fix(langchain): ensure message id consistency #11617
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lgrammel
approved these changes
Jan 8, 2026
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Background
openai's api can change the message ID during streaming when transitioning from reasoning to text. due to the changed IDs, the lookup returned undefined, causing the crash.
it led to the error seen in #11581
Summary
updated processModelChunk to track the IDs used for *-start events and use them consistently for all subsequent *-delta and *-end events:
Manual Verification
ui example added in
examples/next-langchain/app/reasoningwhich failed with the same error seen in original issue, was resolved after fixChecklist
pnpm changesetin the project root)Related Issues
Fixes #11581