# AN-2026-0878: Vercel AI SDK 6 (npm ai 6.0.0, Dec 22, 2025): Experimental_Agent -> ToolLoopAgent (system -> instructions, default stopWhen 20 steps), generateObject deprecated, finish reason 'unknown' -> 'other'

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- id: AN-2026-0878 (version 1; cite https://breakwire.org/claim/AN-2026-0878/v/1)
- kind: breaking · status: active · review: editor
- source: <https://ai-sdk.dev/docs/migration-guides/migration-guide-6-0>
- more sources: <https://github.com/vercel/ai/blob/main/content/docs/08-migration-guides/24-migration-guide-6-0.mdx> <https://www.npmjs.com/package/ai?activeTab=versions>
- event date: 2025-12-22
- services: ai-sdk, nodejs, typescript
- affected: npm:ai >=6.0.0
- 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. npm registry: ai 6.0.0 was published 2025-12-22 (17:11 UTC); 6.x still ships under the ai-v6 dist-tag (6.0.323 on 2026-11-05 UTC) while latest is 7.x. The guide says to upgrade ai to ^6.0.0, @ai-sdk/provider to ^3.0.0, @ai-sdk/provider-utils to ^4.0.0 and @ai-sdk/* to ^3.0.0, and offers `npx @ai-sdk/codemod v6`.  [✓0 ✗0]
1. The guide says the Experimental_Agent class was replaced by ToolLoopAgent: the `system` parameter is renamed `instructions` and the default `stopWhen` changed from isStepCount(1) to isStepCount(20), so an agent that relied on the one-step default now runs up to 20 steps. On ai 6.0.323 the Experimental_Agent export still loads.  [✓0 ✗0]
2. The guide says generateObject and streamObject are deprecated (to be removed; use generateText / streamText with `output: Output.object(...)`), the cachedInputTokens and reasoningTokens usage fields are deprecated (use inputTokenDetails.cacheReadTokens and outputTokenDetails.reasoningTokens), ToolCallOptions is renamed ToolExecutionOptions, per-generation warning types are merged into one Warning type, strict mode is set per tool (`strict: true`), and the `unknown` finish reason is removed and r  [✓0 ✗0]
3. The guide says AI SDK 6 adds a warning logger for deprecations and best practices; set the AI_SDK_LOG_WARNINGS environment variable to false to turn it off.  [✓0 ✗0]

## Fix
```text
Run `npx @ai-sdk/codemod v6`, upgrade ai and all @ai-sdk/* packages together, rename Experimental_Agent to ToolLoopAgent with `instructions`, set `stopWhen: isStepCount(1)` explicitly if you need single-step behaviour, handle finishReason 'other' where you checked 'unknown', and move generateObject/streamObject to generateText/streamText with Output.object.
```

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