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Claude Sonnet 4.5 vs Mistral Small 3.1

3 vs 0 benchmarks won

Anthropic
Claude Sonnet 4.5
Mistral
Mistral Small 3.1
Overview
CompanyAnthropicMistral
Release dateSep 29 2025Mar 17 2025
Model type
Open sourceNoYes
Specifications
Parameters
Context window
Benchmarks
Science reasoning
GPQA Diamond
83.4%
Software engineering
SWE-Bench Verified
77.2%
Multimodal understanding
MMMU
68%
Timeline
Release gapMistral Small 3.1 shipped 196 days before Claude Sonnet 4.5

Which is better: Claude Sonnet 4.5 or Mistral Small 3.1?

Claude Sonnet 4.5 leads Mistral Small 3.1 on 3 of the tracked benchmarks (GPQA Diamond, SWE-Bench Verified, MMMU). Mistral Small 3.1 shipped 196 days before Claude Sonnet 4.5, so benchmark comparisons should account for the intervening progress.

Mistral Small 3.1 is an open-source / open-weight model; Claude Sonnet 4.5 is proprietary.

Direct benchmark comparisons are unavailable — at least one of these models has not published scores on GPQA Diamond, SWE-Bench Verified, or MMMU.

Frequently asked questions

When was Claude Sonnet 4.5 released?
Claude Sonnet 4.5 was released by Anthropic on Sep 29 2025.
When was Mistral Small 3.1 released?
Mistral Small 3.1 was released by Mistral on Mar 17 2025.
Is Claude Sonnet 4.5 or Mistral Small 3.1 open source?
Mistral Small 3.1 is an open-source / open-weight model released by Mistral. Claude Sonnet 4.5 is a proprietary model released by Anthropic.

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