Claude Fable 5.1 and Mythos 5.1
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Two access configurations of the same underlying model. Fable is generally available; Mythos uses different safeguards for approved specialist work. The official announcement gives a month without an exact day.
- Reviewed tasks
- Coding, Knowledge work, Research
- Reviewed modalities
- Text, Images
- Deployment paths
- Hosted API
- Focus / inputs
- Fable: text and images → text. Mythos input support is not independently documented here.
- Availability / restrictions
- Fable 5.1: Claude API and supported cloud platforms. Mythos 5.1: restricted trusted access programs and Claude Security; it is not a generally available API alternative.
- Licence category
- Provider terms
- Licence / terms
- Proprietary; provider terms and access restrictions apply.
Variants, limits and list prices
Values are copied from the linked first-party pages as stated, with the date each group was checked. Unknown means the pages checked do not state the value. Prices are list prices, not a quote or a ranking.
| Field | Claude Fable 5.1 | Claude Mythos 5.1 |
|---|---|---|
| API identifier | claude-fable-5-1 | Unknown |
| Released | Unknown | |
| Status and retirement | Retirement not before . | Unknown |
| Lifecycle checked | Checked | Checked |
| Context window | 1M tokens | 1M tokens |
| Max input | Unknown | Unknown |
| Max output | 128K tokens | 128K tokens |
| Rate limits | Unknown | Unknown |
| Limit notes | Unknown | Shared with Fable 5.1, as stated on the pricing page. |
| Limits checked | Checked | Checked |
| Base input price | 10 USD/MTok (Standard) | 10 USD/MTok (Standard) |
| Base output price | 50 USD/MTok (Standard) | 50 USD/MTok (Standard) |
| Cache-read price | 0.25 USD/MTok (Standard) | 0.25 USD/MTok (Standard) |
| Price conditions | Standard: input 10 USD/MTok, output 50 USD/MTok, cache read 0.25 USD/MTok, cache write 12.5 USD/MTok (5 minutes), cache write 20 USD/MTok (1 hour). 50% off input and output with the Batch API. | Standard: input 10 USD/MTok, output 50 USD/MTok, cache read 0.25 USD/MTok, cache write 12.5 USD/MTok (5 minutes), cache write 20 USD/MTok (1 hour). 50% off input and output with the Batch API. Anthropic's pricing page states that Mythos 5.1 shares Fable 5.1's specifications and pricing, and lists it as limited availability. |
| Prices checked | Checked | Checked |
| Knowledge cutoff | Unknown | |
| Cutoff checked | Checked | Checked |
- Claude Mythos 5.1: Restricted to trusted access programs and Claude Security; not a generally available API alternative.
Parameters and weights
Unknown: the first-party pages checked publish no parameter count or weights.