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TechAnthropic releases Claude Fable 5.1 and Mythos 5.1 with 1M token context
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Anthropic has released Claude Fable 5.1 and Mythos 5.1 via its API, according to official documentation. The new models feature a 1 million token context window with 128K maximum output, improved capabilities for agentic coding, research, document handling, spreadsheets, and slides, as well as better computer use and long-horizon tasks. Adaptive thinking with adjustable effort is included. Pricing is set at $10 per million input tokens and $50 per million output tokens, with cached input tokens at $0.25 per million—representing a 75% reduction in cache read costs compared to Fable 5. Fable 5.1 is available to all API customers, while Mythos 5.1 is currently limited to participants in Project Glasswing.
Source report
Anthropic has announced the availability of Claude Fable 5.1 and Mythos 5.1 in its API, according to official documentation. The update represents a significant upgrade for long-running agentic workloads.
Key Features
- 1 million token context window with 128K maximum output
- Enhanced performance in agentic coding, research, document processing, spreadsheets, and slides
- Improved computer use and long-horizon task execution
- Adaptive thinking with adjustable effort levels
Pricing
| Metric | Cost | |--------|------| | Input tokens | $10 per million tokens | | Output tokens | $50 per million tokens | | Cached input tokens | $0.25 per million tokens |
Cache reads are 75% cheaper compared to Fable 5.
Availability
- Fable 5.1 is available to all API customers
- Mythos 5.1 is currently limited to Project Glasswing participants
Source
ai_for_successNeutral / independent
Part of this Story
Anthropic releases Claude Fable 5.1 with 75% cheaper cache reads, cutting costs up to 45%