Mythos 5.1
- TYPE
- Model
- SIGNALS
- 7
- FIRST SEEN
- Sep 1, 2026
- LAST SEEN
- Sep 10, 2026
Recent signals
- Anthropic gives EU cybersecurity agency ENISA testing access to Mythos 5 after months of talks that began in late May; ENISA still lacks access to Mythos 5.1 (Gian Volpicelli/Bloomberg) Sep 10, 2026
- Sources: Anthropic declined to submit Mythos 5.1 to the UK AISI for pre-release testing, prompting UK fears that US AI labs are aligning with US protectionism (Financial Times) Sep 9, 2026
- Claude Fable 5.1 made me a really nice animated pelican Sep 1, 2026
- Anthropic launches Claude Fable 5.1 and says it’s up to 45 percent cheaper for agentic work Sep 1, 2026
- Claude Fable 5.1 and Mythos 5.1 are Anthropic's first models to watermark text outputs; a detection API is available to eligible groups as required under EU law (Ben Patterson/PCWorld) Sep 1, 2026
- Anthropic Releases Claude Fable 5.1 and Claude Mythos 5.1: 52.6% on Terminal-Bench-Science and 75% Cheaper Cache Reads Sep 1, 2026
- Anthropic unveils Claude Fable 5.1, which is generally available, and Mythos 5.1, for trusted partners and with cybersecurity and life sciences safeguards (Anthropic) Sep 1, 2026