Use Claude text editor with Claude Fable 5.1

by AnthropicCode

Claude Fable 5.1 uses Claude text editor through Opper on the Messages endpoint, passed through as Anthropic defines it.

UseClaude text editorwithin

Add Claude text editor to Claude Fable 5.1

Set up with agents

Paste this into your coding agent (Claude Code, Cursor, Codex, and more) and it will set up and build with Opper for you.

Get your API key

In your code

1curl https://api.opper.ai/v3/compat/v1/messages \
2  -H "Authorization: Bearer $OPPER_API_KEY" \
3  -H "Content-Type: application/json" \
4  -d '{"model": "anthropic/claude-fable-5-1", "max_tokens": 1024,
5       "messages": [{"role": "user", "content": "List the files in this repo."}],
6       "tools": [{"type": "text_editor_20250728", "name": "str_replace_based_edit_tool"}]}'

Where you can run it

Claude Fable 5.1 runs Claude text editor on the routes below.

Provider	Region	Zero data retention	Training	Input	Output	Cache read
Anthropic	US		No	$10.00	$50.00	$0.25$12.50 write
Google Cloud	Multi		No	$10.00	$50.00	$0.25$12.50 write

The model

Claude Fable 5.1

by Anthropic

Claude Fable 5.1 is Anthropic's frontier model for agentic coding, knowledge work, and long-running problem solving, with a 1M token context and 128K output.