Claude Fable 5.1
Claude Fable 5.1 is an advanced AI model for demanding reasoning and long-horizon agentic work.
Recommended for
- Seed
- Series A
SSIE
Stage Fit Recommendations
Following data shows why Claude Fable 5.1 is recommended for listed teams. The Fit Score represents the percentage fit of Claude Fable 5.1 to each company stages, as calculated by the SSIE.
Stage
Fit Score
Fit Reasons
Seed
$10k–$100k MRR
79- Adaptive thinking mode with steerable depth via effort
- Turn-scoped system messages
- Readable progress updates between tool calls
Series A
$100k–$500k MRR
72- Data residency and regional hosting controls
- Active security and vulnerability disclosure programme
- Handles classifier refusals and retries on another Claude model
- Preserved thinking blocks across model switches and conversation changes
- Context window of 1 million tokens
- Max output of 128k tokens
Claude Fable 5.1 is an AI model designed for complex reasoning tasks and long-running agentic workflows. It offers a 128k token output limit and supports advanced features like cache reads at a quarter of the cost. The model has a base input pricing of $10 per million tokens and $50 per million tokens for output. It extends the capabilities of Claude Fable 5 with improved long-running agentic coding, multistep research, and document, spreadsheet, and slide work. For most workloads, users are recommended to start with Claude Opus 5. Claude Mythos 5.1 provides the same capabilities to Project Glasswing participants only. The model has specific pricing for cache writes and cache hits, with cache hits priced at 0.025x the base input cost.
Pricing
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