Model · Anthropic · Text
Claude Mythos 5
Anthropic's restricted frontier model — the same underlying model as Claude Fable 5 with safeguards lifted in select domains. Invitation-only through Project Glasswing; superseded by Claude Mythos 5.1 (2026-09-01).
- Modality
- Text
- License
- Proprietary (Proprietary)
- Context window
- 1,000,000 tokens 1M default with up to 128k output. Uses the tokenizer introduced with Opus 4.7 — the same text produces roughly 30% more tokens than pre-4.7 Claude models.
- Released
- June 9, 2026
- Last verified
- September 8, 2026
- Runs locally
- No
- Also handles
- vision
Strengths
- State-of-the-art at cybersecurity, biology research, and healthcare workloads
- Same underlying model as Claude Fable 5, without Fable's safeguard routing in approved domains
- 1M-token context with up to 128k output
Weaknesses
- Not generally available — invitation-only via Project Glasswing, no self-serve sign-up
- Same premium pricing as Fable 5 ($10/$50 per MTok)
- Closed weights — cannot be self-hosted
Try it
| Where | Type | Notes |
|---|---|---|
| Anthropic (Project Glasswing) | hosted-api | Approved customers only, via Anthropic, AWS, or Google Cloud account teams |
Version history
- Claude Haiku 5.5 Oct 2026
- Claude Sonnet 5.5 Sep 2026
- Claude Opus 5.5 Sep 2026
- Claude Fable 5.1 Sep 2026
- Claude Mythos 5.1 Sep 2026
Official sources
- Claude Mythos vendor
- Model docs docs
- Announcement announcement
Change log
- — Deprecated — superseded by Claude Mythos 5.1 (released 2026-09-01). Still in limited availability; not listed on Anthropic's deprecation table.
- — Initial entry. Released 2026-06-09 in limited availability via Project Glasswing, succeeding Claude Mythos Preview.
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