GPT-5.6 Luna vs Kimi K3
OpenAI's GPT-5.6 Luna and Moonshot AI's Kimi K3 both target production language workloads, but they price and behave differently. Here is the side-by-side.
Pricing checked against provider documentation on . How we verify
The short answer
GPT-5.6 Luna is the cheaper option — roughly 13.3x less on a blended workload, and it suits high-volume work on a tight budget. Kimi K3 justifies its premium when you need natively multimodal long-horizon agents.
OpenAI • GPT-5.6
$0.20 / $1.20
/ 1M tokens (input / output)
After an 80% price cut in July 2026, Luna became the value outlier among frontier-family models: it outperforms the previous generation's top-end Opus tier on coding evals while costing about a fiftieth of Fable 5 per input token. This is the model to route bulk traffic through in a tiered architecture.
Moonshot AI • Kimi K
$3.00 / $15.00
/ 1M tokens (input / output)
At 2.8T total parameters with 104B active, Kimi K3 is the largest open-weight model in general circulation and the only one here that ingests video natively. Reasoning is always on with configurable effort. The licence is the catch: it is not a standard open licence, and organisations above $20M in revenue need a separate commercial agreement.
Input price
Kimi K3 is 15.0x the price than GPT-5.6 Luna on input tokens.
Output price
Kimi K3 is 12.5x the price than GPT-5.6 Luna on output tokens — usually the side that dominates the bill.
Monthly cost at three workload sizes
Standard (non-batch, non-cached) rates. Reasoning models will exceed these figures because thinking tokens bill as output.
| Workload | GPT-5.6 Luna | Kimi K3 | Difference |
|---|---|---|---|
| Light — 1M in / 200K out | $0 | $6 | $6 |
| Moderate — 10M in / 2M out | $4 | $60 | $56 |
| Heavy — 100M in / 20M out | $44 | $600 | $556 |
Specification comparison
| Attribute | GPT-5.6 Luna | Kimi K3 |
|---|---|---|
| Input (/ 1M tokens) | $0.20 | $3.00 |
| Output (/ 1M tokens) | $1.20 | $15.00 |
| Cached input | $0.02 | $0.30 |
| Context window | 1,048,576 tokens | 1,048,576 tokens |
| Max output | 128,000 tokens | 131,072 tokens |
| Native reasoning | Yes | Yes |
| Knowledge cutoff | 2026-02 | 2026-02 |
| Relative latency | low | high |
| Open weights | No | Kimi K3 License (commercial terms above $20M revenue) |
| API model ID | gpt-5.6-luna | kimi-k3 |
| Status | stable | stable |
GPT-5.6 Luna: Cut 80% from the $1/$6 launch price on 2026-07-30.
Kimi K3: The custom licence requires a separate commercial agreement once the licensee and its affiliates exceed $20M revenue over any consecutive 12 months.
Choose GPT-5.6 Luna if…
- Classification and content moderation
- High-frequency agent subtasks
- Bulk summarization
- Cost-sensitive chat features
Choose Kimi K3 if…
- Multimodal agent workflows
- Video and image understanding at length
- Ambitious long-horizon automation
- Research requiring open weights at scale
Frequently asked
Is GPT-5.6 Luna or Kimi K3 cheaper?
GPT-5.6 Luna is cheaper. On a blended 3:1 input-to-output workload it costs about 13.3x less than Kimi K3.
Which has the larger context window, GPT-5.6 Luna or Kimi K3?
Both accept up to 1.05M tokens, so context is not a differentiator here.
Should I use GPT-5.6 Luna or Kimi K3?
Pick GPT-5.6 Luna for high-volume work on a tight budget. Pick Kimi K3 for natively multimodal long-horizon agents. If cost dominates the decision, GPT-5.6 Luna wins; if you need the capability ceiling, benchmark both on your own evals before committing.