Anthropic Claude: Claude Mythos 5 API
Claude Mythos Preview is the preview channel of Anthropic's Mythos line, aimed at the hardest reasoning and long-horizon agentic work. It sits in the same top capability tier as the Fable series, with thinking always on and depth controlled through `output_config.effort`. As a preview channel its availability, quota and behaviour can change at any time, so it is not recommended on production-critical paths.
- Context window: 1,000,000 tokens
- Max output: 128,000 tokens
- Input: text, image, file
- Output: text
- Reasoning: Supported
- Tool calling: Supported
- File input: Supported
- Released: 2026-06-02
- Knowledge cutoff: 2025-12-01
Frequently Asked Questions
What is the context window of Claude Mythos 5?
Claude Mythos 5 supports a context window of up to 1,000,000 tokens.
Does Claude Mythos 5 support function calling?
Yes. Claude Mythos 5 supports tool / function calling.
Does Claude Mythos 5 support reasoning?
Yes. Claude Mythos 5 is a reasoning-capable model.
What is the knowledge cutoff of Claude Mythos 5?
The knowledge cutoff of Claude Mythos 5 is 2025-12-01.