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Claude Sonnet 4.5

Anthropic

Released
September 2025
Data date
September 8, 2026
Speed
43.8 tokens/s
Output throughput
Price
Input · Output / 1M tokens
Input
Text, Image
Output
Text

Claude Sonnet 4.5 stood out for computer use. Anthropic highlighted its 61.4% result on OSWorld-Verified in the launch announcement. As the predecessor to Claude Sonnet 4.6, it targeted complex coding and agent tasks.

Specifications and access

SpecificationValue and source
Weights
ProprietarySource
Access
Context window
200,000 tokensSource
Knowledge cutoff
January 2025Source
Notes
Anthropic does not disclose parameter countsSource
API model ID
claude-sonnet-4-5-20250929Source
Source status
active (legacy)Source
Release
2025-09-29Source
Maximum output
64,000 tokensSource
Input
Text, imagesSource
Output
TextSource
Reasoning mode
extended thinkingSource
Knowledge cutoff
2025-01 reliable / 2025-07 trainingSource
Tool calling
Structured output