feat(ui): Ctrl-C cancels a model turn mid-stream#12
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In the full-screen app a long turn was a blind wait with no escape. Add a clean turn-abort: Ctrl-C (a key press now — raw mode disables ISIG, so it is not a SIGINT) sets a per-turn cancel Event; the Ollama stream checks it at each read boundary and raises a typed GenerationCancelled, closing the response in-thread via the stream context manager. The exception is neither an OllamaError nor an httpx error, so the think-retry and the transport handler leave it alone and it propagates cleanly. History stays intact: the model call sits in a try/finally that only closes the UI response; the reply is recorded after it, so a cancelled turn skips the record site and never stores a truncated partial — the user message stands, the aborted reply is discarded. The worker tells a cancel apart from a failure: GenerationCancelled routes to a clean abort_turn (clear the thinking indicator, mark the partial '⏹ aborted'), any other exception is a pane error, and the busy flag clears on every path so a cancel never wedges the app. The cancel Event is passed to the worker as a thread argument (a captured local), so the worker never reads the mutable instance attribute and the loop-thread-only invariant holds. cancel defaults to None on every hop, so the default REPL and non-TTY paths are byte-identical. Cancelling a running subprocess (killpg) is a follow-up; today a cancel during a command aborts the turn once the command returns. DESIGN.md §31.15 added.
lavindeep
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Jul 2, 2026
feat(ui): Ctrl-C cancels a model turn mid-stream
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Branch 6/9 of the UI v2 rework (model-stream cancellation). A long turn was a blind wait with no escape; now Ctrl-C aborts it cleanly.
What
Event.OllamaClient._stream_chatchecks the event at each read boundary and raises a typedGenerationCancelled, closing the response in-thread via thewith self._client.stream(...)context manager (the only cross-thread op isEvent.set()). The exception is neitherOllamaErrornor an httpx error, so the think-retry and transport handler don't swallow it.try/finallythat only closes the UI response;_record(reply)is after it, so a cancelled turn skips the record site — the user message stands, the partial reply is never stored.GenerationCancelled→ cleanabort_turn(clear indicator, mark⏹ aborted); other exceptions → pane error;_mark_doneclears busy on every path (no wedge). The cancel event is passed as a thread argument so the worker never reads the mutableself._cancel(invariant holds literally).Scope
Subprocess
killpgis branch 6b — a cancel during a running command aborts the turn once the command returns. No approval/queue (branches 7/9).Verification
mypy --strict, 1368 passed.canceldefaults toNoneeverywhere → default REPL + non-TTY byte-identical. DESIGN §31.15 in the same commit.⏹ aborted, indicator clears, next turn works.