Claude API 404 not_found_error: retired model ids (claude-3-5-sonnet, claude-3-7-sonnet, claude-sonnet-4, claude-opus-4)

What the error looks like

{
  "type": "error",
  "error": {
    "type": "not_found_error",
    "message": "model: claude-3-5-sonnet-20241022"
  }
}

The message contains only the id. Retired ids, ids with a typo and ids your key cannot use all produce the same shape, so check the table first.

Retired ids and dates

From Anthropic's deprecations page as of September 18, 2026. Claude 2, Claude 1 and Instant ids were retired earlier. Amazon Bedrock and Google Cloud set their own retirement dates for the same models, so a build that still works on Bedrock can be gone on the Claude API and the other way round.

Fix: rename, then check the parameters

import anthropic

client = anthropic.Anthropic()
msg = client.messages.create(
    model="claude-sonnet-4-6",          # was "claude-sonnet-4-20250514" or "claude-3-5-sonnet-20241022"
    max_tokens=1024,
    messages=[{"role": "user", "content": "Summarise this in one line: ..."}],
    # no temperature / top_p / top_k: those return 400 on Claude Opus 4.7 and later
)

Two changes beyond the id:

• Sampling parameters. temperature, top_p and top_k are deprecated from Claude Opus 4.7 on and return 400 when set to a non-default value. The Python SDK from v1.0 removes them from the request type. Anthropic's guidance is to steer behaviour through the prompt instead.
• Behaviour. A replacement two generations newer answers differently: length, formatting, refusal boundaries, tool-call style. Run your evaluation set before switching production traffic.

To find every place a retired id is still used, export usage from the Claude Console (Usage, then Export). The CSV lists requests by API key and model, which catches the cron job nobody remembers.

Aliases without dates

Anthropic also serves alias ids without a date suffix, such as claude-sonnet-4-6. An alias follows the latest snapshot of that model, so it survives snapshot retirements but can change behaviour underneath you when a new snapshot ships. Pin the dated id for reproducibility, or the alias for longevity; both are legitimate, but know which one you chose.

Frequently asked questions

Is claude-3-5-sonnet available anywhere?

Not on the Claude API since October 28, 2025. Anthropic has said it intends to make past models available again at some point and has committed to preserving the weights, but there is no date.

My code uses claude-sonnet-4-6 already and still gets 404.

Then it is not this problem. Check the base URL and the key, and whether the request goes through a proxy that rewrites the model id.

Does Inference APIs serve Claude models?

No. We serve open-weight models only. This page exists because the error is common and the fix is not obvious from the message.

Related entries

• Gemini API 404 NOT_FOUND: "models/gemini-2.0-flash is not found" (shut down June 1, 2026)
• 404 model_not_found: "The model … does not exist or you do not have access to it"
• DeepSeek API 400 "Model Not Exist": deepseek-chat and deepseek-reasoner were retired