fix(streaming): validate content_block_start index before appending#1690
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WalkingDreams798 wants to merge 1 commit into
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fix(streaming): validate content_block_start index before appending#1690WalkingDreams798 wants to merge 1 commit into
WalkingDreams798 wants to merge 1 commit into
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`accumulate_event` appended each `content_block_start` block to the snapshot without checking `event.index`, silently relying on blocks arriving in order (this was the long-standing `# TODO: check index`). An out-of-order or skipped index would corrupt the snapshot — later `content_block_delta`/`content_block_stop` events index into the wrong block or raise an opaque IndexError. Validate that `event.index == len(current_snapshot.content)` and raise a clear RuntimeError on mismatch, matching the existing "Unexpected event order" style. Applied to both the standard and beta accumulators, with unit tests covering sequential appends and the mismatch error.
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What
accumulate_event(in bothlib/streaming/_messages.pyand_beta_messages.py) appended eachcontent_block_startblock to the snapshot without checkingevent.index— it silently relied on blocks arriving strictly in order. This was the long-standing# TODO: check indexin both files.If a
content_block_startever arrived with an out-of-order or skipped index, the block would land at the wrong position incurrent_snapshot.content, and subsequentcontent_block_delta/content_block_stopevents (which index byevent.index) would mutate the wrong block or raise an opaqueIndexError.Change
Validate that
event.index == len(current_snapshot.content)before appending, and raise a clearRuntimeErroron mismatch — consistent with the existing'Unexpected event order, got ... before "message_start"'style already used in the same function.Applied identically to the standard and beta accumulators, resolving both TODOs.
Tests
Added
tests/lib/streaming/test_content_block_index.pycovering, for both the standard and beta paths:RuntimeErrorVerification
uv run pytest tests/lib/streaming→ 44 passeduv run ruff check→ all checks passeduv run pyright(strict) on changed files → 0 errors, 0 warnings