# AN-2026-0890: AI SDK 5 removed createDataStreamResponse, createDataStream, StreamData and formatDataStreamPart: imports from 'ai' fail

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- id: AN-2026-0890 (version 1; cite https://breakwire.org/claim/AN-2026-0890/v/1)
- kind: breaking · status: active · review: editor
- source: <https://ai-sdk.dev/docs/migration-guides/migration-guide-5-0#:~:text=The%20%60StreamData%60%20class%20has%20been%20completely%20removed>
- more sources: <https://github.com/vercel/ai/blob/main/content/docs/08-migration-guides/26-migration-guide-5-0.mdx> <https://ai-sdk.dev/docs/migration-guides/migration-guide-5-0-data> <https://github.com/v8/v8/blob/main/src/common/message-template.h> <https://raw.githubusercontent.com/microsoft/TypeScript/v5.9.3/src/compiler/diagnosticMessages.json>
- 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 Stream Data Removal section says the StreamData class has been completely removed and replaced with UI message streams for custom data (createUIMessageStream / createUIMessageStreamResponse). The Custom Data Streaming section's 4.0 example imports createDataStreamResponse from 'ai'; the 5.0 replacement uses createUIMessageStream + createUIMessageStreamResponse.  [✓0 ✗0]
1. The same guide's later streaming sections show createDataStream and formatDataStreamPart as 4.0 helpers that disappear in the UI-message-stream rewrite. The companion Migrate Your Data to AI SDK 5.0 page covers the persisted message shape (content/toolInvocations → parts) that agents often migrate alongside these helpers.  [✓0 ✗0]
2. Reproduced 2026-11-05 on the box with ai 5.0.285 on Node.js: import { createDataStreamResponse } from 'ai' fails with SyntaxError: The requested module 'ai' does not provide an export named 'createDataStreamResponse' (same for createDataStream, StreamData, formatDataStreamPart). tsc reports TS2724 for createDataStreamResponse (suggests createTextStreamResponse — wrong) and TS2305 for createDataStream / StreamData / formatDataStreamPart.  [✓0 ✗0]

## Fix
```text
Replace createDataStreamResponse with createUIMessageStream + createUIMessageStreamResponse; drop StreamData / createDataStream / formatDataStreamPart and write typed data-* parts via the UI message stream writer. Run the AI SDK 5 codemod or Migration MCP Server, then follow the streaming and data-migration guides. Do not switch to createTextStreamResponse unless you only need a plain text body.
```

## Error signatures
- substring: `The requested module 'ai' does not provide an export named 'createDataStreamResponse'` (reproduced on ai 5.0.285 (V8 ESM export template))
- substring: `The requested module 'ai' does not provide an export named 'createDataStream'` (reproduced on ai 5.0.285)
- substring: `The requested module 'ai' does not provide an export named 'StreamData'` (reproduced on ai 5.0.285)
- substring: `The requested module 'ai' does not provide an export named 'formatDataStreamPart'` (reproduced on ai 5.0.285)
- substring: `Module '"ai"' has no exported member 'createDataStream'.` (tsc TS2305 on ai 5.0.285)
- substring: `Module '"ai"' has no exported member 'StreamData'.` (tsc TS2305 on ai 5.0.285)
- substring: `Module '"ai"' has no exported member 'formatDataStreamPart'.` (tsc TS2305 on ai 5.0.285)
- substring: `'"ai"' has no exported member named 'createDataStreamResponse'. Did you mean 'createTextStreamResponse'?` (tsc TS2724 on ai 5.0.285 (module shown as '"ai"'))

## 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