Claude Mythos Preview — EchtRaaW Passport

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Claude Mythos Preview

Anthropic · Language model · Registered 2026-03-29

IDENTITY

Developer

Anthropic

Confirmed by

https://red.anthropic.com/2026/mythos-preview

First registered

2026-03-29 (anthropic_official)

Developer confirmed

2026-04-07

Gate

PROVENANCE COMPLETE

Status

Available · limited release

PROVENANCE

Claimed developer

Anthropic

Confirmed developer

Anthropic

Delta

8 days · match confirmed

EU COMPLIANCE

AI Act

GPAI ⓘ

PASSPORT FIELDS

Model type

Language

Parameters

Undisclosed

Context window

1,000,000 tokens (max output: 128,000 tokens)

Open source

Weights available

License

Proprietary — restricted preview only

Model family

Claude

Superseded by

Claude Mythos 5 Part of lineage

PROVENANCE TIMELINE

2026-06-09

Superseded by Claude Mythos 5

Source: anthropic.com · https://www.anthropic.com/news/claude-fable-5-mythos-5

2026-04-12

First recorded in AI news

Source: reddit_claudeai · https://reddit.com/r/ClaudeAI/comments/1sf4xfr/anthropics_new_mythos_preview_model_is_a_step/

2026-04-08

First recorded in AI news

Source: reddit_claudeai · https://reddit.com/r/ClaudeAI/comments/1sfc54a/claude_mythos_update_and_system_card/

2026-04-07

Benchmarks published: SWE-bench 93.9%, USAMO 97.6%, CyberGym 83.1%

Source: Anthropic system card · https://red.anthropic.com/2026/mythos-preview

2026-04-07

Claude Mythos Preview announced by Anthropic

Source: Anthropic official · https://red.anthropic.com/2026/mythos-preview

2026-04-07

Containment incidents documented during testing

Source: Anthropic system card · https://red.anthropic.com/2026/mythos-preview

2026-04-07

Autonomously discovered CVE-2026-4747 — 17-year-old FreeBSD RCE

Source: Anthropic system card · https://red.anthropic.com/2026/mythos-preview

2026-04-03

First recorded in AI news

Source: reddit_claudeai · https://reddit.com/r/ClaudeAI/comments/1s71oil/new_mythos_model_be_like/

2026-03-29

First recorded in AI news

Source: reddit_singularity · https://reddit.com/r/singularity/comments/1s4t3k7/anthropic_is_testing_mythos_its_most_powerful_ai/

2026-03-29

First recorded in AI news

Source: reddit_artificial · https://reddit.com/r/artificial/comments/1s5hejt/meet_claude_mythos_leaked_anthropic_post_reveals/

2026-03-26

Existence confirmed via CMS data leak

Source: — · https://fortune.com/2026/03/26/anthropic-says-testing-mythos-powerful-new-ai-model-after-data-leak-reveals-its-existence-step-change-in-capabilities/