GPT-5.5 vs Kimi K2 Thinking
Benchmarks, API pricing and specs, head to head. Data updated 2026-06-10.
OpenAI · Apr 2026
OpenAI's flagship reasoning model with a 1M-token context window, built for hard coding, science and long-horizon agentic work.
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
GPT-5.5 wins 4 of the 4 benchmarks these models share, against 0 for Kimi K2 Thinking. On price the gap is dramatic: Kimi K2 Thinking works out roughly 10x cheaper per blended million tokens. GPT-5.5 also takes 1M of context versus 262K for Kimi K2 Thinking. 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 4–0
Specs & pricing
| GPT-5.5 | Kimi K2 Thinking | |
|---|---|---|
| modhub Index | 77.2 | 67.6 |
| Input price / 1M | $5 | $0.6 |
| Output price / 1M | $30 | $2.5 |
| Context window | 1M | 262K |
| Max output | 128K | — |
| Open weights | no | yes (Modified MIT) |
| Reasoning model | yes | yes |
| Multimodal input | text, image | text |
| Knowledge cutoff | Jan 2026 | Apr 2025 |
| Released | Apr 2026 | Nov 2025 |
| Example monthly cost* | $95.00 | $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, GPT-5.5 or Kimi K2 Thinking?
- GPT-5.5 wins 4 of the 4 benchmarks these models share, against 0 for Kimi K2 Thinking. On price the gap is dramatic: Kimi K2 Thinking works out roughly 10x cheaper per blended million tokens. GPT-5.5 also takes 1M of context versus 262K for Kimi K2 Thinking. 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, GPT-5.5 or Kimi K2 Thinking?
- GPT-5.5 costs $5/$30 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 $95.00 versus $9.75.
- Which model is better for coding, GPT-5.5 or Kimi K2 Thinking?
- On SWE-bench Verified — the standard agentic-coding benchmark — GPT-5.5 scores 82.6% versus 71.3% for Kimi K2 Thinking, making GPT-5.5 the stronger pick for coding agents.