel/completion/timeout races; authenticated cleanup and deadline arithmetic; frontend composition; AX semantic classification; redaction; package exclusion; exact scope and signatures.
• Audited commit: b9890408cdc0e57548c33f229e0cffa237f0d177

Confirmed finding	Evidence	Disposition	Settlement evidence or follow-up
stopping -> containment-failed was rejected by the renderer	Real port reproduction and regression	Resolved	7b627d7b69b2b54a8b81d39f33e5b337fc343a51
Runtime cleanup could consume the full public terminal budget	Deterministic allocation seam	Resolved	5b290e82aea30d3c308eb26c1949a18c8b55d76c, 4fada798f2370840d68ae4a04ca8f5a9ddeab48d
Packaged observer obscured cleanup/containment terminals	Failure-first AX classifier regressions	Resolved	b9890408cdc0e57548c33f229e0cffa237f0d177

• Findings are evidence-cited; speculative observations are advisory rather than blockers.
• Every confirmed finding is resolved, explicitly accepted by an authorized human, or linked to a scoped follow-up that does not invalidate current acceptance.
• Verification and audit were repeated after the latest implementation or audit fix.

Integrated epic acceptance

• Applicability: Required
• Production-composition result: exact application/host/frontend/AX composition is covered and locally green.
• Machine-enforced acceptance result: complete local quality and audit are green.
• macOS evidence: exact package build passed; canonical Codex journey will be repeated after Defect: Correct successful workspace projection boundary #187 removes its accepted measurement blocker.
• Windows evidence: not applicable; accepted target is macOS arm64.
• Manual usability, accessibility, visual, signing, or packaging evidence: final physical cancellation/VoiceOver/keyboard/zero-residue receipt pending the rebased canonical journey.

Delivery

• Target path: child issue -> epic branch
• The target branch matches the delivery path accepted in the issue; no direct push, force push, gate bypass, finding dismissal, or authority widening occurred.
• Commits are signed and every completed check is bound to the exact current head and expected producer.
• Advisory tools are not treated as required merge authority under the current quality-gate policy.
• Documentation, ADRs, contracts, known limitations, and follow-ups are current.
• A draft pull request was not promoted to Ready for Human Review before every required Acceptance Journey result and exact-head gate was complete.

For a child-issue pull request targeting its designated epic branch:

• The accepted issue authorizes this epic-branch target.
• Acceptance and audit evidence is complete, every applicable exact-head gate is green, and no blocking finding or review conversation remains.

Residual risks and follow-ups

• The final Integrated packaged macOS acceptance for the Codex tracer #104 canonical packaged journey is intentionally pending accepted sibling Defect: Correct successful workspace projection boundary #187 because its current AX measurement boundary is independently known to be invalid. No Defect: Complete turn cancellation within the 5 s terminal bound #188 budget or terminal criterion is weakened.

[Niko4417]

@codex review