Z.ai: GLM 5.1 vs GPT-5.1-Codex
Compare Z.ai: GLM 5.1 by Z-ai against GPT-5.1-Codex by OpenAI, context windows of 203K vs 400K, tested across 51 shared challenges.
Our Verdict
GPT-5.1-Codex
Z.ai: GLM 5.1Runner-up
No community votes yet. On paper, GPT-5.1-Codex has the edge — bigger model tier, bigger context window, major provider backing.
Too close to call
API pricing
Cost per 1M tokens
Z.ai: GLM 5.1
Input
$1.40
Output
$4.40
2.3× cheaper
GPT-5.1-Codex
Input
$1.25
1.1× cheaper
Output
$10.00
GPT-5.1-Codex wins input (1.1× cheaper)·Z.ai: GLM 5.1 wins output (2.3× cheaper)
Writing DNA
Style Comparison
Similarity
37%
GPT-5.1-Codex uses 3.6x more transitions
Z.ai: GLM 5.1
GPT-5.1-Codex
54%Vocabulary70%
18wSentence Length17w
0.31Hedging0.39
3.6Bold3.4
2.6Lists3.5
0.00Emoji0.00
0.43Headings0.50
0.11Transitions0.38
Based on 27 + 14 text responses
Research
What we learned reading every model
FAQ
