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GPT-5.1 Codex vs Kimi K2 0905

Comparing GPT-5.1 Codex and Kimi K2 0905 across benchmarks, pricing, and capabilities.

OpenAI · Moonshot AI · Updated for 2026

Which is better?

GPT-5.1 Codex and Kimi K2 0905 trade strengths across price, capabilities, and technical limits. The better choice depends on the workload.

On price, Kimi K2 0905 is roughly 3.2x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

GPT-5.1 Codex also accepts a larger context window (400,000 input tokens), making it the stronger choice for long documents and large codebases.

Based on current benchmark, pricing, and model metadata for 2026.

Choose GPT-5.1 Codex

  • you process long inputs — it offers a 400,000 token context window
  • you want the most recent training data — it shipped Nov 2025

Choose Kimi K2 0905

  • cost matters — it's about 3.2x cheaper per token

At a glance

The differences that matter most.

GPT-5.1 Codex
OpenAI
Kimi K2 0905
Moonshot AI
Benchmark wins
—
—
Input price
$1.25 / M
$0.60 / M
Output price
$10.00 / M
$2.50 / M
Context window
400,000
262,144
Released
Nov 2025
Sep 2025
License
Proprietary
Proprietary

Performance Benchmarks

Comparative analysis across standard metrics

No common benchmarks found

GPT-5.1 Codex and Kimi K2 0905don't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Arena Performance

Playground indexes and blind preference scores

Pricing Analysis

Price comparison per million tokens

Kimi K2 0905 costs less

For input processing, GPT-5.1 Codex ($1.25/1M tokens) is 2.1x more expensive than Kimi K2 0905 ($0.60/1M tokens).

For output processing, GPT-5.1 Codex ($10.00/1M tokens) is 4.0x more expensive than Kimi K2 0905 ($2.50/1M tokens).

In conclusion, GPT-5.1 Codex is more expensive than Kimi K2 0905.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Mon Aug 24 2026 • llm-stats.com
OpenAI
GPT-5.1 Codex
Input tokens$1.25
Output tokens$10.00
Best providerOpenAI
Moonshot AI
Kimi K2 0905
Input tokens$0.60
Output tokens$2.50
Best providerNovita
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

GPT-5.1 Codex accepts 400,000 input tokens compared to Kimi K2 0905's 262,144 tokens. Kimi K2 0905 can generate longer responses up to 262,144 tokens, while GPT-5.1 Codex is limited to 128,000 tokens.

OpenAI
GPT-5.1 Codex
Input400,000 tokens
Output128,000 tokens
Moonshot AI
Kimi K2 0905
Input262,144 tokens
Output262,144 tokens
Mon Aug 24 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

GPT-5.1 Codex supports multimodal inputs, whereas Kimi K2 0905 does not.

GPT-5.1 Codex can handle both text and other forms of data like images, making it suitable for multimodal applications.

GPT-5.1 Codex

Text
Images
Audio
Video

Kimi K2 0905

Text
Images
Audio
Video

License

Usage and distribution terms

Both models are licensed under proprietary licenses.

Both models have usage restrictions defined by their respective organizations.

GPT-5.1 Codex

Proprietary

Closed source

Kimi K2 0905

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5.1 Codex was released on 2025-11-19, while Kimi K2 0905 was released on 2025-09-05.

GPT-5.1 Codex is 3 months newer than Kimi K2 0905.

GPT-5.1 Codex

Nov 19, 2025

9 months ago

2mo newer
Kimi K2 0905

Sep 5, 2025

11 months ago

Knowledge Cutoff

When training data ends

GPT-5.1 Codex has a documented knowledge cutoff of 2024-09-30, while Kimi K2 0905's cutoff date is not specified.

We can confirm GPT-5.1 Codex's training data extends to 2024-09-30, but cannot make a direct comparison without Kimi K2 0905's cutoff date.

GPT-5.1 Codex

Sep 2024

Kimi K2 0905

—

Provider Availability

GPT-5.1 Codex is available from OpenAI. Kimi K2 0905 is available from Novita.

GPT-5.1 Codex

openai logo
OpenAI
Input Price:Input: $1.25/1MOutput Price:Output: $10.00/1M

Kimi K2 0905

novita logo
Novita
Input Price:Input: $0.60/1MOutput Price:Output: $2.50/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against GPT-5.1 Codex and Kimi K2 0905 side-by-side, then vote on the output you prefer.

GPT-5.1 Codex
✓ Preferred
Kimi K2 0905
Open in Playground

FAQ

Common questions about GPT-5.1 Codex vs Kimi K2 0905.

Which is better, GPT-5.1 Codex or Kimi K2 0905?

GPT-5.1 Codex (OpenAI) and Kimi K2 0905 (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-5.1 Codex compare to Kimi K2 0905 in benchmarks?

GPT-5.1 Codex scores SWE-Bench Verified: 73.7%, SWE-Lancer: 66.3%, Terminal-Bench 2.0: 52.8%. Kimi K2 0905 scores HumanEval: 94.5%, MMLU: 90.2%, MATH: 89.1%, MMLU-Pro: 82.5%, GPQA: 75.8%.

Is GPT-5.1 Codex cheaper than Kimi K2 0905?

Kimi K2 0905 is 2.1x cheaper for input tokens. GPT-5.1 Codex costs $1.25/M input and $10.00/M output via openai. Kimi K2 0905 costs $0.60/M input and $2.50/M output via novita.

What are the context window sizes for GPT-5.1 Codex and Kimi K2 0905?

GPT-5.1 Codex supports 400K tokens and Kimi K2 0905 supports 262K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between GPT-5.1 Codex and Kimi K2 0905?

Key differences include context window (400K vs 262K), input pricing ($1.25 vs $0.60/M), multimodal support (yes vs no). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-5.1 Codex and Kimi K2 0905?

GPT-5.1 Codex is developed by OpenAI and Kimi K2 0905 is developed by Moonshot AI.

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