Claude Fable 5
Overview
Claude Fable 5 is Anthropic’s Mythos-class frontier model, built for autonomous knowledge work and coding. With adaptive thinking always on, it excels at long-running, complex, asynchronous end-to-end tasks—problems that are extended, ambiguous, or involve many interdependent steps. It accepts text and image inputs and offers a 1M-token context window.
Key Features
- Frontier Capability: Anthropic’s strongest tier, for the most challenging knowledge work
- Adaptive Thinking: Always-on adaptive reasoning that scales thinking depth to task difficulty
- Long Context: 1M-token context, suited to long-running complex tasks
Best Use Cases
- Autonomous Coding: End-to-end, multi-step, self-verifying complex coding tasks
- Deep Knowledge Work: Research, synthesis, and long-document reasoning
- Asynchronous Long Tasks: Extended work that once required frequent human oversight
Specifications
| Item | Detail |
|---|---|
| Platform model ID | claude-fable-5 |
| Context window | 1,000,000 tokens |
| Input modalities | Text, image |
| Reasoning / thinking | Supported (adaptive thinking always on) |
| First released (market) | 2026-06-09 |
| Live pricing | See the model marketplace |
Capabilities and Limitations
| Capability | Description |
|---|---|
| Reasoning | Extremely strong. Frontier-level complex reasoning and autonomous coding |
| Multimodal | Supports text and image input |
| Context Window | 1,000,000 tokens |
| Speed | Slower. Always-on deep thinking trades speed for quality |
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