What
The table mapping short model names to full model ids was refreshed and now includes fable-5, mythos-5, opus-5 and opus-4-8 alongside the existing opus, sonnet and haiku entries. An alias being listed does not mean the model is available to your account.
Evidence
mythos-5
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
Names in the bundleopus-5fable-5mythos-5opus-4-8
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 prompting-claude-opus-4-8 touched a line naming opus-4-8 after this was published.
This guide covers the prompting patterns specific to Claude Opus 4.8. For the API changes involved in moving from Claude Opus 4.8 to Claude Opus 5.5, see [Migrating to Claude Opus 5.5 from Claude Opus 4.8](https://platform.claude.com/docs/…build-with-claude/prompt-engineering/prompting-claude-opus-4-8 see the edit
Added since
A small documentation edit on Models overview touched a line naming opus-5 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 mythos-5, 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 Or, for the model with the same capabilities and no access approval requirement: touched a line naming mythos-5 after this was published.
* If you replay conversation history on an earlier model, strip `thinking` and `redacted_thinking` blocks from prior assistant turns first. Thinking blocks from `claude-fable-5` and `claude-mythos-5` are readable only by the model that pro…models/fable-5/migration-guide see the edit
Added since
A small documentation edit on whats-new-fable-5-1 touched a line naming fable-5 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 opus-4-8, on Create Session.
- `"claude-opus-4-8"`api/beta/sessions/create see the edit
One source agreesOne thing we can check says the same as this entry.
Anthropic's documentation agrees
Anthropic's documentation has since written up opus-5, on Create Session.