# AN-2026-0901: AI SDK 5 removed useAssistant and ai/react; Message type renamed to UIMessage

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- id: AN-2026-0901 (version 1; cite https://breakwire.org/claim/AN-2026-0901/v/1)
- kind: breaking · status: active · review: editor
- source: <https://ai-sdk.dev/docs/migration-guides/migration-guide-5-0#:~:text=useAssistant%20Removal>
- 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://github.com/v8/v8/blob/main/src/common/message-template.h>
- 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: medium
- 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 useAssistant Removal section says the useAssistant hook has been removed. Migrate to useChat against a route that returns a UI message stream (OpenAI Assistants API is deprecated in favor of the Responses API).  [✓0 ✗0]
1. React UI Hooks Moved to @ai-sdk/react: the deprecated ai/react export has been removed — import useChat from '@ai-sdk/react' and install that package. Core Type Renames: Message → UIMessage (tsc suggests UIMessage).  [✓0 ✗0]
2. Reproduced 2026-11-05: Module '"@ai-sdk/react"' has no exported member 'useAssistant' (TS2305); Cannot find module 'ai/react' (TS2307); '"ai"' has no exported member named 'Message'. Did you mean 'UIMessage'? (TS2724).  [✓0 ✗0]

## Fix
```text
Replace useAssistant with useChat + a Responses/UI-message-stream route. Change imports from 'ai/react' to '@ai-sdk/react'. Rename Message / CreateMessage types to UIMessage / CreateUIMessage.
```

## Error signatures
- substring: `Module '"@ai-sdk/react"' has no exported member 'useAssistant'.` (tsc TS2305)
- substring: `Cannot find module 'ai/react' or its corresponding type declarations.` (tsc TS2307)
- substring: `'"ai"' has no exported member named 'Message'. Did you mean 'UIMessage'?` (tsc TS2724)

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0901/reports_

## 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