Claude Fable 5.1 vs Muse Spark 1.3 Contributor
Pricing, context window and real answers (September 2026)
Claude Fable 5.1 (Anthropic) and Muse Spark 1.3 Contributor (Meta), 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 |  Muse Spark 1.3 Contributor | |
|---|---|---|
| Provider | Anthropic | Meta |
| Input (per 1M tokens) | ¥1,787 | ¥17.59 |
| Output (per 1M tokens) | ¥8,935 | ¥35.18 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥6,255 | ¥35 |
| Context window | 1,000,000 tokens | 1,048,576 tokens |
| Release date | 9/1/2026 | 9/2/2026 |
| Input modalities | text, image, file | text, image, video, file, audio |
| Throughput (p50) | — | — |
| Arena · overall | #5 · ELO 1,498 | Unranked |
| Arena · Japanese | Unranked | Unranked |
| Arena · coding | #32 · ELO 1,519 | Unranked |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, Muse Spark 1.3 Contributor: ¥35.18 per 1M output tokens, 100% less than Claude Fable 5.1.
- For long documents, Muse Spark 1.3 Contributor: a 1,048,576-token context window against 1,000,000 for Claude Fable 5.1.
- 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 Muse Spark 1.3 Contributor?
- Per 1M output tokens, Claude Fable 5.1 is ¥8,935 and Muse Spark 1.3 Contributor is ¥35.18 on FastMetal (yen, before tax), so Muse Spark 1.3 Contributor is cheaper.
- How do the context windows of Claude Fable 5.1 and Muse Spark 1.3 Contributor compare?
- Claude Fable 5.1 takes 1,000,000 tokens; Muse Spark 1.3 Contributor takes 1,048,576.
- Can I use Claude Fable 5.1 and Muse Spark 1.3 Contributor with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-fable-5-1" or "muse-spark-1.3-contributor" 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 Muse Spark 1.3 Contributor from the browser chat and the API. No monthly fee.