Model retirement dates / Anthropic
claude-sonnet-4-5-20250929
Anthropic will retire claude-sonnet-4-5-20250929 on 30 November 2026. After that date, API calls to it fail. The recommended replacement is claude-sonnet-5-5.
| Provider | Anthropic |
|---|---|
| Status | Retiring (as of 11 Nov 2026) |
| Shutdown | 30 November 2026 |
| Replacement | claude-sonnet-5-5 |
| Model type | Text |
| Announced | 30 September 2026 |
| Source | Anthropic deprecations page |
Before you switch
A replacement model answers the same prompt differently: tone, length, format, and whether JSON still parses. Driftline Pro runs your real prompts on claude-sonnet-4-5-20250929 and claude-sonnet-5-5 side by side in CI and shows what changed. See a drift test.
Check your code for it
Run this in your repository. No install and no API key; it lists every OpenAI, Anthropic and Google model ID it finds, with its retirement date and replacement:
npx -y @aidriftline/driftline .Or look for this ID only: grep -rn "claude-sonnet-4-5-20250929" . (misses aliases, Bedrock and Vertex names, and IDs split across lines).
To be warned automatically before the next retirement, add the free Driftline GitHub Action. It annotates the exact line in pull requests and can fail the build on retired models.
Checked against Anthropic's official page on 11 November 2026. Something wrong? hello@aidriftline.com