Best possible solution:

Merge the narrow inventory update after exact-head required checks finish, then let the linked issue close through this PR or an equivalent landed fix.

Do we have a high-confidence way to reproduce the issue?

Yes. Source inspection gives a high-confidence reproduction: current main scans all bundled production plugin files for api.on(...) and compares them to an explicit list that omits Workboard, while Workboard registers api.on("subagent_ended"); I did not run tests in this read-only review.

Is this the best way to solve the issue?

Yes. The narrow inventory update is the best fix because the hook is valid and already intentional; removing the hook or weakening the invariant would either change Workboard cleanup behavior or reduce the contract test's value.

AGENTS.md: found and applied where relevant.

Codex review notes: model internal, reasoning high; reviewed against d5371395218c.

Label changes:

• add P2: The PR fixes a deterministic current-main plugin contract regression for contributor validation, but the diff is narrow and has no runtime behavior, data, auth, or message-delivery blast radius.
• add rating: 🐚 platinum hermit: Overall readiness is 🐚 platinum hermit; proof is 🌊 off-meta tidepool and patch quality is 🐚 platinum hermit.
• add status: 👀 ready for maintainer look: ClawSweeper has no concrete contributor-facing blocker left for this PR. Not applicable: This is a maintainer-labeled test-only PR, so the contributor real-behavior proof gate does not apply; the PR body still cites Testbox contract-test output for the changed check.

Label justifications:

• P2: The PR fixes a deterministic current-main plugin contract regression for contributor validation, but the diff is narrow and has no runtime behavior, data, auth, or message-delivery blast radius.
• rating: 🐚 platinum hermit: Overall readiness is 🐚 platinum hermit; proof is 🌊 off-meta tidepool and patch quality is 🐚 platinum hermit.
• status: 👀 ready for maintainer look: ClawSweeper has no concrete contributor-facing blocker left for this PR. Not applicable: This is a maintainer-labeled test-only PR, so the contributor real-behavior proof gate does not apply; the PR body still cites Testbox contract-test output for the changed check.

PR surface:

Tests +2. Total +2 across 1 file.

What I checked:

• Current-main inventory mismatch: The invariant test scans bundled production plugin files for api.on(...) and expects them to match BUNDLED_TYPED_HOOK_REGISTRATION_FILES, but current main's list does not include extensions/workboard/index.ts. (src/plugins/contracts/boundary-invariants.test.ts:15, d5371395218c)
• Workboard registers the missing hook: Workboard's bundled plugin entrypoint registers api.on("subagent_ended", ...) and uses the event run id for worktree cleanup, so the file is a real typed-hook registration source. (extensions/workboard/index.ts:17, d5371395218c)
• Hook name is a valid typed hook: subagent_ended is part of PluginHookName, appears in PLUGIN_HOOK_NAMES, and has a typed handler entry, so the PR is not allowing an unknown hook. (src/plugins/hook-types.ts:116, d5371395218c)
• PR diff is the narrow inventory update: The live diff adds only extensions/workboard/index.ts and the subagent_ended guard to the existing explicit allowlist; it does not touch runtime code, config, dependencies, or workflows. (src/plugins/contracts/boundary-invariants.test.ts:23, a38744f706e6)
• Regression provenance: Blame on the Workboard hook shows commit 0acd851a3b3d6142f1e569a0e5616db62361969e added the subagent_ended cleanup registration as part of the managed worktree lifecycle merge. (extensions/workboard/index.ts:17, 0acd851a3b3d)
• Contract inventory provenance: Blame on the typed-hook inventory constants points to d2d5911c3296dfa3cf368eff1acdd1f1ede844d7 as the current inventory source that needs the Workboard addition. (src/plugins/contracts/boundary-invariants.test.ts:15, d2d5911c3296)

Likely related people:

• steipete: Git blame ties both the Workboard subagent_ended registration and the current typed-hook inventory constants to Peter Steinberger, and the PR is also assigned to steipete. (role: introduced behavior and recent area contributor; confidence: high; commits: 0acd851a3b3d, d2d5911c3296; files: extensions/workboard/index.ts, src/plugins/contracts/boundary-invariants.test.ts)

• 🦀 challenger crab: rare, exceptional readiness with strong proof, clean implementation, and convincing validation.
• 🦞 diamond lobster: very strong readiness with only minor maintainer review expected.
• 🐚 platinum hermit: good normal PR, likely mergeable with ordinary maintainer review.
• 🦐 gold shrimp: useful signal, but proof or patch confidence is still limited.
• 🦪 silver shellfish: thin signal; proof, validation, or implementation needs work.
• 🧂 unranked krab: not merge-ready because proof is missing/unusable or there are serious correctness or safety concerns.
• 🌊 off-meta tidepool: rating does not apply to this item.

Shiny media proof means a screenshot, video, or linked artifact directly shows the changed behavior. Runtime, network, CSP, and security claims still need visible diagnostics.

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