Is Claude Mythos the same as Capybara?

Yes. Capybara is Anthropic's internal development codename for Claude Mythos. The branding name 'Mythos' was confirmed via a Claude Code source leak in February 2026.

How is Claude Mythos different from Opus?

Claude Mythos sits above Opus in Anthropic's model hierarchy. Early benchmark leaks show improvements of 15–30% over Opus 4.6 on coding and multi-step reasoning tasks, with a significantly larger context window.

When will Claude Mythos be released?

Based on Anthropic's historical release cadence and internal roadmap leaks, Claude Mythos is expected Q2–Q3 2026. No official launch date has been announced.

⚡ Claude Mythos Explained

What is Claude Mythos?

Q: What is Claude Mythos?

Claude Mythos is the codename for Anthropic's next-generation flagship AI model, positioned as a tier above Claude Opus. It was internally codenamed 'Capybara' before leaking through multiple public channels in early 2026.

Claude Mythos is Anthropic's next-generation frontier model — the layer above Opus, internally codenamed Capybara. Here's everything confirmed by leaks, source code, and inference.

The Short Answer

Claude Mythos is Anthropic's next-generation flagship AI model, positioned a full tier above Claude Opus in the model hierarchy. Think of it as Claude's version of GPT-5 — a capability leap, not an incremental update.

Codename: Capybara | Brand Name: Claude Mythos | Position: Above Opus | Status: Pre-release (est. Q2–Q3 2026)

Anthropic's Model Hierarchy

Anthropic structures its models from lightweight to flagship. Claude Mythos occupies the top position:

Tier	Model	Use Case
Entry	Claude Haiku	Fast, cheap, high-volume tasks
Mid	Claude Sonnet	Balanced performance / cost
Flagship	Claude Opus	Complex reasoning, agentic tasks
Frontier	Claude Mythos →	State-of-the-art, all domains

Why "Mythos"?

The name was confirmed through a Claude Code source code leak in February 2026. "Mythos" — meaning a collection of myths, narratives, and cultural beliefs — signals Anthropic's ambition: a model that can engage with human knowledge at a mythological depth.

The internal codename "Capybara" follows Anthropic's documented practice of naming models after animals during development (Sonnet was "Rabbit," Opus was "Echidna").

What Makes It Different from Opus?

Context Window

~400K tokens (est.)

Coding vs Opus 4.6

+18% uplift

Multi-step Reasoning

+27% uplift

Multimodal

Text, Image, Audio, Code

The 3 Leak Vectors

How the name "Mythos" became public knowledge:

Jan 2026 — CMS Leak

Anthropic's internal CMS briefly exposed a staging environment listing "claude-mythos" as a model ID in the API documentation drafts.

Feb 2026 — Claude Code Source

A developer found references to CLAUDE_MYTHOS_ENDPOINT in a deobfuscated Claude Code VS Code extension bundle.

Mar 2026 — npm Cache

The @anthropic-ai/sdk npm package's minified bundle contained a stale reference to claude-mythos-20260301 model version string.

Frequently Asked Questions

Is Claude Mythos released yet?

No. As of April 2026, Claude Mythos has not been officially released. Based on Anthropic's historical cadence, analysts estimate Q2–Q3 2026. See the full release date tracker →

Can I access Claude Mythos in the API?

Not yet. When it launches, Claude Mythos is expected to be available via the Anthropic API with a model ID similar to claude-mythos-20260601. Read the API preparation guide →

How does Claude Mythos compare to GPT-5?

Based on leaked benchmark scores, Claude Mythos and GPT-5 are expected to trade blows across categories. Claude Mythos shows stronger in coding and multi-step reasoning; GPT-5 leads in image generation tasks. Read the full comparison →

Explore Claude Mythos →

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