GPT-5.5 vs Kimi K2-Thinking-0905
GPT-5.5 significantly outperforms across most benchmarks. Kimi K2-Thinking-0905 is 13.2x cheaper per token.
OpenAI · Moonshot AI · Updated for 2026
Which is better?
GPT-5.5 outperforms in 3 benchmarks (BrowseComp, GPQA, Humanity's Last Exam), while Kimi K2-Thinking-0905 is better at 0 benchmarks. GPT-5.5 significantly outperforms across most benchmarks.
On price, Kimi K2-Thinking-0905 is roughly 13.2x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
GPT-5.5 also accepts a larger context window (1,050,000 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-5.5
- you want the strongest raw capability — it leads on 3 of 3 shared benchmarks
- you process long inputs — it offers a 1,050,000 token context window
- you want the most recent training data — it shipped Apr 2026
Choose Kimi K2-Thinking-0905
- cost matters — it's about 13.2x cheaper per token
- you need open weights you can self-host or fine-tune
At a glance
The differences that matter most.
Performance Benchmarks
Comparative analysis across standard metrics
GPT-5.5 outperforms in 3 benchmarks (BrowseComp, GPQA, Humanity's Last Exam), while Kimi K2-Thinking-0905 is better at 0 benchmarks.
GPT-5.5 significantly outperforms across most benchmarks.
Arena Performance
Playground indexes and blind preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, GPT-5.5 ($5.00/1M tokens) is 10.6x more expensive than Kimi K2-Thinking-0905 ($0.47/1M tokens).
For output processing, GPT-5.5 ($30.00/1M tokens) is 15.0x more expensive than Kimi K2-Thinking-0905 ($2.00/1M tokens).
In conclusion, GPT-5.5 is more expensive than Kimi K2-Thinking-0905.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
GPT-5.5 accepts 1,050,000 input tokens compared to Kimi K2-Thinking-0905's 262,144 tokens. Kimi K2-Thinking-0905 can generate longer responses up to 262,144 tokens, while GPT-5.5 is limited to 128,000 tokens.
Input Capabilities
Supported data types and modalities
GPT-5.5 supports multimodal inputs, whereas Kimi K2-Thinking-0905 does not.
GPT-5.5 can handle both text and other forms of data like images, making it suitable for multimodal applications.
GPT-5.5
Kimi K2-Thinking-0905
License
Usage and distribution terms
GPT-5.5 is licensed under a proprietary license, while Kimi K2-Thinking-0905 uses MIT.
License differences may affect how you can use these models in commercial or open-source projects.
Proprietary
Closed source
MIT
Open weights
Release Timeline
When each model was launched
GPT-5.5 was released on 2026-04-23, while Kimi K2-Thinking-0905 was released on 2025-09-05.
GPT-5.5 is 8 months newer than Kimi K2-Thinking-0905.
Apr 23, 2026
4 months ago
7mo newerSep 5, 2025
11 months ago
Knowledge Cutoff
When training data ends
GPT-5.5 has a documented knowledge cutoff of 2025-12-01, while Kimi K2-Thinking-0905's cutoff date is not specified.
We can confirm GPT-5.5's training data extends to 2025-12-01, but cannot make a direct comparison without Kimi K2-Thinking-0905's cutoff date.
Dec 2025
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Provider Availability
GPT-5.5 is available from OpenAI. Kimi K2-Thinking-0905 is available from DeepInfra, Novita, Fireworks.
GPT-5.5
Kimi K2-Thinking-0905
Outputs Comparison
Judge for yourself.
Run your own prompts against GPT-5.5 and Kimi K2-Thinking-0905 side-by-side, then vote on the output you prefer.
FAQ
Common questions about GPT-5.5 vs Kimi K2-Thinking-0905.