Risky behavior now covered

• Task policy (extracted from TaskCoordinator): terminal tasks cannot be mutated or grow new threads; pending terminal locks fail closed unless the caller opts in; revision conflicts name both sides; workspace mismatch is rejected; work-item graphs reject duplicates, unknown edges, self-edges, and cycles; only the owning or primary thread can mark an unclaimed item; claims and dependency-gated statuses require completed dependencies; incomplete dependencies cannot be removed.
• Workflow structured output: extractResultEnvelope keeps the last <workflow_result> block, treats empty/missing bodies as absent, and still yields an unclosed final block. validateAgainstJsonSchema reports missing/invalid JSON and path-qualified schema issues without throwing, and throws for a malformed caller schema so a repair turn is not wasted.
• Thread management request schemas: thread/fork trims ids and worktree refs, accepts local / worktree, and rejects blanks, extras, unknown environment types, and local extras. Pin/archive require a real boolean and reject blanks or extras.

Test files added

• test/server/tasks/taskPolicy.test.ts
• test/workflows/resultSchema.test.ts
• test/jsonrpc.thread-management-schema-rejects.test.ts

Why these tests reduce regression risk

These are shared fail-closed gates with a large blast radius. The recent TaskCoordinator extraction left taskPolicy.ts as the authority for ownership, graph, and terminal-lock checks with no dedicated tests. Workflow envelope validation was only exercised through runner happy paths, so a parse/repair regression could accept invalid child output or burn repair turns. Thread fork/pin/archive schemas had integration happy paths only; a loosened environment union or optional boolean would let clients create or mutate threads with invalid params.

This run does not duplicate open coverage PRs #331, #332, or #333.

Validation

• Targeted new files + platform-boundary: 29 tests green
• Related existing task/workflow tests: 69 green
• bun run typecheck, bun run check, bun run docs:check, and Biome on touched files: clean
• Full bun run test: new files that reached the runner passed in-suite (taskPolicy, thread-management-schema-rejects). resultSchema passed isolated; the host suite truncated before test/workflows/* (same pattern as recent coverage runs). Reproduced the known ipc-files rewritten-mtime reauth failure; not introduced by this change.