Model Comparison

GPT-5 Codex vs Kimi K2 InstructWhich is better in 2026?

Comparing GPT-5 Codex and Kimi K2 Instruct across benchmarks, pricing, and capabilities.

Verdict: GPT-5 Codex vs Kimi K2 Instruct — which is better?

GPT-5 Codex (by OpenAI) and Kimi K2 Instruct (by Moonshot AI) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.

Choose GPT-5 Codex if…

  • you want the most recent training data — it shipped Sep 2025

Choose Kimi K2 Instruct if…

  • you need open weights you can self-host or fine-tune
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Performance Benchmarks

Comparative analysis across standard metrics

No common benchmarks found

GPT-5 Codex and Kimi K2 Instructdon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only Kimi K2 Instruct specifies input context (200,000 tokens). Only Kimi K2 Instruct specifies output context (200,000 tokens).

OpenAI
GPT-5 Codex
Input- tokens
Output- tokens
Moonshot AI
Kimi K2 Instruct
Input200,000 tokens
Output200,000 tokens
Sat Jun 13 2026 • llm-stats.com

License

Usage and distribution terms

GPT-5 Codex is licensed under a proprietary license, while Kimi K2 Instruct uses MIT.

License differences may affect how you can use these models in commercial or open-source projects.

GPT-5 Codex

Proprietary

Closed source

Kimi K2 Instruct

MIT

Open weights

Release Timeline

When each model was launched

GPT-5 Codex was released on 2025-09-15, while Kimi K2 Instruct was released on 2025-07-11.

GPT-5 Codex is 2 months newer than Kimi K2 Instruct.

GPT-5 Codex

Sep 15, 2025

9 months ago

2mo newer
Kimi K2 Instruct

Jul 11, 2025

11 months ago

Knowledge Cutoff

When training data ends

GPT-5 Codex has a documented knowledge cutoff of 2024-09-30, while Kimi K2 Instruct's cutoff date is not specified.

We can confirm GPT-5 Codex's training data extends to 2024-09-30, but cannot make a direct comparison without Kimi K2 Instruct's cutoff date.

GPT-5 Codex

Sep 2024

Kimi K2 Instruct

—

Outputs Comparison

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Key Takeaways

OpenAI

No standout differentiators in the data we have for this pair.

Moonshot AI
Larger context window (200,000 tokens)
Has open weights

Detailed Comparison

AI Model Comparison Table
Feature
OpenAI
GPT-5 Codex
Moonshot AI
Kimi K2 Instruct

FAQ

Common questions about GPT-5 Codex vs Kimi K2 Instruct.

Which is better, GPT-5 Codex or Kimi K2 Instruct?

GPT-5 Codex (OpenAI) and Kimi K2 Instruct (Moonshot AI) each have strengths in different areas. Compare their benchmark scores, pricing, context windows, and capabilities above to determine which fits your needs.

How does GPT-5 Codex compare to Kimi K2 Instruct in benchmarks?

GPT-5 Codex scores SWE-Bench Verified: 74.5%. Kimi K2 Instruct scores MATH-500: 97.4%, GSM8k: 97.3%, CBNSL: 95.6%, HumanEval: 93.3%, MMLU-Redux: 92.7%.

What are the context window sizes for GPT-5 Codex and Kimi K2 Instruct?

GPT-5 Codex supports an unknown number of tokens and Kimi K2 Instruct supports 200K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between GPT-5 Codex and Kimi K2 Instruct?

Key differences include licensing (Proprietary vs MIT). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-5 Codex and Kimi K2 Instruct?

GPT-5 Codex is developed by OpenAI and Kimi K2 Instruct is developed by Moonshot AI.

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