Claude Mythos Preview
Claude Mythos Preview is Anthropic’s published frontier research model, documented in an April 2026 system card and deployed to selected Project Glasswing partners. The general-purpose model demonstrated substantial coding and vulnerability-research capabilities, motivating a restricted defensive-security program rather than general release. It is included as a substantive published research checkpoint, distinct from the later Fable/Mythos 5 family. Partner APIs existed, but no general public inference or open weights were offered.
2026-04-07
Unreleased
Undisclosed proprietary architecture
Proprietary
Specifications
- Parameters
- Unreleased
- Architecture
- Undisclosed proprietary architecture
- License
- Proprietary
- Type
- text
- Modalities
- text
Benchmark Scores
Advanced Specifications
- Model Family
- Claude
- API Access
- Not Available
- Chat Interface
- Not Available
Capabilities & Limitations
- Capabilities
- agentic codingvulnerability analysissecurity researchtool-assisted reasoning
- Known Limitations
- Restricted Project Glasswing deployment; not generally available.Anthropic describes the checkpoint as unreleased for general use and deprecated its partner identity June 9, 2026.Published evaluations do not establish unrestricted production availability.
- Notable Use Cases
- defensive security researchcritical-software reviewfrontier-model evaluation