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AnthropicClaude Mythos 5.1

External Link

Claude Mythos 5.1 is the invitation-only Project Glasswing version of Claude Fable 5.1 for approved cybersecurity and life-sciences work.

Context
1,000,000 tokens
Inputs
Text, Image
Outputs
Text
Released
Sep 1, 2026

Providers & Pricing

0 sourced offerings

No Directly Sourced Provider Price YetAPI pricing is provider-specific and stays unknown until a serving provider publishes an exact offering for this model version.

At a Glance

Model Facts

Identity

Status
active
Developer ID
claude-mythos-5-1
Released
Sep 1, 2026
Version
Claude Mythos 5.1
License
Unknown

Capacity

Context
1,000,000 tokens
Maximum output
128,000 tokens
Total parameters
Unknown
Active parameters
Unknown
Knowledge cutoff
Jun 1, 2026

Interface and Access

Inputs
Text, Image
Outputs
Text
API available
Yes
Open weights
No
Self-hostable
No
Reasoning
Yes
Vision
Yes
Tool calling
Yes
Capabilities
chat, generation, reasoning, tools

This page represents one immutable developer model ID. Serving endpoints, pricing, regions, quantizations, and service tiers attach separately and never create duplicate model records.

Version Lineage

PredecessorUnknown
SuccessorsUnknown
Aliasesclaude-mythos-5-1

Explicit Unknowns

  • Architecture
  • Tokenizer
  • Provider pricing

Primary Evidence

Sources and Observation Date

Claude Mythos 5.1 | Claude Platform DocsAnthropic · observed Sep 2, 2026Claude Mythos 5.1 | Claude Platform DocsAnthropic · observed Sep 2, 2026Claude Fable 5.1 and Mythos 5.1Anthropic · observed Sep 2, 2026

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Questions

Claude Mythos 5.1 FAQs

What is Claude Mythos 5.1?+

Claude Mythos 5.1 is the invitation-only Project Glasswing version of Claude Fable 5.1 for approved cybersecurity and life-sciences work. It is developed by Anthropic and its current sourced lifecycle status is active.

What inputs and outputs does Claude Mythos 5.1 support?+

Claude Mythos 5.1's current record lists Text and Image as input and Text as output.

How much context does Claude Mythos 5.1 support?+

The current record lists a 1,000,000-token context window and a maximum output of 128,000 tokens.

Is Claude Mythos 5.1 available through an API?+

Claude Mythos 5.1 is marked as API-available. No directly sourced serving-provider record is attached yet.

How much does Claude Mythos 5.1 cost through an API?+

No directly sourced token price is currently attached to Claude Mythos 5.1. Missing prices remain unknown rather than being inferred from another model or provider.

What capabilities and tasks does Claude Mythos 5.1 support?+

Claude Mythos 5.1's recorded capabilities are chat, generation, reasoning, and tools. Its supported tasks are image and text.

Can Claude Mythos 5.1 be self-hosted?+

Claude Mythos 5.1 is not marked as an open-weight model. Self-hosting is marked as unsupported, with no license recorded.

Does Claude Mythos 5.1 have related versions or aliases?+

No predecessor is recorded. No successor is recorded. Recorded aliases are claude-mythos-5-1.

Which models can Claude Mythos 5.1 be compared with?+

The current compatible peer set includes Claude Fable 5, Claude Opus 5, Claude Sonnet 5, GPT-5.6 Sol, and Gemini 3.1 Pro. Compatibility requires shared sourced modalities and tasks; it does not imply that one model is better. Browse model comparisons →

How current is the Model Markets record for Claude Mythos 5.1?+

Claude Mythos 5.1 was last verified Sep 2, 2026 from Anthropic's primary source, “Claude Mythos 5.1 | Claude Platform Docs.” The evidence is classified as official fact.

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