When was Kimi K2 (0905) released?

Kimi K2 (0905) was released by Moonshot AI on Sep 5 2025.

When was GPT-5.5 released?

GPT-5.5 was released by OpenAI on Apr 23 2026.

Which is better on GPQA Diamond, Kimi K2 (0905) or GPT-5.5?

GPT-5.5 scores higher on GPQA Diamond — Kimi K2 (0905) 75.1% vs GPT-5.5 93.6%.

Is Kimi K2 (0905) or GPT-5.5 open source?

Kimi K2 (0905) is an open-source / open-weight model released by Moonshot AI. GPT-5.5 is a proprietary model released by OpenAI.

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Latest Release

GPT-5.5

Apr 23 2026

Home/Compare/Kimi K2 (0905) vs GPT-5.5

Kimi K2 (0905) vs GPT-5.5

1 vs 1 benchmarks won

	Moonshot AI Kimi K2 (0905)	OpenAI GPT-5.5
Overview
Company	Moonshot AI	OpenAI
Release date	Sep 5 2025	Apr 23 2026
Model type	—	—
Open source	Yes	No
Specifications
Parameters	1T	—
Context window	256k	—
Benchmarks
Science reasoning GPQA Diamond	75.1%	93.6%
Software engineering SWE-Bench Verified	65.8%	—
Multimodal understanding MMMU	—	—
Timeline
Release gap	Kimi K2 (0905) shipped 230 days before GPT-5.5

Which is better: Kimi K2 (0905) or GPT-5.5?

Kimi K2 (0905) and GPT-5.5 are evenly matched across the benchmarks they both publish. Kimi K2 (0905) shipped 230 days before GPT-5.5, so benchmark comparisons should account for the intervening progress.

Kimi K2 (0905) is an open-source / open-weight model; GPT-5.5 is proprietary.

On GPQA Diamond, GPT-5.5 scores 93.6%, 18.5 points above Kimi K2 (0905) at 75.1%.

Frequently asked questions

When was Kimi K2 (0905) released?: Kimi K2 (0905) was released by Moonshot AI on Sep 5 2025.
When was GPT-5.5 released?: GPT-5.5 was released by OpenAI on Apr 23 2026.
Which is better on GPQA Diamond, Kimi K2 (0905) or GPT-5.5?: GPT-5.5 scores higher on GPQA Diamond — Kimi K2 (0905) 75.1% vs GPT-5.5 93.6%.
Is Kimi K2 (0905) or GPT-5.5 open source?: Kimi K2 (0905) is an open-source / open-weight model released by Moonshot AI. GPT-5.5 is a proprietary model released by OpenAI.