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Claude Sonnet 4.5 vs Mistral Medium 3.5

2 vs 1 benchmarks won

Anthropic
Claude Sonnet 4.5
Mistral
Mistral Medium 3.5
Overview
CompanyAnthropicMistral
Release dateSep 29 2025Apr 29 2026
Model type
Open sourceNoYes
Specifications
Parameters
128B
Context window
256k
Benchmarks
Science reasoning
GPQA Diamond
83.4%
Software engineering
SWE-Bench Verified
77.2%
77.6%
Multimodal understanding
MMMU
68%
Timeline
Release gapClaude Sonnet 4.5 shipped 212 days before Mistral Medium 3.5

Which is better: Claude Sonnet 4.5 or Mistral Medium 3.5?

Claude Sonnet 4.5 leads Mistral Medium 3.5 on 2 of the tracked benchmarks (GPQA Diamond, SWE-Bench Verified, MMMU). Claude Sonnet 4.5 shipped 212 days before Mistral Medium 3.5, so benchmark comparisons should account for the intervening progress.

Mistral Medium 3.5 is an open-source / open-weight model; Claude Sonnet 4.5 is proprietary.

On SWE-Bench Verified, Mistral Medium 3.5 scores 77.6%, 0.4 points above Claude Sonnet 4.5 at 77.2%.

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 Medium 3.5 released?
Mistral Medium 3.5 was released by Mistral on Apr 29 2026.
Which is better at coding, Claude Sonnet 4.5 or Mistral Medium 3.5?
On SWE-Bench Verified (real-world software-engineering tasks), Mistral Medium 3.5 leads — Claude Sonnet 4.5 scores 77.2% and Mistral Medium 3.5 scores 77.6%.
Is Claude Sonnet 4.5 or Mistral Medium 3.5 open source?
Mistral Medium 3.5 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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