fix(transcript_mirror): handle CancelledError in eager-flush done callback#931
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…lback The ``add_done_callback`` lambda on the eager-flush ``_flush_task`` called ``t.exception()`` unconditionally. In Python 3.8+, ``Task.exception()`` raises ``CancelledError`` for cancelled tasks, and the raise from inside a done-callback surfaces as a noisy "Exception in callback" log every time the SDK shuts down with pending eager flushes (visible in anthropics#928's failing-test traceback). Replace the lambda with a module-level ``_swallow_done_exception`` helper that no-ops on cancelled tasks and otherwise retrieves the exception so asyncio doesn't warn about an unretrieved exception on a fire-and-forget task. Closes anthropics#930 Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
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Summary
Fixes #930.
The
add_done_callbacklambda on the eager-flush_flush_taskcalledt.exception()unconditionally. In Python 3.8+,Task.exception()raisesCancelledErrorfor cancelled tasks, and the raise from inside a done-callback surfaces as a noisyException in callbacklog every time the SDK shuts down with pending eager flushes — visible in #928's failing-testCaptured log teardownblock.Changes
src/claude_agent_sdk/_internal/transcript_mirror_batcher.py: replacelambda t: t.exception()with a module-level_swallow_done_exceptionhelper that no-ops on cancelled tasks and otherwise retrieves the exception so asyncio doesn't warn.tests/test_transcript_mirror.py: addTestSwallowDoneExceptionwith three cases — cancelled task (must not raise), failed task (retrieves exception, doesn't re-raise), successful task (no-op).Test plan
uv run pytest tests/test_transcript_mirror.py::TestSwallowDoneException— 3 passeduv run mypy src/— cleanruff check / ruff format— cleanNotes
The fix is intentionally narrow — same call site, same intent (silence "Task exception was never retrieved" warnings), just cancellation-safe. No behavior change on the happy path.