AI Agent Choices
Kimi K3 vs ChatGPT vs Claude: API Costs and Tradeoffs
Kimi K3 is not the cheapest current API option in this comparison. GPT-6.1 Sol and Claude Sonnet 5.5 both list lower standard input and output prices. Kimi's distinct advantage is that its weights are available, while the other two remain proprietary. The useful question is which model completes your workload reliably at an acceptable total cost.
Affiliate disclosure: links to Kimi are sponsored. We may earn a commission at no cost to you. Prices and specifications were checked against provider sources on October 2, 2026.
Current specifications and prices
| Feature | Kimi K3 | GPT-6.1 Sol | Claude Sonnet 5.5 |
|---|---|---|---|
| Vendor | Moonshot AI | OpenAI | Anthropic |
| Current release | July 16, 2026 | September 29, 2026 | September 28, 2026 |
| Context window | 1,000,000 tokens | 1,050,000 tokens | 1,000,000 tokens |
| API input | $3.00 / 1M | $2.00 / 1M | $2.00 / 1M |
| Cached input | $0.30 / 1M | $0.10 / 1M | $0.20 / 1M |
| API output | $15.00 / 1M | $10.00 / 1M | $10.00 / 1M |
| Access | Kimi API, Kimi.com, Kimi Work, Kimi Code | Responses API and Chat Completions | Claude API and partner cloud platforms |
| Open weights | Yes, released July 27, 2026 | No | No |
| Provider positioning | Coding, knowledge work, reasoning, and long-context agent tasks | Near-Astra performance at lower cost for complex work | Speed and intelligence for general production work |
These are list prices, not a quote. OpenAI states that GPT-6.1 Sol requests above 272,000 input tokens use higher input and output rates. Tool calls, caching, batch processing, regional inference, taxes, and negotiated contracts can also change the total.
A cost example you can verify
Take one agent run that sends 100,000 uncached input tokens and receives 20,000 output tokens. This stays below OpenAI's long-context pricing threshold. At the listed standard rates, the token cost is:
Kimi K3
$0.60
$0.30 input plus $0.30 output
GPT-6.1 Sol
$0.40
$0.20 input plus $0.20 output
Claude Sonnet 5.5
$0.40
$0.20 input plus $0.20 output
This calculation isolates token list price. It does not claim equal output quality, latency, or retry rates. A cheaper call can cost more per completed task if it needs more tokens or more retries.
How to choose without guessing
Start with ten to twenty tasks that resemble your real agent workload. Keep the tools, success criteria, and input data fixed. Record whether each model completes the task, how long it takes, how many retries it needs, and what the full run costs. Token rates tell you the price of model usage. They do not tell you the price of a successful outcome.
Choose Kimi K3 when open weights or the Kimi ecosystem matter
Moonshot released the Kimi K3 model weights on July 27, 2026. That makes Kimi the only option here when access to the weights is a requirement. It can also be a sensible choice when Kimi's own products or your task-level evaluation favor it. It is not the lowest-priced API in this three-model comparison. Before using business data, review the service terms, processing region, retention, security controls, and your organization's approval requirements.
Open Kimi K3 and run the same prompts you plan to use in production. Do not treat a provider benchmark as a substitute for that test.
Choose GPT-6.1 Sol when its tools fit your stack
OpenAI describes GPT-6.1 Sol as a balance of intelligence and cost for complex work. It supports the Responses API and built-in tools including web search, file search, code execution, computer use, and MCP. Its 1,050,000-token context window is slightly larger than the other two, but requests above 272,000 input tokens use higher rates. Model cost and tool cost should be estimated together.
Choose Claude Sonnet 5.5 when speed and Claude tooling fit
Anthropic describes Sonnet 5.5 as its best combination of speed and intelligence. Its standard input and output rates match GPT-6.1 Sol in this comparison. Claude-specific behavior, tool integration, latency, and task quality still need to be tested on your workflow. Matching token prices do not imply matching total cost or output quality.
What changed in this comparison
The earlier version compared Kimi K3 with stale GPT-5 and Claude Fable 5 details, and overstated Kimi's price advantage. This revision uses GPT-6.1 Sol and Claude Sonnet 5.5, the current balanced alternatives recommended by their providers. It replaces the unsupported multiplier with a worked calculation and links every material specification to a current provider source. We have not run a private benchmark, so we do not present provider benchmark scores as our own test results.
Provider sources checked October 2, 2026
- Moonshot AI: Kimi K3 technical and pricing overview
- Kimi Help Center: API billing guide
- OpenAI: GPT-6.1 Sol model and pricing
- Anthropic: Claude Sonnet 5.5 model and pricing
Related comparisons on this site
FAQ
Which of these three models has the lowest published API price? +
GPT-6.1 Sol and Claude Sonnet 5.5 tie at $2 per million input tokens and $10 per million output tokens. Kimi K3 lists $3 and $15. Cache use, batch discounts, tools, and long-context pricing can change the final bill.
Is Kimi K3 really 5 to 10 times cheaper than ChatGPT and Claude? +
No. In our worked example with 100,000 uncached input tokens and 20,000 output tokens, Kimi K3 costs $0.60, while GPT-6.1 Sol and Claude Sonnet 5.5 each cost $0.40 at the listed standard rates. Your workload may produce a different ratio.
Which model has the largest context window? +
GPT-6.1 Sol lists a 1,050,000-token context window. Kimi K3 and Claude Sonnet 5.5 each list 1,000,000 tokens. OpenAI applies higher rates when GPT-6.1 Sol input exceeds 272,000 tokens, so context size and context cost should be evaluated together.
Can I self-host any of these models? +
Kimi released the K3 model weights on July 27, 2026. GPT-6.1 Sol and Claude Sonnet 5.5 are proprietary API models. Open weights do not make K3 inexpensive to host, so estimate hardware, operations, and utilization before choosing self-hosting.
Which model should I use for an AI agent? +
Run the same representative tasks on all serious candidates. Measure completion quality, tool reliability, latency, retries, token use, and total cost. Published benchmarks and token prices are useful filters, but they do not replace an evaluation with your own tools and data.
Test Kimi K3 on your own workload
Use the same tasks and success criteria you will use in production.
Open Kimi K3