Claude Sonnet 4.5 vs Claude Opus 4

Compare Claude Sonnet 4.5 and Claude Opus 4, both from Anthropic, context windows of 200K vs 200K, tested across 29 shared challenges. Updated April 2026.

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

Claude Sonnet 4.5 and Claude Opus 4 are both competitive models. Claude Sonnet 4.5 costs $3/M input tokens vs $15/M for Claude Opus 4. Context windows: 200K vs 200K tokens. Compare their real outputs side by side below.

Key Differences Between Claude Sonnet 4.5 and Claude Opus 4

Claude Sonnet 4.5 is made by anthropic while Claude Opus 4 is from anthropic. Claude Sonnet 4.5 has a 200K token context window compared to Claude Opus 4's 200K. On pricing, Claude Sonnet 4.5 costs $3/M input tokens vs $15/M for Claude Opus 4.

Our Verdict
Claude Sonnet 4.5
Claude Sonnet 4.5
Claude Opus 4
Claude Opus 4

No community votes yet. On paper, these are closely matched - try both with your actual task to see which fits your workflow.

Claude Sonnet 4.5 is 5.0x cheaper per token — worth considering if cost matters.

Too close to call
Writing DNA

Style Comparison

Similarity
100%

Claude Sonnet 4.5 uses 4.0x more emoji

Claude Sonnet 4.5
Claude Opus 4
64%Vocabulary64%
94wSentence Length62w
0.48Hedging0.52
4.9Bold4.4
8.0Lists9.1
0.45Emoji0.11
1.91Headings1.87
0.07Transitions0.27
Based on 20 + 16 text responses
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Claude Sonnet 4.5Claude Opus 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
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