Anthropic
Claude Sonnet 4.5 (claude-sonnet-4-5-20250929) retires
23 days left — Nov 30, 2026
- What stops working
- API calls to claude-sonnet-4-5-20250929 stop being served. Also: temperature, top_p and top_k were removed in API version 2026-10-21 and return a 400 error on that version.
- Who is affected
- Any application pinned to the Sonnet 4.5 model string, and any integration that sets sampling parameters and upgrades its API version.
- Official migration path
- Move to claude-sonnet-5-5; omit sampling parameters and steer with prompting.
- What the official path does not cover
- Model behavior differs between versions; prompts and evals need re-running, not just a string swap.
- Source
- Anthropic model deprecations page · announced 2026-09-30 · verified 2026-11-07
Need this done before Nov 30, 2026?
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