GPT-5.1 Codex vs Kimi K2.5
Side-by-side benchmark comparison across coding, math, reasoning, speed, and pricing.
Kimi K2.5 by Moonshot AI wins on 6 of 9 benchmarks against GPT-5.1 Codex by OpenAI, 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, Kimi K2.5 scores 1228 on Design Arena ELO compared to GPT-5.1 Codex's 1197, while Kimi K2.5 scores 1261 on Website Arena ELO compared to GPT-5.1 Codex's 1174.
Reasoning: In reasoning, Kimi K2.5 scores 84.9% 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 K2.5's 262K.
Pricing Comparison
GPT-5.1 Codex costs $1.3/1M input tokens and $10.0/1M output tokens, while Kimi K2.5 costs $0.45/1M input and $2.3/1M output. Kimi K2.5 is the more affordable option for API usage.
Speed Comparison
GPT-5.1 Codex generates output at 85 tok/s compared to Kimi K2.5's 45 tok/s, and the time to first token is 400 ms for GPT-5.1 Codex versus 1210 ms for Kimi K2.5. GPT-5.1 Codex delivers faster throughput.
Verdict
For developers prioritizing speed, GPT-5.1 Codex has the edge. For those who value affordability, Kimi K2.5 is the stronger choice.
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GPT-5.1 Codex vs Kimi K2.5 — FAQ
Which is better, GPT-5.1 Codex or Kimi K2.5?
Kimi K2.5 wins on more benchmarks overall (6 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 K2.5 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 K2.5?
Yes, Kimi K2.5 is cheaper. GPT-5.1 Codex costs $1.3/1M input and $10.0/1M output tokens. Kimi K2.5 costs $0.45/1M input and $2.3/1M output tokens.
Which is faster, GPT-5.1 Codex or Kimi K2.5?
GPT-5.1 Codex is faster, generating output at 85 tok/s compared to 45 tok/s. Faster output speed means shorter wait times for API responses.
What benchmarks does the GPT-5.1 Codex vs Kimi K2.5 comparison cover?
This comparison covers 9 benchmarks including GPQA Diamond, Output Speed, Time to First Token, Input Cost, Output Cost, Context Length, Cached Input Cost, Design Arena ELO, and more. Metrics span general intelligence, coding, math, reasoning, speed, and cost categories.