Anthropic
claude-sonnet-4-5-20250929 model retirement
Stops workingSubscribe to AnthropicShare
On November 30, 2026, the model claude-sonnet-4-5-20250929 will be retired. Anthropic deprecated the model on September 30, 2026. Any calls using model claude-sonnet-4-5-20250929 after November 30, 2026 will fail.
The error you get from November 30, 2026
What Anthropic answers a call to claude-sonnet-4-5-20250929 once the model is gone, as recorded from real responses:
{"type":"error","error":{"type":"not_found_error","message":"model: claude-sonnet-4-5-20250929"}}What to use instead of claude-sonnet-4-5-20250929
Move to claude-sonnet-5-5, as recommended by Anthropic.
In Anthropic's words
API model name: claude-sonnet-4-5-20250929; Current state: Deprecated; Deprecated: September 30, 2026; Tentative retirement date: November 30, 2026
Facts
- API
- Anthropic
api.anthropic.com - Model
claude-sonnet-4-5-20250929- Released
- September 29, 2025 (models.dev)
- Kind
- Model retirement
- Announced
- September 30, 2026
- Takes effect
- November 30, 2026
- Calls after that day
- Fail
- Source
- Deprecations page
- Last updated
- Verified
- , against Anthropic's own pages
Questions
When does claude-sonnet-4-5-20250929 shut down?
Calls to the model claude-sonnet-4-5-20250929 on Anthropic stop working on November 30, 2026.
What happens to calls after November 30, 2026?
They fail from that day.
What error does claude-sonnet-4-5-20250929 return once it is shut down?
Anthropic answers HTTP 404: "model: claude-sonnet-4-5-20250929". Send another model to fix it.
When was claude-sonnet-4-5-20250929 released?
claude-sonnet-4-5-20250929 was released on September 29, 2025, according to models.dev.
How do I find the calls this hits in my code?
Okapi reads your repository, finds the calls this change hits and opens a pull request with the fix. It never commits to your branches: every change comes as a pull request you review.
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Is your code calling this?
Okapi finds the calls this change hits in your repo and opens the pull request with the fix before November 30, 2026.