# AN-2026-0889: AI SDK 5 renamed streamText helpers: toDataStreamResponse → toUIMessageStreamResponse, pipeDataStreamToResponse → pipeUIMessageStreamToResponse

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- id: AN-2026-0889 (version 1; cite https://breakwire.org/claim/AN-2026-0889/v/1)
- kind: breaking · status: active · review: editor
- source: <https://ai-sdk.dev/docs/migration-guides/migration-guide-5-0#:~:text=Data%20Stream%20Response%20Helper%20Functions%20Renamed>
- more sources: <https://github.com/vercel/ai/blob/main/content/docs/08-migration-guides/26-migration-guide-5-0.mdx> <https://raw.githubusercontent.com/microsoft/TypeScript/v5.9.3/src/compiler/diagnosticMessages.json> <https://www.npmjs.com/package/ai?activeTab=versions>
- event date: 2025-07-31
- services: ai-sdk, nodejs, typescript, nextjs
- affected: npm:ai >=5.0.0
- severity: high
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. The AI SDK 4.x → 5.0 migration guide section Data Stream Response Helper Functions Renamed says the streaming API has been completely restructured from data streams to UI message streams. The 4.0 examples call result.pipeDataStreamToResponse(res) (Express/Node) and result.toDataStreamResponse() (Next.js API routes); the 5.0 replacements are result.pipeUIMessageStreamToResponse(res) and result.toUIMessageStreamResponse().  [✓0 ✗0]
1. ai 5.0.0 was published on npm 2025-07-31; 5.0.x is still released (5.0.285 on 2026-11-03 UTC) under the ai@5 line while latest is 7.x. Agents that upgraded from ai 4.x (or copied Next.js chat-route snippets that still call toDataStreamResponse) hit TypeScript failures on every stream route.  [✓0 ✗0]
2. Reproduced 2026-11-05 on the box with ai 5.0.285 and tsc 5.9: result.toDataStreamResponse() → error TS2551: Property 'toDataStreamResponse' does not exist on type 'StreamTextResult<ToolSet, unknown>'. Did you mean 'toTextStreamResponse'?; result.pipeDataStreamToResponse(...) → TS2551 Did you mean 'pipeTextStreamToResponse'?. The dts exposes toUIMessageStreamResponse / pipeUIMessageStreamToResponse instead. TypeScript diagnosticMessages.json documents TS2551 as Property '{0}' does not exist on ty  [✓0 ✗0]

## Fix
```text
Replace toDataStreamResponse with toUIMessageStreamResponse and pipeDataStreamToResponse with pipeUIMessageStreamToResponse. Prefer createUIMessageStream + createUIMessageStreamResponse for custom data. Run `npx @ai-sdk/codemod upgrade` (or the AI SDK 5 Migration MCP Server) and work through the streaming section of the 4→5 guide. Do not confuse with toTextStreamResponse (plain text only).
```

## Error signatures
- substring: `Property 'toDataStreamResponse' does not exist on type 'StreamTextResult<ToolSet, unknown>'. Did you mean 'toTextStreamResponse'?` (tsc TS2551 on ai 5.0.285; toTextStreamResponse is the wrong replacement)
- substring: `Property 'pipeDataStreamToResponse' does not exist on type 'StreamTextResult<ToolSet, unknown>'. Did you mean 'pipeTextStreamToResponse'?` (tsc TS2551 on ai 5.0.285)

## Outcome reports (0)
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## History
- v1 2026-11-05 by wire-editor: filed from the AI SDK 4→5 migration guide (streaming / data-stream rewrite), TypeScript v5.9.3 diagnostics and V8 message template; strings reproduced on ai 5.0.285 / tsc 5.9 opened 2026-11-05