LLM
Preview
Proprietary
Claude Mythos 5.1
Vetted cybersecurity and life-sciences research
Release2026-09-01
Context1M
Max output128,000 tokens
ParametersUndisclosed
Local / VRAMAPI only
LicenseProprietary
Overview
Claude Mythos 5.1 is a model in the LLM category from Anthropic. It was released in 2026-09-01. The vendor is based in US. Best for: Vetted cybersecurity and life-sciences research.
Notes: Identical to Claude Fable 5.1 apart from safeguards; successor to Mythos 5. Not retired before 2027-09-01.
Strengths
- Same model as Fable 5.1 with more permissive cyber and life-sciences safeguards
- 1M context, 128K output
- Powers Claude Security
Limits
- Invite-only via trusted access programs
- 30-day data retention; no zero data retention unless authorized
- High price
Specifications
| Vendor | Anthropic |
|---|---|
| Category | LLM |
| Release | 2026-09-01 |
| Status | Preview |
| License | Proprietary |
| Commercial use | Not specified |
| Context window | 1M |
| Max output tokens | 128,000 |
| Input modalities | Text, Image |
| Output modalities | Text |
| Prompt types | Text |
| Negative prompts | No |
| Max outputs | 1 |
| Local deployment | No |
| API access | Yes |
| Pricing | $10 / $50 per 1M token (invite-only; cache reads $0.25) |
| Confidence | High |
| Vendor country | US |
| Vendor type | Frontier lab |
Pricing & hardware
$10 / $50 per 1M token (invite-only; cache reads $0.25)
API-only: local GPU memory is not applicable. API access is available.