Claude Fable 5.1

Claude Fable 5.1 improves on Claude Fable 5 across the board, with the biggest gains in agentic coding, long-running agentic workflows, and knowledge work: long code refactors, front-end and visual code generation, and finance and analysis tasks in particular. It also tends to be more concise than Fable 5 in its plans and summaries. We recommend testing it as a direct upgrade wherever you use Fable 5 today, and alongside Opus 5 on reasoning-heavy tasks.

ChatAnthropic1M tokens$10.9006 / $54.503 · 1M

anthropic/claude-fable-5.1

Context
1M tokens
Completion cap
128,000
Tools
Yes
JSON
Yes
Released
2026-09-01

Call it from Geek Hub

Same OpenAI SDK. Change the base URL and the model id.

curl https://api.geekhub.mx/v1/chat/completions \
  -H "Authorization: Bearer $GEEKHUB_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-fable-5.1",
    "messages": [{"role": "user", "content": "Hola"}]
  }'
Get an API key

Frequently asked questions

What is Claude Fable 5.1?
Claude Fable 5.1 improves on Claude Fable 5 across the board, with the biggest gains in agentic coding, long-running agentic workflows, and knowledge work: long code refactors, front-end and visual code generation, and finance and analysis tasks in particular. It also tends to be more concise than Fable 5 in its plans and summaries. We recommend testing it as a direct upgrade wherever you use Fable 5 today, and alongside Opus 5 on reasoning-heavy tasks. Claude Fable 5.1 runs on the Geek Hub API (OpenAI-compatible). Model id: anthropic/claude-fable-5.1.
Is Claude Fable 5.1 free?
No. Input is $10.9006 per 1M tokens and output is $54.503 per 1M tokens on Geek Hub (markup included).
What is the context length of Claude Fable 5.1?
Claude Fable 5.1 has a 1M tokens context window. It supports up to 128,000 completion tokens.
Does Claude Fable 5.1 support tool calling and structured outputs?
Claude Fable 5.1 accepts tools and tool_choice for function calling. It also supports structured outputs via a JSON schema in response_format.
When was Claude Fable 5.1 released?
Claude Fable 5.1 was released on 2026-09-01.

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