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Anthropic: claude-fable-5.1
claude-fable-5.1
1M context128K outReasoningToolsVisionFilesCacheStructuredComputer useNative JSON
Released Sep 1, 2026Knowledge cutoff Nov 2025Updated Sep 2, 2026
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.
Mode chatTokenizer ClaudeReasoning levels maxModerated
Pricing
Input price
$7.20/ 1M tokens$10.0028% off
Output price
$36.00/ 1M tokens$50.0028% off
Compatible endpoints openai, anthropicVendor Anthropic
Uptime
Performance
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Supported parameters
All providers = every upstream serving this model supports it. Some providers = depends on which upstream handles the request. Default = the value sent when you leave the parameter unset.
| Parameter | Providers | Default |
|---|---|---|
| include_reasoning | All providers | - |
| max_completion_tokens | Some providers | - |
| max_tokens | All providers | - |
| reasoning | All providers | - |
| reasoning_effort | All providers | - |
| response_format | All providers | - |
| stop | All providers | - |
| structured_outputs | All providers | - |
| tools | All providers | - |
| verbosity | All providers | - |