Claude Sonnet 4.5 vs Z.ai: GLM 5.1

Compare Claude Sonnet 4.5 by Anthropic against Z.ai: GLM 5.1 by Z-ai, context windows of 200K vs 203K, tested across 41 shared challenges. Updated April 2026.

Which is better, Claude Sonnet 4.5 or Z.ai: GLM 5.1?

Claude Sonnet 4.5 and Z.ai: GLM 5.1 are both competitive models. Claude Sonnet 4.5 costs $3/M input tokens vs $1.4/M for Z.ai: GLM 5.1. Context windows: 200K vs 203K tokens. Compare their real outputs side by side below.

Key Differences Between Claude Sonnet 4.5 and Z.ai: GLM 5.1

Claude Sonnet 4.5 is made by anthropic while Z.ai: GLM 5.1 is from z-ai. Claude Sonnet 4.5 has a 200K token context window compared to Z.ai: GLM 5.1's 203K. On pricing, Claude Sonnet 4.5 costs $3/M input tokens vs $1.4/M for Z.ai: GLM 5.1.

Our Verdict
Claude Sonnet 4.5
Claude Sonnet 4.5
Z.ai: GLM 5.1
Z.ai: GLM 5.1

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

Z.ai: GLM 5.1 is 3.4x cheaper per token — worth considering if cost matters.

Too close to call
Writing DNA

Style Comparison

Similarity
98%

Claude Sonnet 4.5 uses 45.2x more emoji

Claude Sonnet 4.5
Z.ai: GLM 5.1
64%Vocabulary54%
94wSentence Length18w
0.48Hedging0.31
4.9Bold3.6
8.0Lists2.6
0.45Emoji0.00
1.91Headings0.43
0.07Transitions0.11
Based on 20 + 27 text responses
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Claude Sonnet 4.5Z.ai: GLM 5.1

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