Claude Opus 4.7 vs Kimi K3
Pricing, context window and real answers (August 2026)
Claude Opus 4.7 (Anthropic) and Kimi K3 (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
 Claude Opus 4.7 |  Kimi K3 | |
|---|---|---|
| Provider | Anthropic | Moonshot |
| Input (per 1M tokens) | ¥840 | ¥536.1 |
| Output (per 1M tokens) | ¥4,200 | ¥2,680.5 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥2,940 | ¥1,876 |
| Context window | 1,000,000 tokens | 1,048,576 tokens |
| Release date | 4/16/2026 | 7/16/2026 |
| Input modalities | text, image, file | text, image |
| Arena · overall | #6 · ELO 1,494 | #10 · ELO 1,489 |
| Arena · Japanese | #18 · ELO 1,478 | #4 · ELO 1,510 |
| Arena · coding | #4 · ELO 1,547 | #6 · ELO 1,543 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, Kimi K3: ¥2,680.5 per 1M output tokens, 36% less than Claude Opus 4.7.
- On the Overall arena board, Claude Opus 4.7 ranks higher (#6; Kimi K3 is #10).
- On the Japanese arena board, Kimi K3 ranks higher (#4; Claude Opus 4.7 is #18).
- On the Coding arena board, Claude Opus 4.7 ranks higher (#4; Kimi K3 is #6).
- For long documents, Kimi K3: a 1,048,576-token context window against 1,000,000 for Claude Opus 4.7.
- 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, Claude Opus 4.7 or Kimi K3?
- Per 1M output tokens, Claude Opus 4.7 is ¥4,200 and Kimi K3 is ¥2,680.5 on FastMetal (yen, before tax), so Kimi K3 is cheaper.
- How do the context windows of Claude Opus 4.7 and Kimi K3 compare?
- Claude Opus 4.7 takes 1,000,000 tokens; Kimi K3 takes 1,048,576.
- Which ranks higher, Claude Opus 4.7 or Kimi K3?
- Kimi K3 ranks higher on the public arena (Claude Opus 4.7 #18, Kimi K3 #4). Ranks move as the leaderboard updates.
- Can I use Claude Opus 4.7 and Kimi K3 with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-opus-4-7" or "kimi-k3" 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 Claude Opus 4.7 and Kimi K3 from the browser chat and the API. No monthly fee.