---
title: "Mythos 5.1"
type: entity
entity_type: model
url: https://frontiernewswire.com/models/mythos-5-1
updated: 2026-09-10T10:25:01.000Z
---

# Mythos 5.1

Canonical: https://frontiernewswire.com/models/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)](https://frontiernewswire.com/s/anthropic-gives-eu-cybersecurity-agency-enisa-testing-access-to-mythos-08a1d329) (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)](https://frontiernewswire.com/s/sources-anthropic-declined-to-submit-mythos-5-1-to-the-uk-aisi-for-pre-6dea4387) (Sep 9, 2026)
- [Claude Fable 5.1 made me a really nice animated pelican](https://frontiernewswire.com/s/claude-fable-5-1-made-me-a-really-nice-animated-pelican-v6cb14383) (Sep 1, 2026)
- [Anthropic launches Claude Fable 5.1 and says it’s up to 45 percent cheaper for agentic work](https://frontiernewswire.com/s/anthropic-launches-claude-fable-5-1-and-says-its-up-to-45-percent-v84e4d2c8) (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)](https://frontiernewswire.com/s/claude-fable-5-1-and-mythos-5-1-are-anthropics-first-models-to-e958b312) (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](https://frontiernewswire.com/s/anthropic-releases-claude-fable-5-1-and-claude-mythos-5-1-52-6-on-vfc0348df) (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)](https://frontiernewswire.com/s/anthropic-unveils-claude-fable-5-1-which-is-generally-available-and-cd62eaf9) (Sep 1, 2026)

## Related

- [Anthropic](https://frontiernewswire.com/companies/anthropic) (Company)
- [Claude Fable 5.1](https://frontiernewswire.com/models/claude-fable-5-1) (Model)
- [Fable 5](https://frontiernewswire.com/models/fable-5) (Model)
- [Project Glasswing](https://frontiernewswire.com/topics/project-glasswing) (Topic)
- [AWS](https://frontiernewswire.com/companies/aws) (Company)
- [GPT-5.6 Sol](https://frontiernewswire.com/models/gpt-5-6-sol) (Model)
- [Mythos 5](https://frontiernewswire.com/models/mythos-5) (Model)
- [Claude Opus 5](https://frontiernewswire.com/models/claude-opus-5) (Model)

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