benchlm.ai

GPT-5.3 Codex vs Kimi K2.5 (Reasoning)

Side-by-side benchmark comparison across knowledge, coding, math, and reasoning.

Quick Verdict

GPT-5.3 Codex wins overall with a score of 85 vs 71 (14 point difference).GPT-5.3 Codex wins 4 out of 4 categories.

GPT-5.3 Codex

CreatorOpenAI
TypeProprietary
Context400K
Score85

Kimi K2.5 (Reasoning)

CreatorMoonshot AI
TypeOpen Weight
Context128K
Score71

Knowledge

GPT-5.3 Codex

GPT-5.3 Codex

96

Kimi K2.5 (Reasoning)

89

99
MMLU
92
97
GPQA
90
95
SuperGPQA
88
93
OpenBookQA
86

Coding

GPT-5.3 Codex

GPT-5.3 Codex

95

Kimi K2.5 (Reasoning)

84

95
HumanEval
84

Mathematics

GPT-5.3 Codex

GPT-5.3 Codex

97.1

Kimi K2.5 (Reasoning)

93

99
AIME 2023
94
99
AIME 2024
96
98
AIME 2025
95
95
HMMT Feb 2023
90
97
HMMT Feb 2024
92
96
HMMT Feb 2025
91
96
BRUMO 2025
93

Reasoning

GPT-5.3 Codex

GPT-5.3 Codex

94

Kimi K2.5 (Reasoning)

87

95
SimpleQA
88
93
MuSR
86

Frequently Asked Questions

Which is better, GPT-5.3 Codex or Kimi K2.5 (Reasoning)?

GPT-5.3 Codex scores higher overall with 85 vs 71, a difference of 14 points across all benchmarks.

Which is better for knowledge tasks, GPT-5.3 Codex or Kimi K2.5 (Reasoning)?

GPT-5.3 Codex leads in knowledge tasks with an average score of 96 vs 89.

Which is better for coding, GPT-5.3 Codex or Kimi K2.5 (Reasoning)?

GPT-5.3 Codex leads in coding with an average score of 95 vs 84.

Which is better for math, GPT-5.3 Codex or Kimi K2.5 (Reasoning)?

GPT-5.3 Codex leads in math with an average score of 97.1 vs 93.

Which is better for reasoning, GPT-5.3 Codex or Kimi K2.5 (Reasoning)?

GPT-5.3 Codex leads in reasoning with an average score of 94 vs 87.

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GPT-5.3 Codex vs GPT-5.4GPT-5.3 Codex vs Gemini 3.1 ProGPT-5.3 Codex vs Claude Opus 4.6GPT-5.3 Codex vs Grok 4.1GPT-5.3 Codex vs GPT-5.2GPT-5.3 Codex vs GPT-5.2-Codex