fix(workflow): drop orphan UI chunks after non-zero startIndex reconnect#15543
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fix(workflow): drop orphan UI chunks after non-zero startIndex reconnect#15543VaguelySerious wants to merge 2 commits into
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When `WorkflowChatTransport` resumes with a non-zero `initialStartIndex`, the resolved chunk can land in the middle of an open `text-*` / `reasoning-*` / `tool-input-*` part. AI SDK's client enforces the start→delta→end grammar and throws on the orphan delta, breaking the chat. Add a one-pass filter on the resumed stream that drops chunks referencing a part whose start chunk wasn't in the resumed window, and warn once with a pointer to docs on server-side rewinding. Filter only activates for non-zero startIndex — startIndex 0 replays from the beginning and is always safe. Refs: vercel/workflow#1835 Ports vercel/workflow#2082 to @ai-sdk/workflow. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
![vercel[bot]](https://avatars.githubusercontent.com/in/8329?s=60&v=4){kind=small}
…ol-output-denied` and `tool-approval-request` chunk types, causing `UIMessageStreamError` crashes when resuming a stream mid-part. This commit fixes the issue reported at packages/workflow/src/workflow-chat-transport.ts:76 **Bug explanation:** The `createOrphanFilter()` function in `workflow-chat-transport.ts` is designed to prevent crashes when a stream resume lands mid-part — it drops chunks that reference a `toolCallId` whose `tool-input-start` was emitted before the resume window. The filter correctly handles these tool chunk types against `seenStartedToolCallIds`: - `tool-input-delta` - `tool-input-available` - `tool-input-error` - `tool-output-available` - `tool-output-error` But it's missing two chunk types that also use `toolCallId`: - `tool-approval-request` — calls `getToolInvocation(chunk.toolCallId)` at line 705 of `process-ui-message-stream.ts` - `tool-output-denied` — calls `getToolInvocation(chunk.toolCallId)` at line 742 of `process-ui-message-stream.ts` Both types have a `toolCallId` field (confirmed in `ui-message-chunks.ts` schema and type definitions). When `getToolInvocation()` is called with a `toolCallId` that has no matching tool invocation (because the `tool-input-start` was before the resume window), it throws a `UIMessageStreamError` with message `No tool invocation found for tool call ID`. This is exactly the crash scenario the orphan filter was designed to prevent. This would manifest when: 1. A tool call involves an approval flow (using `tool-approval-request`) or denial (`tool-output-denied`) 2. The stream is interrupted and resumed 3. The resume position lands after the `tool-input-start` but before/at the `tool-approval-request` or `tool-output-denied` chunk **Fix explanation:** Added `case 'tool-approval-request':` and `case 'tool-output-denied':` to the switch statement's tool-related branch that checks `seenStartedToolCallIds`. These fall through to the same logic as the other tool chunk types — if the `toolCallId` was seen in a `tool-input-start`, the chunk is kept; otherwise it's dropped with a warning. This is consistent with how all other `toolCallId`-based chunks are handled. Co-authored-by: Vercel <vercel[bot]@users.noreply.github.com> Co-authored-by: VaguelySerious <mittgfu@gmail.com>
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Summary
When
WorkflowChatTransportresumes with a non-zeroinitialStartIndex(positive or negative), the resolved chunk index can land in the middle of an opentext-*/reasoning-*/tool-input-*part. AI SDK's client enforces the*-start → *-delta → *-endgrammar and throws on the orphan delta — breaking the chat.This PR adds a one-pass filter on the resumed stream that drops chunks referencing a part whose start chunk wasn't in the resumed window, and emits a one-time warning pointing at docs on server-side rewinding. The filter only activates when
useExplicitStartIndexis true —startIndex: 0replays from the beginning and is always safe.Reported and reproduced in vercel/workflow#1835. This is the port of the corresponding fix in vercel/workflow#2082 to
@ai-sdk/workflow.Changes
packages/workflow/src/workflow-chat-transport.ts: addcreateOrphanFilter()and wire into the reconnect iterator.packages/workflow/src/workflow-chat-transport.test.ts: 6 new tests covering orphan reasoning / text / tool-input chunks, the pass-through path, positive-startIndex activation, and the startIndex-0 skip path..changeset/orphan-ui-chunks-on-resume.md: patch bump for@ai-sdk/workflow.Test plan
pnpm test:nodepasses (125 tests, 6 new)pnpm test:edgepasses (125 tests, 6 new)pnpm type-checkpassespnpm check(lint/format) clean