Claude Opus 4.1vsKimi K2 (0905)
Claude Opus 4.1 | Kimi K2 (0905) | |
|---|---|---|
| Specifications | ||
ParametersA rough measure of how big the model is. More parameters usually means more capable and more expensive to run, though it is a poor guide on its own — a smaller, newer model often beats a larger, older one. | — | 1T |
Context windowHow much text the model can hold in mind at once — your question, any documents you attach, the conversation so far, and its own reply. Go past it and the earliest part falls out of view. | — | 256k |
| API pricingUSD per 1M tokens · lower wins | ||
Cheapest inputLowest input rate across third-party providers, excluding the lab itself. The cheapest endpoint may run a quantised build or a shorter context — see "Available from" on the model page. | $15.00Amazon Bedrock | $0.60Novita |
Cheapest outputLowest output rate across third-party providers, excluding the lab itself. May come from a different provider than the cheapest input. | $75.00Amazon Bedrock | $2.50Novita |
| Benchmarks | ||
SWE-Bench VerifiedCoding — Real 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. | 74.5% | 65.8% |
GPQA DiamondScience — Graduate-level science questions in biology, physics, and chemistry — hard enough that subject-matter PhDs score around 65%. Higher is better. | 80.9% | 75.1% |
| BenchmarksPublished by one model only | ||
BullshitBench v2Nonsense detection — Given 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. | 43% | — |
| Overview | ||
| Company | Anthropic | Moonshot AI |
| Release date | Aug 5 2025 | Sep 5 2025 |
| Access | Proprietary | Open Weight |
Other comparisons
Frequently asked questions
Claude Opus 4.1 leads Kimi K2 (0905) on 2 of the 2 benchmarks they both report (SWE-Bench Verified, GPQA Diamond). Claude Opus 4.1 shipped 31 days before Kimi K2 (0905), so benchmark comparisons should account for the intervening progress.
Claude Opus 4.1 is proprietary, while Kimi K2 (0905) is open weight.
On SWE-Bench Verified, Claude Opus 4.1 leads at 74.5% vs Kimi K2 (0905) at 65.8%. On GPQA Diamond, Claude Opus 4.1 leads at 80.9% vs Kimi K2 (0905) at 75.1%.
Claude Opus 4.1 was released by Anthropic on Aug 5 2025.
Kimi K2 (0905) was released by Moonshot AI on Sep 5 2025.
Claude Opus 4.1 leads on SWE-Bench Verified — Claude Opus 4.1 74.5% vs Kimi K2 (0905) 65.8%.
Claude Opus 4.1 leads on GPQA Diamond — Claude Opus 4.1 80.9% vs Kimi K2 (0905) 75.1%.
Claude Opus 4.1 is a proprietary model released by Anthropic. Kimi K2 (0905) is an open weight model released by Moonshot AI.