'Fable 5' branding shortened to 'Fable' in usage-limit messages

Usage-limit text now says Fable limit, and fable-5-1 and mythos-5-1 aliases were added.

Read from

Names in the bundlefable-5-1mythos-5-1

What the documentation says

Documented inapi/about-claude/model-deprecations

Since it was published

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.

Confirmed since 15 Sep 2026 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 11 Sep 2026 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 10 Sep 2026 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

How sure we are

Two sources agreeTwo things we can check say the same as this entry.

Anthropic's documentation agreesAnthropic's documentation has since written up fable-5-1, on Create Session.

Anthropic's release notes agreeAdded 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

See this entry in the whole of v2.1.257 →