Claude Sonnet 4.5vsKimi K2 (0905)
Claude Sonnet 4.5 | 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 | ||
Input priceWhat you pay for everything you send the model — your question, plus any documents or earlier conversation you include with it. | $3.00 | — |
Output priceWhat you pay for the text the model writes back. It is normally the dearer half: producing an answer costs more than reading one. | $15.00 | — |
Cached input priceA reduced rate for text you send over and over. If every request starts with the same instructions or the same document, the provider keeps a copy ready and charges less to read it again. | $0.30 | — |
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. | $3.00Amazon 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. | $15.00Amazon 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. | 77.2% | 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. | 83.4% | 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. | 79% | — |
Next.js EvalsNext.js coding — Vercel's open eval of how well AI coding agents build and migrate real Next.js apps — measured as the share of tasks the agent completes successfully. Higher is better. | 46% | — |
MMMUMultimodal — Tests the AI on understanding images and text together across many college subjects. Higher is better. | 68% | — |
| Overview | ||
| Company | Anthropic | Moonshot AI |
| Release date | Sep 29 2025 | Sep 5 2025 |
| Access | Proprietary | Open Weight |
Other comparisons
Frequently asked questions
Claude Sonnet 4.5 leads Kimi K2 (0905) on 2 of the 2 benchmarks they both report (SWE-Bench Verified, GPQA Diamond). Only Claude Sonnet 4.5 has a verified first-party API price: $3.00 per million input tokens and $15.00 per million output tokens. No pay-as-you-go API rate is tracked for Kimi K2 (0905). Kimi K2 (0905) shipped 24 days before Claude Sonnet 4.5, so benchmark comparisons should account for the intervening progress.
Claude Sonnet 4.5 is proprietary, while Kimi K2 (0905) is open weight.
On SWE-Bench Verified, Claude Sonnet 4.5 leads at 77.2% vs Kimi K2 (0905) at 65.8%. On GPQA Diamond, Claude Sonnet 4.5 leads at 83.4% vs Kimi K2 (0905) at 75.1%.
Claude Sonnet 4.5 was released by Anthropic on Sep 29 2025.
Kimi K2 (0905) was released by Moonshot AI on Sep 5 2025.
Claude Sonnet 4.5 leads on SWE-Bench Verified — Claude Sonnet 4.5 77.2% vs Kimi K2 (0905) 65.8%.
Claude Sonnet 4.5 leads on GPQA Diamond — Claude Sonnet 4.5 83.4% vs Kimi K2 (0905) 75.1%.
Only Claude Sonnet 4.5 has a verified first-party API price: $3.00 per million input tokens and $15.00 per million output tokens. No pay-as-you-go API rate is tracked for Kimi K2 (0905). Rates are pay-as-you-go API prices verified on August 18, 2026.
Claude Sonnet 4.5 is a proprietary model released by Anthropic. Kimi K2 (0905) is an open weight model released by Moonshot AI.