Side by side
Standard-tier prices in effect today. The better value in each row is highlighted.
| Fact | Claude Fable 5.1 | Claude Mythos 5.1 |
|---|---|---|
| Price per 1M input tokens | $10 | $10 |
| Price per 1M output tokens | $50 | $50 |
| Cost of 10M input and 2M output tokens | $200 | $200 |
| Arena Text | 1501 Elo (#3 of 39) | Not measured |
| FrontierMath Tiers 1-3 (v2) | 90.2% (#4 of 37) | Not measured |
| SimpleQA Verified | 70.8% (#5 of 34) | Not measured |
| Provider | Anthropic | Anthropic |
| Release date | September 1, 2026 | September 1, 2026 |
| Access | API only | API only |
| Context window | 1,000,000 tokens | Not reported |
| Max output | 128,000 tokens | Not reported |
| Input | text, image | text, image |
| Output | text | text |
When to choose each
Claude Fable 5.1
Best for
- Long-horizon agentic coding where a large prompt prefix is replayed across many turns
- Work where Claude Opus 5 at higher effort has already been evaluated and fell short
Watch out for
- Base input and output pricing is unchanged from Fable 5 at $10 / $50; the saving is entirely in cache reads, so a workload with little cache reuse sees no discount
- The 4.7-generation tokenizer produces roughly 30% more tokens for the same text than Claude Sonnet 4.6 and earlier, so per-token rates are not directly comparable across generations
- Anthropic’s launch comparisons are self-reported and were not reproduced independently here
Claude Mythos 5.1
Best for
- Organisations already admitted to Anthropic’s limited-availability programme that need frontier capability at Fable 5.1 rates
Watch out for
- Limited availability: access is restricted to organisations vetted through Anthropic’s Glasswing programme, so it cannot be assumed available for a general evaluation
- Anthropic’s public model comparison table does not list a context window or maximum output for Mythos 5.1, so both are recorded as unknown here rather than inferred from Fable 5.1
Claude Fable 5.1 vs Claude Mythos 5.1 FAQ
Which is cheaper, Claude Fable 5.1 or Claude Mythos 5.1?
Both cost $10 per 1M input tokens. For 10M input and 2M output tokens, Claude Fable 5.1 costs $200 and Claude Mythos 5.1 $200 at standard rates.
Related comparisons
Production evaluation
Choosing between Claude Fable 5.1 and Claude Mythos 5.1?
Public benchmarks narrow the shortlist. We run both on your own tasks, data and cost limits, then build the routing and review controls to run the winner in production.
- A head-to-head evaluation on your real workload
- Routing between models by cost and difficulty