1 Commits

Author	SHA1	Message	Date
YeonGyu-Kim	524edb2b2e	fix: #164 Stage A — cooperative cancellation via cancel_event in submit_message ... Closes the #161 follow-up gap identified in review: wall-clock timeout bounded caller-facing wait but did not cancel the underlying provider thread, which could silently mutate mutable_messages / transcript_store / permission_denials / total_usage after the caller had already observed stop_reason='timeout'. A ghost turn committed post-deadline would poison any session that got persisted afterwards. Stage A scope (this commit): runtime + engine layer cooperative cancel. Engine layer (src/query_engine.py): - submit_message now accepts cancel_event: threading.Event | None = None - Two safe checkpoints: 1. Entry (before max_turns / budget projection) — earliest possible return 2. Post-budget (after output synthesis, before mutation) — catches cancel that arrives while output was being computed - Both checkpoints return stop_reason='cancelled' with state UNCHANGED (mutable_messages, transcript_store, permission_denials, total_usage all preserved exactly as on entry) - cancel_event=None preserves legacy behaviour with zero overhead (no checkpoint checks at all) Runtime layer (src/runtime.py): - run_turn_loop creates one cancel_event per invocation when a deadline is in play (and None otherwise, preserving legacy fast path) - Passes the same event to every submit_message call across turns, so a late cancel on turn N-1 affects turn N - On timeout (either pre-call or mid-call), runtime explicitly calls cancel_event.set() before future.cancel() + synthesizing the timeout TurnResult. This upgrades #161's best-effort future.cancel() (which only cancels not-yet-started futures) to cooperative mid-flight cancel. Stop reason taxonomy after Stage A: 'completed' — turn committed, state mutated exactly once 'max_budget_reached' — overflow, state unchanged (#162) 'max_turns_reached' — capacity exceeded, state unchanged 'cancelled' — cancel_event observed, state unchanged (#164 Stage A) 'timeout' — synthesised by runtime, not engine (#161) The 'cancelled' vs 'timeout' split matters: - 'timeout' is the runtime's best-effort signal to the caller: deadline hit - 'cancelled' is the engine's confirmation: cancel was observed + honoured If the provider call wedges entirely (never reaches a checkpoint), the caller still sees 'timeout' and the thread is leaked — but any NEXT submit_message call on the same engine observes the event at entry and returns 'cancelled' immediately, preventing ghost-turn accumulation. This is the honest cooperative limit in Python threading land; true preemption requires async-native provider IO (future work, not Stage A). Tests (29 new tests, tests/test_submit_message_cancellation.py + tests/ test_run_turn_loop_cancellation.py): Engine-layer (12 tests): - TestCancellationBeforeCall (5): pre-set event returns 'cancelled' immediately; mutable_messages, transcript_store, usage, permission_denials all preserved - TestCancellationAfterBudgetCheck (1): cancel set mid-call (after projection, before commit) still honoured; output synthesised but state untouched - TestCancellationAfterCommit (2): post-commit cancel not observable (honest limit) BUT next call on same engine observes it + returns 'cancelled' - TestLegacyCallersUnchanged (3): cancel_event=None preserves #162 atomicity + max_turns contract with zero behaviour change - TestCancellationVsOtherStopReasons (2): cancel precedes max_turns check; cancel does not retroactively override a completed turn Runtime-layer (5 tests): - TestTimeoutPropagatesCancelEvent (3): submit_message receives a real Event object when deadline is set; None in legacy mode; timeout actually calls event.set() so in-flight threads observe at their next checkpoint - TestCancelEventSharedAcrossTurns (1): same event object passed to every turn (object identity check) — late cancel on turn N-1 must affect turn N Regression: 3 existing timeout test mocks updated to accept cancel_event kwarg (mocks that previously had signature (prompt, commands, tools, denials) now have (prompt, commands, tools, denials, cancel_event=None) since runtime passes cancel_event positionally on the timeout path). Full suite: 97 → 114 passing, zero regression. Closes ROADMAP #164 Stage A. What's explicitly NOT in Stage A: - Preemptive cancellation of wedged provider IO (requires asyncio-native provider path; larger refactor) - Timeout on the legacy unbounded run_turn_loop path (by design: legacy callers opt out of cancellation entirely) - CLI exposure of 'cancelled' as a distinct exit code (currently 'cancelled' maps to the same stop_reason != 'completed' break condition as others; CLI surface for cancel is a separate pinpoint if warranted)	2026-04-22 18:14:14 +09:00