Claude Mythos 5.1 vs Muse Spark 1.3
Claude Mythos 5.1 from Anthropic and Muse Spark 1.3 from Meta, side by side. Every figure comes from the model registry. No markup on model usage: you pay the provider's list price.
| Attribute |   Claude Mythos 5.1 |  Muse Spark 1.3 |
|---|---|---|
| Provider | Anthropic | Meta |
| Model id | anthropic/claude-mythos-5-1 | meta/muse-spark-1.3 |
| Status | Available via Safeguard | Available via Safeguard |
| Input / 1M tokens | $10 | $1.25 |
| Output / 1M tokens | $50 | $4.25 |
| Price notes | Base price, same as Claude Fable 5.1. Anthropic requires the organization to be verified through one of its programs before use. Cache hits $0.25/1M. Batch 50% off. | Standard tier (no training on your data). Cached input $0.15. No long-context premium. Contributor tier (muse-spark-1.3-contributor) is $0.10 / $0.20 in exchange for allowing training. Audio input not fully supported on 1.3. |
| Context | 1M | 1.05M |
| Parameters | Not published | Not published |
| Max output | 128,000 tokens | Not published |
| Modality | Text and image | Text and image |
| Weights | Closed | Closed |
| Zero data retention | Not offered | Not stated |
| Prompts go to | Anthropic (global routing by default) | Meta (Meta Model API) |
| Retention | Not used for model training without express permission. Claude Mythos 5.1 is a Covered Model that requires 30-day data retention and is not available under ZDR unless Anthropic expressly authorizes it | Standard tier: prompts and completions not used to train Meta models, Contributor tier allows training in exchange for lower prices. No retention period published in the API docs |
| Region | Global by default, US-only inference via inference_geo at 1.1x pricing (Claude 4.6 and later) | Not stated |
| Price checked | 2026-10-08 | 2026-10-08 |
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