Claude Fable 5.1 vs Claude Opus 4.7
Pricing, context window and real answers (September 2026)
Claude Fable 5.1 (Anthropic) and Claude Opus 4.7 (Anthropic), 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 Fable 5.1 | Claude Opus 4.7 | |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Input (per 1M tokens) | ¥1,787 | ¥840 |
| Output (per 1M tokens) | ¥8,935 | ¥4,200 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥6,255 | ¥2,940 |
| Context window | 1,000,000 tokens | 1,000,000 tokens |
| Release date | 9/1/2026 | 4/16/2026 |
| Input modalities | text, image, file | text, image, file |
| Arena · overall | #3 · ELO 1,504 | #7 · ELO 1,494 |
| Arena · Japanese | Unranked | #17 · ELO 1,478 |
| Arena · coding | #34 · ELO 1,517 | #4 · ELO 1,547 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, Claude Opus 4.7: ¥4,200 per 1M output tokens, 53% less than Claude Fable 5.1.
- On the Overall arena board, Claude Fable 5.1 ranks higher (#3; Claude Opus 4.7 is #7).
- On the Coding arena board, Claude Opus 4.7 ranks higher (#4; Claude Fable 5.1 is #34).
- 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 Fable 5.1 or Claude Opus 4.7?
- Per 1M output tokens, Claude Fable 5.1 is ¥8,935 and Claude Opus 4.7 is ¥4,200 on FastMetal (yen, before tax), so Claude Opus 4.7 is cheaper.
- How do the context windows of Claude Fable 5.1 and Claude Opus 4.7 compare?
- Claude Fable 5.1 takes 1,000,000 tokens; Claude Opus 4.7 takes 1,000,000.
- Which ranks higher, Claude Fable 5.1 or Claude Opus 4.7?
- Claude Fable 5.1 ranks higher on the public arena (Claude Fable 5.1 #3, Claude Opus 4.7 #17). Ranks move as the leaderboard updates.
- Can I use Claude Fable 5.1 and Claude Opus 4.7 with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-fable-5-1" or "anthropic-claude-opus-4-7" 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 Fable 5.1 and Claude Opus 4.7 from the browser chat and the API. No monthly fee.