Overview
Claude Mythos 5 is the limited-access counterpart to Claude Fable 5, released June 9, 2026. It is the same underlying model as Fable 5 with the same capability set, but deployed with its safeguards lifted in some areas rather than the full classifiers that gate the generally available version. Because of that, Mythos 5 is not generally available: it is offered in limited availability to approved customers through Project Glasswing, and is the direct successor to Claude Mythos Preview.
Access is initially granted to a small group of vetted cyberdefenders and infrastructure providers, with Anthropic planning a trusted access program for biology to accelerate biomedical research — customers work through their Anthropic, AWS, or Google Cloud account team to be approved. Teams without Glasswing access are directed to Fable 5, the generally available Mythos-class model. Mythos 5 carries the same 1M-token context window, 128k max output tokens, and $10/$50 per-million-token pricing as Fable 5, and shares its adaptive-thinking behavior. Anthropic's alignment assessment reports Mythos 5's misalignment behavior as "similar to Opus 4.8," and it is designated a Covered Model with 30-day data retention.
What's New
Frontier Cybersecurity Capability
Anthropic describes Mythos 5 as having the strongest cybersecurity capabilities of any model in the world. The Glasswing access model exists precisely because lifting safeguards in some areas exposes capability that Anthropic gates behind vetting — Mythos 5 is positioned for sanctioned defensive security research and infrastructure hardening by approved organizations, not open deployment.
~10× Faster Drug Design
In molecular design work, Mythos 5 accelerated protein design workflows by roughly 10× and generated 9 of 14 strong drug candidates in an evaluated set — moving the model from research curiosity toward a practical accelerant for biomedical discovery pipelines run by approved labs.
Autonomous Genomics Research
Mythos 5 conducted autonomous single-cell analysis across 138 species. In one result, a custom machine-learning model it produced outperformed a published model from a Science paper while being roughly 100× smaller — a concrete demonstration of frontier-level scientific reasoning applied end to end rather than as a chat assistant.
Novel Hypothesis Generation
For early-stage research, scientists preferred Mythos 5's novel hypotheses roughly 80% of the time over Opus-class models — reinforcing its positioning as a research collaborator for the hardest discovery work rather than a general-purpose assistant.
Performance & Positioning
| Dimension | Claude Mythos 5 |
|---|---|
| Underlying model | Same as Fable 5, with safeguards lifted in some areas |
| Cybersecurity | "Strongest of any model in the world" (Anthropic) |
| Protein / drug design | ~10× faster; 9 of 14 strong candidates |
| Genomics | Autonomous single-cell analysis across 138 species |
| Hypothesis generation | Preferred ~80% of the time vs. Opus-class |
| Availability | Limited availability via Project Glasswing only |
| Alignment | Misalignment "similar to Opus 4.8" (Anthropic assessment) |
Because Mythos 5 and Fable 5 are the same model under the hood, raw capability benchmarks track Fable 5 (frontier-leading FrontierCode score, and stronger long-context memory use than Opus 4.8 in Slay the Spire testing). The distinction is governance, not performance: Mythos 5 trades general availability for safeguards lifted in some areas under a vetted-access program.
Migration Guide
The supported upgrade path is from Claude Mythos Preview to Mythos 5; Anthropic publishes step-by-step migration instructions for existing Glasswing customers. Key points when moving over:
- Same integration model as Fable 5. Adaptive thinking is always on (no
disabledmode), the raw chain of thought is never returned, and you control depth with theeffortparameter. - Access is the gate, not the API. Mythos 5 uses the
claude-mythos-5identifier, but availability is controlled through Project Glasswing approval — contact your Anthropic, AWS, or Google Cloud account team. - Covered Model retention. Mythos 5 carries 30-day data retention and is not available under zero data retention; confirm this fits your compliance posture before migrating sensitive workloads.
Pricing & Plans
| Plan | Price |
|---|---|
| API – Input | $10 per million tokens |
| API – Output | $50 per million tokens |
| Access | Project Glasswing limited availability — approval required |
| Cloud availability | Through Anthropic, AWS, or Google Cloud account teams |
| Alternative | Claude Fable 5 — the generally available Mythos-class model |
Access note: Pricing matches Fable 5, but Mythos 5 cannot be purchased on demand. It is provisioned only to approved Project Glasswing customers. If you need Mythos-class capability without the approval process, Fable 5 delivers the same underlying model with safety classifiers in place.
Best For
- Approved cybersecurity research teams conducting sanctioned defensive security and infrastructure-hardening work
- Infrastructure providers vetted into Project Glasswing for capability that is gated from open deployment
- Selected biomedical and genomics labs — protein design, single-cell analysis, hypothesis generation — if approved under Anthropic's planned trusted biology access program
- Organizations with an Anthropic, AWS, or Google Cloud account team that can sponsor Glasswing approval
- Existing Claude Mythos Preview customers upgrading to the production Mythos 5 model
Everyone else should use Claude Fable 5, which delivers the same underlying model with safety classifiers and full general availability.
FAQ
What is Claude Mythos 5?
Claude Mythos 5 is Anthropic's June 9, 2026 limited-access frontier model — the same underlying model as Claude Fable 5 but with its safeguards lifted in some areas. It is the successor to Claude Mythos Preview and is offered only in limited availability through Project Glasswing — initially to approved cyberdefenders and infrastructure providers, with a trusted biology access program planned.
How is Mythos 5 different from Claude Fable 5?
They are the same model under the hood. Fable 5 is generally available with full safety classifiers and is what nearly all teams should use. Mythos 5 has its safeguards lifted in some areas and is restricted to vetted Project Glasswing customers. The difference is governance and access, not raw capability.
How do I get access to Claude Mythos 5?
Mythos 5 is not generally available. Access is granted to approved customers through Project Glasswing; you request it through your Anthropic, AWS, or Google Cloud account team. Customers without access use Claude Fable 5, the generally available Mythos-class model.
How much does Claude Mythos 5 cost?
Pricing matches Fable 5 at $10 per million input tokens and $50 per million output tokens. However, Mythos 5 cannot be purchased on demand — it is provisioned only to approved Project Glasswing customers.
Is Mythos 5 a successor to Mythos Preview?
Yes. Anthropic publishes a dedicated migration guide for moving from Claude Mythos Preview to Mythos 5 for existing Glasswing customers. Mythos 5 uses the claude-mythos-5 API identifier.
