fix(bedrock): emit contentBlockStart for all content block types in non-streaming mode#1849
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Friendly ping — CI is green, tests pass, rebased on latest. Ready for review whenever convenient. Happy to address any feedback. 🙏 |
…on-streaming mode In non-streaming mode (streaming=False), contentBlockStart events were only emitted for toolUse content blocks. Text, reasoning, and citation content blocks went straight to contentBlockDelta without a preceding contentBlockStart event. This broke parity with streaming mode where Bedrock itself sends contentBlockStart for every content block type, and caused consumers iterating stream_async events to miss contentBlockStart events for non-tool-use content. Now emit contentBlockStart with contentBlockIndex for all content block types (text, reasoningContent, citationsContent, toolUse) to match streaming behavior. Fixes strands-agents#1460
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Problem
In non-streaming mode (
streaming=False),contentBlockStartevents are only emitted fortoolUsecontent blocks. Text, reasoning, and citation content blocks go straight tocontentBlockDeltawithout a precedingcontentBlockStartevent.This breaks consumers that iterate over
stream_asyncevents expecting a consistent event sequence matching Bedrock's streaming API:Instead, non-streaming mode produces:
Root Cause
In
_stream_non_streaming(), thecontentBlockStartevent was gated behindif "toolUse" in content. Text, reasoning, and citation blocks skipped this gate and went directly tocontentBlockDelta.Fix
Emit
contentBlockStartwithcontentBlockIndexfor all content block types (text, reasoningContent, citationsContent, toolUse) to match streaming behavior where Bedrock itself sendscontentBlockStartfor every content block.Tests
contentBlockStarteventsFixes #1460