Anthropic
Anthropic Claude model for long-running agentic coding and knowledge work.
1M ctxUSD 4 / 1M input tok; USD 20 / 1M output tok
Introducing Claude Fable 5.1AnthropicReleased September 1, 2026
Claude Fable 5.1
The ultimate model for demanding reasoning and long-horizon agentic work, featuring 0.025x cache reads ($0.25/MTok).
reasoning-llmProprietary API$10.00 / 1M tok (0.025x Cache Reads)Context: 1M (1,000,000 tokens)Arena ELO: 1565
Technical Specifications
Architecture Type
Long-Horizon Multistep Agentic Transformer
Total Parameters
Frontier Agent Scale
Context Window
1M (1,000,000 tokens)
Max Output Tokens
128K (128,000 tokens)
Knowledge Cutoff
June 2026
Supported Modalities
text, code, vision, reasoning
License & Access
Anthropic Commercial Terms
Benchmark Evaluations
Math500
99.4
Mmlu Pro
93.1
Gpqa Diamond
88
Swe Bench Verified
87.5
Chatbot Arena ELO
1565
Deep Architectural Overview
Claude Fable 5.1 extends Claude Fable 5 with cache reads at a quarter of prior cost ($0.25/MTok) and superior capabilities on multi-hour agentic coding, deep research, and finished document synthesis. Always-on adaptive thinking handles the most intractable problems.
Strengths & Considerations
Core Strengths
- Industry-leading 0.025x cache read multiplier ($0.25 per 1M tokens)
- 87.5% SWE-bench Verified coding rating
- Always-on adaptive thinking with turn-scoped system prompts
- 1,000,000 token context window and 128k output buffer
Known Limitations
- Forced tool use returns an error; requires natural adaptive tool invocation
Token & API Pricing
Input Tokens (1M)$10.00
Output Tokens (1M)$50.00
Cached Input (1M)$0.2500
Batch API Discount50% Off Standard
Pricing is verified directly against Anthropic's developer documentation and API rate sheets.
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