Claude Opus 4 vs Kimi K2 (0905)
Anthropic Claude Opus 4 | Moonshot AI Kimi K2 (0905) | |
|---|---|---|
| Overview | ||
| Company | Anthropic | Moonshot AI |
| Release date | May 22 2025 | Sep 5 2025 |
| Access | Proprietary | Open Weight |
| Specifications | ||
Parameters | — | 1T |
Context window | — | 256k |
| Benchmarks | ||
Nonsense detection BullshitBench v2Given a confidently-worded but nonsensical prompt, does the AI spot that it makes no sense and push back — instead of playing along and inventing an answer? The score is how often it clearly called out the nonsense. Higher is better. | 34% | — |
Coding SWE-Bench VerifiedReal coding tasks pulled from open-source projects — the AI has to find and fix actual bugs. A human-checked version of the original SWE-Bench. Higher is better. | 72.5%Best | 65.8% |
Science GPQA DiamondGraduate-level science questions in biology, physics, and chemistry — hard enough that subject-matter PhDs score around 65%. Higher is better. | 79.6%Best | 75.1% |
| Timeline | ||
| Release gap | Claude Opus 4 shipped 106 days before Kimi K2 (0905) | |
Which is better: Claude Opus 4 or Kimi K2 (0905)?
Claude Opus 4 leads Kimi K2 (0905) on 2 of the 2 benchmarks they both report (SWE-Bench Verified, GPQA Diamond). Claude Opus 4 shipped 106 days before Kimi K2 (0905), so benchmark comparisons should account for the intervening progress.
Claude Opus 4 is proprietary, while Kimi K2 (0905) is open weight.
On SWE-Bench Verified, Claude Opus 4 leads at 72.5% vs Kimi K2 (0905) at 65.8%. On GPQA Diamond, Claude Opus 4 leads at 79.6% vs Kimi K2 (0905) at 75.1%.
Frequently asked questions
Claude Opus 4 was released by Anthropic on May 22 2025.
Kimi K2 (0905) was released by Moonshot AI on Sep 5 2025.
Claude Opus 4 leads on SWE-Bench Verified — Claude Opus 4 72.5% vs Kimi K2 (0905) 65.8%.
Claude Opus 4 leads on GPQA Diamond — Claude Opus 4 79.6% vs Kimi K2 (0905) 75.1%.
Claude Opus 4 is a proprietary model released by Anthropic. Kimi K2 (0905) is an open weight model released by Moonshot AI.