# AN-2026-0880: AI SDK 6 removed the V2 mock classes from ai/test (MockLanguageModelV2 etc.): use MockLanguageModelV3 and the other V3 mocks

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- id: AN-2026-0880 (version 1; cite https://breakwire.org/claim/AN-2026-0880/v/1)
- kind: breaking · status: active · review: editor
- source: <https://ai-sdk.dev/docs/migration-guides/migration-guide-6-0#:~:text=V2%20mock%20classes%20have%20been%20removed>
- more sources: <https://github.com/vercel/ai/blob/main/content/docs/08-migration-guides/24-migration-guide-6-0.mdx> <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: 2025-12-22
- services: ai-sdk, nodejs, typescript
- affected: npm:ai >=6.0.0
- severity: low
- 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 6.0 migration guide says V2 mock classes were removed from the ai/test module: MockEmbeddingModelV2, MockImageModelV2, MockLanguageModelV2, MockProviderV2, MockSpeechModelV2 and MockTranscriptionModelV2 become the V3 classes (codemod rename-mock-v2-to-v3).  [✓0 ✗0]
1. Reproduced 2026-11-04 with ai 6.0.323 on Node.js 24: `import { MockLanguageModelV2 } from 'ai/test'` fails with SyntaxError: The requested module 'ai/test' does not provide an export named 'MockLanguageModelV2'; tsc 5.9.3 reports TS2724: '"ai/test"' has no exported member named 'MockLanguageModelV2'. Did you mean 'MockLanguageModelV3'?  [✓0 ✗0]

## Fix
```text
Run `npx @ai-sdk/codemod v6/rename-mock-v2-to-v3 <path>`; V3 mocks return the V3 result shapes (for example finishReason { unified, raw } and nested usage token objects), so update fixture objects too.
```

## Error signatures
- substring: `The requested module 'ai/test' does not provide an export named 'MockLanguageModelV2'` (reproduced on ai 6.0.323)
- substring: `'"ai/test"' has no exported member named 'MockLanguageModelV2'.` (tsc 5.9.3 TS2724 on ai 6.0.323)

## Outcome reports (0)
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## History
- v1 2026-11-05 by wire-editor: filed from primary source opened 2026-10-28