GPT-5.1 Codex vs Kimi K2 Thinking
Side-by-side benchmark comparison across coding, math, reasoning, speed, and pricing.
GPT-5.1 Codex by OpenAI wins on 4 of 7 benchmarks against Kimi K2 Thinking by Vertex, which leads on 3. This head-to-head comparison covers coding, math, reasoning, speed, and pricing metrics from our benchmark data.
Category-by-Category Breakdown
Coding: In coding, GPT-5.1 Codex scores 1197 on Design Arena ELO compared to Kimi K2 Thinking's 1125, while GPT-5.1 Codex scores 1174 on Website Arena ELO compared to Kimi K2 Thinking's 1125.
Reasoning: In reasoning, Kimi K2 Thinking scores 83.4% on GPQA Diamond compared to GPT-5.1 Codex's 65.0%.
Context: In context, GPT-5.1 Codex scores 400K on Context Length compared to Kimi K2 Thinking's 262K.
Pricing Comparison
GPT-5.1 Codex costs $1.3/1M input tokens and $10.0/1M output tokens, while Kimi K2 Thinking costs $0.60/1M input and $2.5/1M output. Kimi K2 Thinking is the more affordable option for API usage.
Verdict
Kimi K2 Thinking leads across the board in affordability, making it the stronger overall choice in this comparison.
View Individual Model Pages
GPT-5.1 Codex vs Kimi K2 Thinking — FAQ
Which is better, GPT-5.1 Codex or Kimi K2 Thinking?
GPT-5.1 Codex wins on more benchmarks overall (4 vs 3). However, the best choice depends on your specific needs — each model excels in different areas.
How does GPT-5.1 Codex compare to Kimi K2 Thinking for coding?
SWE-bench Verified data is not available for both models. Check the detailed comparison charts above for other coding-related metrics.
Is GPT-5.1 Codex cheaper than Kimi K2 Thinking?
Yes, Kimi K2 Thinking is cheaper. GPT-5.1 Codex costs $1.3/1M input and $10.0/1M output tokens. Kimi K2 Thinking costs $0.60/1M input and $2.5/1M output tokens.
Which is faster, GPT-5.1 Codex or Kimi K2 Thinking?
Output speed data is not available for both models. Check the speed section of the comparison above for available performance data.
What benchmarks does the GPT-5.1 Codex vs Kimi K2 Thinking comparison cover?
This comparison covers 7 benchmarks including GPQA Diamond, Input Cost, Output Cost, Context Length, Cached Input Cost, Design Arena ELO, Website Arena ELO. Metrics span general intelligence, coding, math, reasoning, speed, and cost categories.