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Claude Sonnet 4.5

Anthropic, 29 Sep 2025.

Lab

Anthropic

Released

29 Sep 2025

Kind

Language, Language modeling/generation

Training compute

Not disclosed

Parameters

Not disclosed

Capability index

146.8 (Epoch)

Organisations

Anthropic

Country

United States

See it in the 3D sky Paper or announcement

Data: Epoch AI (Creative Commons Attribution), releases too new for it from OpenRouter, and METR. Updated 25 Sep 2026.