fix(ui): rebuild partialToolCalls on resume for input-streaming tool parts#14255
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giulio-leone wants to merge 1 commit intovercel:mainfrom
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fix(ui): rebuild partialToolCalls on resume for input-streaming tool parts#14255giulio-leone wants to merge 1 commit intovercel:mainfrom
giulio-leone wants to merge 1 commit intovercel:mainfrom
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…parts When createStreamingUIMessageState receives a lastMessage containing tool parts in input-streaming state, the partialToolCalls map was initialized as empty. This caused tool-input-delta chunks during resume to fail because the lookup for the existing tool call returned undefined. The fix reconstructs partialToolCalls entries from any existing input-streaming tool parts in the lastMessage, enabling resumed streams to continue appending deltas to in-progress tool calls. Fixes vercel#14027 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Summary
Fixes #14027
When
createStreamingUIMessageStatereceives alastMessagecontaining tool parts ininput-streamingstate (e.g. duringresumeStream()), thepartialToolCallsmap was initialized as{}. This caused subsequenttool-input-deltachunks to fail because the lookup for the existing tool call returnedundefined, throwing:Root Cause
createStreamingUIMessageStatenever reconstructedpartialToolCallsfrom existinginput-streamingtool parts in the providedlastMessage. Fresh streams work fine because they always start withtool-input-start, but resumed streams skip that chunk since the tool part already exists in the hydrated message.Fix
After constructing the message, iterate over any existing tool parts in
input-streamingstate and pre-populatepartialToolCallswith their current state (serialized input text, index, tool name, dynamic flag, title). This enables the stream processor to correctly handletool-input-deltachunks during resume.Changes
packages/ai/src/ui/process-ui-message-stream.ts— RebuildpartialToolCallsincreateStreamingUIMessageStatefrom existinginput-streamingtool partspackages/ai/src/ui/process-ui-message-stream.test.ts— Add regression tests for resuming both static and dynamic tool parts ininput-streamingstateTests
96/96 tests pass (
vitest run --config vitest.node.config.js src/ui/process-ui-message-stream.test.ts), including 2 new regression tests.