Model summary
Speed
Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) is amongst the leading models in intelligence, but particularly expensive when comparing to other models of similar price. The model supports text and image input, outputs text, and has a 1M tokens context window.
Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) scores 66 on the Artificial Analysis Intelligence Index, placing it well above average among comparable models (median: 36). When evaluating the Intelligence Index, it generated 140M tokens, which is very verbose in comparison to the median of 71M.
Pricing for Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) is $10.00 per 1M input tokens (expensive, median: $2.00) and $50.00 per 1M output tokens (expensive, median: $10.00). In total, it cost $8523.16 to evaluate Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) on the Intelligence Index.
| Reasoning | Yes This page shows the reasoning version of this model. A non-reasoning variant may also exist. |
|---|---|
| Input modality | Supports: text and image |
| Output modality | Supports: text |
| Context window | 1M ~1500 A4 pages of size 12 Arial font |
Metrics are compared against models of the same class:
- Non-reasoning models → compared only with other non-reasoning models
- Reasoning models → compared across both reasoning and non-reasoning
- Open weights models → compared only with other open weights models of the same size class:
- Tiny: ≤4B parameters
- Small: 4B–40B parameters
- Medium: 40B–150B parameters
- Large: >150B parameters
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Proprietary models → compared across proprietary and open weights models of the same price range, using a blended 3:1 input/output price ratio:
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<$0.15 per 1M tokens
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$0.15–$1 per 1M tokens
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$1 per 1M tokens Highlights
Speed
Intelligence #
Artificial Analysis Intelligence Index
Artificial Analysis Intelligence Index by Open Weights / Proprietary
Intelligence Evaluations
Agentic real-world work tasks, (Elo-500)/2000 Agentic tool use
Agentic coding & terminal use
Coding
Reasoning & knowledge
Scientific reasoning
Physics reasoning
Knowledge
1 - hallucination rate
Long context reasoning
Agentic knowledge work, Elo
Agentic SaaS workflows
Legal agentic work, criterion pass rate
Agentic business operations
Quantitative analysis on spreadsheets & documents
Instruction following
Long-horizon agentic tasks
Kubernetes incident root-cause analysis
Visual reasoning
AA-Briefcase
AA-Briefcase Elo
AA-Omniscience
AA-Omniscience Index
Intelligence Index Comparisons #
Intelligence Index vs. Cost per Intelligence Index Task
Token Use #
Output Tokens per Intelligence Index Task
Cost #
Cost per Intelligence Index Task
Cost to Run Artificial Analysis Intelligence Index
Pricing: Cache Hit, Input, and Output
Context Window #
Context Window
Frequently Asked Questions #
Common questions about Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback)
Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) was released on September 1, 2026.
Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) was created by Anthropic.
Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) scores 66 on the Artificial Analysis Intelligence Index, placing it well above average among other reasoning models in a similar price tier (median: 36).
Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) costs $10.00 per 1M input tokens (at the higher end, median: $2.00) and $50.00 per 1M output tokens (at the higher end, median: $10.00), based on Anthropic's API.
Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) costs $10.00 per 1M input tokens and $50.00 per 1M output tokens (based on Anthropic's API). For a blended rate (7:2:1 cache hit/input/output ratio), this is $7.17 per 1M tokens. Pricing may vary by provider. Compare provider pricing
When evaluated on the Intelligence Index, Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) generated 140M output tokens, which is at the higher end compared to other reasoning models in a similar price tier (median: 71M).
Yes, Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) is a reasoning model. It uses extended thinking or chain-of-thought reasoning to work through complex problems before providing an answer.
Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) supports text and image input.
Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) supports text output.
Yes, Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) supports image input and can analyze, describe, and answer questions about images.
Yes, Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) is multimodal. It can process text and image input and generate text output.
Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) has a context window of 1.0M tokens. This determines how much text and conversation history the model can process in a single request.
No, Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) is proprietary. The model weights are not publicly available.
Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) is a proprietary model and Anthropic has not disclosed the model size or parameter count.
Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) achieves a score of 66 on the Artificial Analysis Intelligence Index. This composite benchmark evaluates models across reasoning, knowledge, mathematics, and coding.
Yes, Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) is available via API through 1 provider. [Compare API providers](/models/claude-fable-5-1/providers)
Claude Fable 5.1 (Adaptive Reasoning, Max Effort, Default Fallback) is available through 1 API provider. [Compare providers](/models/claude-fable-5-1/providers)