Glimmer Index
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Claude Mythos 5

Anthropic · Released Jun 9, 2026 · Closed weights

Restricted Claude model for advanced cybersecurity and biology research workflows

Context window
1M
tokens in · 128K out
Lab announcement ↗Open in the timeline

The Claude Mythos line

2 releases in the Claude Mythos line.

Claude Mythos 5Jun 9, 202684dClaude Mythos 5.1Sep 1, 2026

A newer release is out: Claude Mythos 5.1.

BENCHMARKS

Not in the Epoch Capabilities Index. Epoch benchmarks what it can run, so this is a gap in coverage, not a poor result.

Anthropic's past year

12 release days in the past year, about one every 30 days. The next is expected around Nov 10, 2026. Forecasts ↗

NovDecJanFebMarAprMayJunJulAugSepOctNov

Specifications

RELEASE DATEJun 9, 2026
WEIGHTSClosed weights
CONTEXT WINDOW1M
MAX OUTPUT128K
REASONINGNot listed
TOOL CALLINGNot listed
INPUTStext, image/jpeg, image/png, image/gif, image/webp, application/pdf
OUTPUTStext

Models.dev record ↗

Specifications and prices from Models.dev; availability and limits may differ by provider. Benchmarks from Epoch AI (CC BY 4.0), LiveBench and the other sources named above.