Kimi K3.1 Pro vs Claude Opus 5.5: API pricing and open weights
Pro costs less than Opus on the half-cached example request. Pro's open weights add a third party host, listed at $0.3287 input and $8.115 output. Opus has no weights to host, and Pro's license needs a read before commercial use.
Kimi K3.1 Pro publishes its weights and Claude Opus 5.5 doesn't, and that changes what you can do about price. On the API, Pro lists 50% less than Opus for input and 50% less for output. Opus has no published weights, so you can't host it yourself. Pro can come from third party hosts, or from your own cluster if you have one. For agent work that sends the same long prefix thousands of times, the cache read rate matters as much as either headline number. This page prices that case and the open weights question side by side.
Compare agent session costs, cache reads and writes, and what open weights add.
By TechCompare · Updated
MoonshotAI: Kimi K3.1 Pro
Moonshot AI's own price
- Input
- $2
- Output
- $10
- Cached
- $0.20
per 1M tokens
Price checked 2026-11-07
Anthropic: Claude Opus 5.5
Anthropic's own price
- Input
- $4
- Output
- $20
- Cached
- $0.20
per 1M tokens
Price checked 2026-11-07
Cost Comparison
Based on 100,000 input tokens (50% cached), 5,000 output tokens, and 100 requests.Prices come live from OpenRouter at each maker's own price where it's listed. Temporary deals are left out.
Side-by-side specs
| Spec | Kimi K3.1 Pro | Claude Opus 5.5 |
|---|---|---|
| Standard input per 1M tokens | $2.00 (better on this spec) | $4.00 |
| Standard output per 1M tokens | $10.00 (better on this spec) | $20.00 |
| Cache reads per 1M tokens | $0.20 | $0.20 |
| 100K input + 5K output, no cache hits | $0.25 (better on this spec) | $0.50 |
| 100K input + 5K output, half the input cached | $0.16 (better on this spec) | $0.31 |
| Agent session, 40 turns, mostly cached | $3.48 (better on this spec) | $5.88 |
| Long prompt rates, input / output per 1M | No separate tier | No separate tier |
| Batch input / output per 1M | None | $2.00 / $10.00 |
| Third party host, input / output per 1M | $0.3287 / $8.115 | None listed |
| Context window | 1,048,576 tokens | 1,000,000 tokens |
| Weights | Open, custom license | Closed |
How they differ
Kimi K3.1 Pro charges $2 per million input tokens, $10 per million output tokens and $0.20 for cache reads. Claude Opus 5.5 charges $4, $20 and $0.20. At 100,000 input tokens and 5,000 output tokens, a request costs $0.25 on Pro and $0.50 on Opus with nothing cached, or $0.16 and $0.31 with half the input read from cache. A coding agent session shows the cache effect. Take 40 turns, each sending 150,000 input tokens with nearly all of it cached and producing 3,000 output tokens. That costs $3.48 on Pro and $5.88 on Opus. Cache reads cost the same on both, so the gap comes from uncached input and output. Opus also charges to create a cache. A five minute write costs $5 per million tokens, and a one hour write costs $8. Those writes aren't in the session estimate above. Opus lists no separate long prompt rate. Opus lists batch prices and Pro doesn't. An overnight job of 5,000 documents at 20,000 input tokens and 1,500 output tokens each costs $275 on Opus with batch and $275 on Pro at standard rates. The embedded calculator uses live OpenRouter rates, which can depend on provider routing.
Verdict
Decide on a measured agent task, not on the rate card. On price alone, Pro has the edge at every cache share, so Opus has to finish enough extra tasks, or need enough fewer retries, to justify its rates. Open weights give you options that a closed model can't, which are a choice of host, a cluster you control, and an exit if terms change. They also give you work, since you own the serving setup, quantization checks and license review. If you only plan to call an API, that extra freedom is worth less than the measured cost of an accepted result.
Which should you pick?
Choose Kimi K3.1 Pro
Pick Pro when you want a choice of where it runs, or when your sessions are long and cache heavy. It takes text, image and video input, supports tools and reasoning, and has a 1,048,576 token context. A third party host lists it at $0.3287 input and $8.115 output with fp4 weights, so test that host on your tasks before you rely on it. The license is custom, so read it before commercial use. Teams that may self host can size the cluster with the VRAM calculator before they commit.
Kimi K3.1 Pro on Hugging FaceChoose Claude Opus 5.5
Pick Opus when your tested agent tasks finish with fewer errors or less human review on it, or when you want one vendor for the model and its billing. It's a closed model, so there are no weights to host yourself. Its context window is 1,000,000 tokens. Plan for cache writes at $5 per million tokens for five minutes, since every cache that expires gets billed again when it's rebuilt. Confirm its supported input types on Anthropic's pricing and model pages, because this page doesn't list them.
Anthropic's pricing rules