Claude Sonnet 4.5 vs Kimi K2 Thinking
Benchmarks, API pricing and specs, head to head. Data updated 2026-06-10.
Anthropic · Sep 2025
The model that made 30-hour autonomous coding sessions real — 77.2% SWE-bench Verified and a 1M-token context beta at $3/$15.
Moonshot AI · Nov 2025
A trillion-parameter open reasoning agent that can chain 200–300 tool calls — the open-weights agentic standout of late 2025.
The verdict
Kimi K2 Thinking wins 3 of the 5 benchmarks these models share, against 2 for Claude Sonnet 4.5. On price the gap is dramatic: Kimi K2 Thinking works out roughly 5.6x cheaper per blended million tokens. Kimi K2 Thinking also takes 262K of context versus 200K for Claude Sonnet 4.5. And Kimi K2 Thinking is open-weights (Modified MIT), so it can be self-hosted — a structural advantage if data control or vendor independence matters.
Benchmark head-to-head 2–3
Specs & pricing
| Claude Sonnet 4.5 | Kimi K2 Thinking | |
|---|---|---|
| modhub Index | 65.5 | 67.6 |
| Input price / 1M | $3 | $0.6 |
| Output price / 1M | $15 | $2.5 |
| Context window | 200K | 262K |
| Max output | 64K | — |
| Open weights | no | yes (Modified MIT) |
| Reasoning model | yes | yes |
| Multimodal input | text, image | text |
| Knowledge cutoff | Jan 2025 | Apr 2025 |
| Released | Sep 2025 | Nov 2025 |
| Example monthly cost* | $52.50 | $9.75 |
* 10M input + 1.5M output tokens per month at list prices, no caching. Green = better value on that row.
Frequently asked questions
- Which is better, Claude Sonnet 4.5 or Kimi K2 Thinking?
- Kimi K2 Thinking wins 3 of the 5 benchmarks these models share, against 2 for Claude Sonnet 4.5. On price the gap is dramatic: Kimi K2 Thinking works out roughly 5.6x cheaper per blended million tokens. Kimi K2 Thinking also takes 262K of context versus 200K for Claude Sonnet 4.5. And Kimi K2 Thinking is open-weights (Modified MIT), so it can be self-hosted — a structural advantage if data control or vendor independence matters.
- Which is cheaper, Claude Sonnet 4.5 or Kimi K2 Thinking?
- Claude Sonnet 4.5 costs $3/$15 per million input/output tokens, while Kimi K2 Thinking costs $0.6/$2.5. For a typical workload of 10M input and 1.5M output tokens per month, that's $52.50 versus $9.75.
- Which model is better for coding, Claude Sonnet 4.5 or Kimi K2 Thinking?
- On SWE-bench Verified — the standard agentic-coding benchmark — Claude Sonnet 4.5 scores 77.2% versus 71.3% for Kimi K2 Thinking, making Claude Sonnet 4.5 the stronger pick for coding agents.