Nothing to try yet Notable
A claude-fable-5-1 model id is recognized and becomes the fable family default, with UI text updated to Fable 5.1.
A new claude-fable-5-1 model id is recognized, along with a matching claude-mythos-5-1 variant. The fable family's default, best, and latest_per_family selections now point to claude-fable-5-1, though a gateway-specific override still uses claude-fable-5. UI text changes from "Fable 5" to "Fable 5.1".
Names in the bundleclaude-fable-5-1claude-mythos-5-1
Documented inapi/about-claude/model-deprecations
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Added since
A small documentation edit on Models overview touched a line naming claude-fable-5-1 after this was published.
| [Claude Platform on AWS ID](https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws) | `claude-fable-5-1` | `claude-opus-5` | `claude-sonnet-5` | `claude-haiku-4-5` |models/overview see the edit
Confirmed since
Anthropic's documentation has since written up claude-mythos-5-1, on Messages.
- `"claude-fable-5-1" or "claude-mythos-5-1" or "claude-sonnet-5" or 14 more`api/beta/messages see the edit
Confirmed since
Anthropic's documentation has since written up claude-fable-5-1, on Create Session.
- `BetaManagedAgentsModel = "claude-fable-5-1" or "claude-sonnet-5" or "claude-fable-5" or 11 more or string`api/beta/sessions/create see the edit
Two sources agreeTwo things we can check say the same as this entry.
Anthropic's documentation agrees
Anthropic's documentation has since written up claude-fable-5-1, on Create Session.
Anthropic's release notes agree
Added Claude Fable 5.1 (claude-fable-5-1), now the default Fable model — 1M context, $10/$50 per Mtok with $0.25/Mtok cache reads