feat(workflow): export WorkflowChatTransport with stream reconnection support#14340
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gr2m merged 4 commits intogr2m/durable-agentfrom Apr 11, 2026
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feat(workflow): export WorkflowChatTransport with stream reconnection support#14340gr2m merged 4 commits intogr2m/durable-agentfrom
gr2m merged 4 commits intogr2m/durable-agentfrom
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…upport Export WorkflowChatTransport as a public API from @ai-sdk/workflow. Add initialStartIndex option for resuming streams from the tail (negative values), with x-workflow-stream-tail-index header resolution and graceful fallback. Extract getErrorMessage utility for proper error formatting in reconnection failures. Update next-workflow example to use the transport. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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When a positive startIndex is used, set chunkIndex to match so that retries after disconnection resume from the correct position instead of restarting from 0. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Add /test page and mock /api/test-chat endpoints that simulate stream interruption. The POST route sends a partial stream (no finish event), forcing the transport to reconnect via the GET stream endpoint. The transport log panel shows the full lifecycle: POST -> streaming -> reconnect -> Chat ended. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
- Add API reference page for WorkflowChatTransport with constructor parameters, methods, reconnection flow, server requirements, and usage examples - Add WorkflowChatTransport card to workflow reference index - Add "Resumable Streaming" section to WorkflowAgent guide with client and server endpoint examples - Add "Workflow Transport" section to the transport guide page - Add link to WorkflowChatTransport reference in Next Steps Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Background
The
WorkflowChatTransportclass was implemented in@ai-sdk/workflowbut not exported, making it unavailable to consumers. This transport is needed foruseChatto enable automatic stream reconnection in workflow-based chat apps — handling network failures, page refreshes, and function timeouts by reconnecting to the workflow's stream endpoint.Reference: DurableChatTransport
Summary
WorkflowChatTransportclass and related types (WorkflowChatTransportOptions,SendMessagesOptions,ReconnectToStreamOptions) from@ai-sdk/workflowinitialStartIndexoption for resuming streams from the tail (negative values like-50fetch only the last 50 chunks, useful for page refresh recovery without replaying the full conversation)x-workflow-stream-tail-indexheader resolution to compute absolute chunk positions from negative start indices, with graceful fallback to replay-from-start when the header is missingstartIndexreconnection: setchunkIndexto match the explicit start position so retries after disconnection resume correctlystartIndexper-call override onReconnectToStreamOptionsgetErrorMessageutility for proper error formatting in reconnection failures (avoids[object Object]in error messages)examples/next-workflowmain page to useWorkflowChatTransportwithuseChatexamples/next-workflow/testpage with mock API routes that simulate stream interruption and verify reconnection recovery end-to-endDocumentation
WorkflowChatTransportreference page atdocs/reference/ai-sdk-workflow/workflow-chat-transportwith constructor parameters, methods, reconnection flow, server requirements, and examplesWorkflowChatTransportcardManual Verification
examples/next-workflowdev server (pnpm next dev)/): Sent "What is the weather in San Francisco?" — WorkflowAgent calledgetWeathertool, responded with "86°F and windy". Sent "What is 42 * 17?" — calledcalculatetool, responded "714". Both messages usedWorkflowChatTransport./test): The test page uses mock API routes where the POST endpoint sends only 2 of 6 SSE chunks (nofinishevent), simulating a function timeout. The transport detected the missingfinishchunk, automatically reconnected via GET to/api/test-chat/{runId}/stream?startIndex=2, received the remaining chunks, and displayed the complete message. The transport log panel confirmed the full lifecycle:POST response received(onChatSendMessagecallback fired)Status: streaming(partial stream consumed)Chat ended: total chunks=6(onChatEndcallback fired)Status: readyChecklist
pnpm changesetin the project root)Related Issues
Follow-up to #12165