Answer · Writing
What AI models does Claude use?
Claude runs on Claude Fable 5 (Anthropic), Claude Fable 5.1 (Anthropic), Claude Haiku 4.5 (Anthropic), Claude Mythos 5 (Anthropic), Claude Mythos 5.1 (Anthropic), Claude Opus 4.5 (Anthropic), Claude Opus 4.8 (Anthropic), Claude Opus 5 (Anthropic) and Claude Sonnet 5 (Anthropic), and routes requests between them.
- Models used
- 9
- Primary model
- Claude Fable 5
- Public API
- Yes
- Last checked
- 2026-09-12
Model claims are labelled by how we know them: Claude Fable 5 — disclosed, Claude Fable 5.1 — disclosed, Claude Haiku 4.5 — disclosed, Claude Mythos 5 — disclosed, Claude Mythos 5.1 — disclosed, Claude Opus 4.5 — disclosed, Claude Opus 4.8 — disclosed, Claude Opus 5 — disclosed and Claude Sonnet 5 — disclosed. "Disclosed" means the vendor says so in public; "inferred" means it was derived from documentation, headers or release notes.
Context window: 1000000.
Other stack signals: Python, TypeScript, Go, Java, Ruby, PHP, C#, AWS Bedrock, Google Cloud and Microsoft Foundry.
Cite this answer
Tomorrow. “What AI models does Claude use?” Tomorrow AI & Emerging Tech Index, AlienSquad, updated 2026-09-12. https://tomorrow.aliensquad.ai/q/what-models-does-claude-use
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