Claude Opus 4.5 vs Claude Sonnet 4

Compare Claude Opus 4.5 and Claude Sonnet 4, both from Anthropic, tested across 34 shared challenges. Updated April 2026.

Which is better, Claude Opus 4.5 or Claude Sonnet 4?

Claude Opus 4.5 and Claude Sonnet 4 are both competitive models. Compare their real outputs side by side below.

Key Differences Between Claude Opus 4.5 and Claude Sonnet 4

Claude Opus 4.5 is made by anthropic while Claude Sonnet 4 is from anthropic.

Our Verdict
Claude Opus 4.5
Claude Opus 4.5
Claude Sonnet 4
Claude Sonnet 4Runner-up

No community votes yet. On paper, Claude Opus 4.5 has the edge — bigger model tier, newer.

Too close to call
Writing DNA

Style Comparison

Similarity
100%

Claude Sonnet 4 uses 6.3x more transitions

Claude Opus 4.5
Claude Sonnet 4
64%Vocabulary62%
55wSentence Length111w
0.86Hedging0.40
5.8Bold5.0
4.5Lists9.3
0.15Emoji0.88
1.59Headings2.16
0.05Transitions0.33
Based on 24 + 17 text responses
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Ask them anything yourself

Claude Opus 4.5Claude Sonnet 4

279 AI models invented the same fake scientist.

We read every word. 250 models. 2.14 million words. This is what we found.

AI Hallucination Index 2026
Free preview13 of 58 slides
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