The seven-day overage-included usage limit label has changed from "Fable 5 limit" to "Fable limit." New model aliases fable-5-1 and mythos-5-1, mapping to claude-fable-5-1 and claude-mythos-5-1, have been added to the model alias table alongside fable-5 and mythos-5.
Names in the bundlefable-5-1mythos-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 claude-on-vertex-ai touched a line naming mythos-5-1 after this was published.
| Claude Mythos 5.1 ([limited availability](https://anthropic.com/glasswing)) | `claude-mythos-5-1` |build-with-claude/claude-on-vertex-ai see the edit
Confirmed since
Anthropic's documentation has since written up 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
Added since
A small documentation edit on whats-new-fable-5-1 touched a line naming fable-5-1 after this was published.
To keep thinking valid across a long session, treat the conversation as append-only. Add instructions with a [mid-conversation system message](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages) ([turn-s…models/fable-5-1/whats-new-fable-5-1 see the edit
Confirmed since
Anthropic's documentation has since written up 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 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