Claude Sonnet 4.5
Balanced Claude model for coding, analysis, agent workflows, and cost control
ECI STANDING#61 of 266
SCORE146.84145.46–148.5 CI
FRONTIER LAGLaunched 5.5 months behindScores about what o3 did in April 2025.
SCORES LIKE THESE MODELSQwen3.5 397B-A17BAlibaba · Feb 2026146.96o3OpenAI · Apr 2025146.91
Full Epoch Capabilities Index ranking ↗Qwen 3.5 Plus (hosted 397B-A17B)Alibaba · Feb 2026146.73
MiniMax-M2.5MiniMax · Feb 2026146.51
From the lab
Launch announcement · Sep 29, 2025Released Claude Sonnet 4.5RELEASE DATESep 29, 2025
WEIGHTSClosed weights
CONTEXT WINDOW200K
MAX OUTPUT64K
REASONINGYes
TOOL CALLINGYes
INPUTStext, image, pdf
OUTPUTStext
Specifications from Models.dev. Availability and limits may differ by provider. Benchmark scores come from Epoch AI under CC BY 4.0.