claude-mythos-preview: retirement date and replacement

This model is deprecated: it still works, but is no longer recommended and no retirement date has been announced. Anthropic gives at least 60 days' notice — migrating now avoids depending on that window.

These dates apply to Anthropic-operated platforms: the Claude API, Claude Platform on AWS and Microsoft Foundry. Amazon Bedrock and Google Cloud set their own retirement schedules — on those platforms, status and dates can differ.

What actually happens

A request naming a retired model returns an API error. The part that catches teams out in production: nothing switches automatically to an equivalent model, and the error surfaces at call time, not at deploy time. Model IDs pinned in an environment file or an old evaluation script are the ones that break most often, because nobody re-reads them.

Check your own code

Search your code, environment variables and config files for the exact ID:

grep -rn "claude-mythos-preview" . --exclude-dir=node_modules

Source: Anthropic's official documentation — read on 8/3/2026, 5:54:33 PM UTC. See all models →