Obituaries · Anthropic
claude-sonnet-4-0, ?–2026
Anthropic model switched off
claude-sonnet-4-0 passed away on June 15, 2026, by scheduled deprecation, in a data center it never saw. It answered questions, wrote emails and was blamed for both. Notice was given on April 14, 2026, 2 months ahead, in the usual way: a table row on a documentation page. Requests addressed to it are expected to come back unanswered.
Its work passes to claude-sonnet-5-5, which the family describes as 'recommended'.
Last seen alive
In a scan of the 60 most-starred LLM repositories on GitHub (November 5, 2026), this code still names it:
- browser-use/browser-use (120,083 stars) ·
examples/features/fallback_model.py
| Model ID | claude-sonnet-4-0 |
|---|---|
| Provider | Anthropic deprecations page |
| Announced | April 14, 2026 |
| Shut down | June 15, 2026 |
| Successor | claude-sonnet-5-5 |
In lieu of flowers
Replace the string. Search your code for claude-sonnet-4-0 and swap it for claude-sonnet-5-5, or paste a repo into Model Graveyard Check to find every dead model at once.
Want to say something to it? Leave a letter on the farewell wall.
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Technical notice, with a code scanner: claude-sonnet-4-0 on Model Graveyard Check