GPT-5.6 Luna vs Kimi K2.7 Code
Pricing, context window and real answers (August 2026)
GPT-5.6 Luna (OpenAI) and Kimi K2.7 Code (Moonshot), compared as you can actually call them on FastMetal. Both are served from the same OpenAI-compatible endpoint and API key; switching is a change to the model string.
Specs and pricing
 GPT-5.6 Luna |  Kimi K2.7 Code | |
|---|---|---|
| Provider | OpenAI | Moonshot |
| Input (per 1M tokens) | ¥35.74 | ¥55 |
| Output (per 1M tokens) | ¥214.44 | ¥530 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥143 | ¥320 |
| Context window | 1,050,000 tokens | 262,144 tokens |
| Release date | 7/9/2026 | 6/12/2026 |
| Input modalities | file, image, text | text, image |
| Arena · overall | #63 · ELO 1,452 | Unranked |
| Arena · Japanese | #36 · ELO 1,444 | Unranked |
| Arena · coding | #69 · ELO 1,496 | Unranked |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, GPT-5.6 Luna: ¥214.44 per 1M output tokens, 60% less than Kimi K2.7 Code.
- For long documents, GPT-5.6 Luna: a 1,050,000-token context window against 262,144 for Kimi K2.7 Code.
- If in doubt, try both on the same key. Switching is a change to the model string, and each is billed at its own rate.
Frequently asked questions
- Which is cheaper, GPT-5.6 Luna or Kimi K2.7 Code?
- Per 1M output tokens, GPT-5.6 Luna is ¥214.44 and Kimi K2.7 Code is ¥530 on FastMetal (yen, before tax), so GPT-5.6 Luna is cheaper.
- How do the context windows of GPT-5.6 Luna and Kimi K2.7 Code compare?
- GPT-5.6 Luna takes 1,050,000 tokens; Kimi K2.7 Code takes 262,144.
- Can I use GPT-5.6 Luna and Kimi K2.7 Code with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "gpt-5.6-luna" or "japan-kimi-k2.7-code" as the model. Each is billed at its own rate from the same prepaid balance.
Try both on one API key
Create an account and add credit to call GPT-5.6 Luna and Kimi K2.7 Code from the browser chat and the API. No monthly fee.