Mythos 5.1
#120 in Frontier LLMsUnknown · v5.1 · since September 1, 2026 · 3× · last seen Oct 18, 2026
19
Momentum
Claude Mythos 5.1 is a frontier large language model from Anthropic, released on September 1, 2026. It uses the same model weights as Claude Fable 5.1 but with more permissive safeguards, and is available only to verified organizations through trusted access programs. Official pricing matches Fable 5.1.
Momentum trend
21.07.19.10.
Features
| Context Window (Tokens) | 1M tokens input, max. 128K tokens output |
| License | Proprietary (usage under provider terms) |
| Multimodality | Input: text and images; output: text |
| Platform | Claude API, Amazon Bedrock, Google Cloud, Microsoft Foundry (verified organizations only) |
| Price per 1M Tokens | Input $10 / Output $50 (cache read $0.25, batch 50% discount) |
| Release Date | September 1, 2026 |