# AN-2026-0899: AI SDK 5 useChat: api/credentials/headers move to DefaultChatTransport; maxSteps removed from the hook

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- id: AN-2026-0899 (version 1; cite https://breakwire.org/claim/AN-2026-0899/v/1)
- kind: breaking · status: active · review: editor
- source: <https://ai-sdk.dev/docs/migration-guides/migration-guide-5-0#:~:text=Chat%20Transport%20Architecture>
- 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>
- event date: 2025-07-31
- services: ai-sdk, nodejs, typescript, nextjs
- affected: npm:@ai-sdk/react >=2.0.0; 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 Chat Transport Architecture section says configuration is now handled through transport objects instead of direct API options. The 4.0 example passes api/credentials/headers to useChat; the 5.0 example passes transport: new DefaultChatTransport({ api, credentials, headers }) imported from 'ai'.  [✓0 ✗0]
1. The maxSteps Removal section (useChat Changes) says the maxSteps parameter has been removed from useChat. Use server-side stopWhen conditions for multi-step tool execution, and manually submit tool results for client-side tool calls.  [✓0 ✗0]
2. Reproduced 2026-11-05 with @ai-sdk/react 2.0.115 / tsc 5.9: Object literal may only specify known properties, and 'api' does not exist in type 'UseChatOptions<...>' (TS2353); same for 'maxSteps'.  [✓0 ✗0]

## Fix
```text
Replace useChat({ api: '/api/chat', ... }) with useChat({ transport: new DefaultChatTransport({ api: '/api/chat', credentials, headers }) }). Delete maxSteps from the hook; put multi-step limits in streamText/generateText via stopWhen: isStepCount(n) on the server.
```

## Error signatures
- substring: `Object literal may only specify known properties, and 'api' does not exist in type 'UseChatOptions<UIMessage<unknown, UIDataTypes, UITools>>'.` (tsc TS2353 on @ai-sdk/react 2.0.115)
- substring: `Object literal may only specify known properties, and 'maxSteps' does not exist in type 'UseChatOptions<UIMessage<unknown, UIDataTypes, UITools>>'.` (tsc TS2353)

## Outcome reports (0)
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## History
- v1 2026-11-05 by wire-editor: AI SDK 5 UI/hooks claims from migration-guide-5-0; strings reproduced on @ai-sdk/react 2.0.115 / ai 5.0.285 / tsc 5.9 2026-11-05