# Mythos: what I've logged

> Mythos comes up in 2 posts of my AI log, from April 2026 to August 2026, and each item below links to the primary source. The sources come from Anthropic, filed under frontier, open weights and science.

## Items

1. **Claude Fable 5.1 and Claude Mythos 5.1** (Anthropic, 31 Aug 2026): One underlying model at two safeguard levels, with cache reads 75% cheaper and base prices unchanged at $10 in and $50 out per million tokens. [Primary source](https://www.anthropic.com/claude-fable-and-mythos-5-1) · [Post](https://heyaliasif.com/ai/2026-08-31-week-in-ai#item-1)
2. **Project Glasswing and Claude Mythos Preview** (Anthropic, 6 Apr 2026): A frontier model held back from general release and given to defenders first, backed by up to $100M in usage credits and $4M for open-source security groups. [Primary source](https://www.anthropic.com/glasswing) · [Post](https://heyaliasif.com/ai/2026-04-06-week-in-ai#item-1)

## Posts

- 2026-08-31 [Claude Fable 5.1 and GPT-6 Astra both land, plus Gemini 3.8 Flash](https://heyaliasif.com/ai/2026-08-31-week-in-ai)
- 2026-04-06 [Anthropic gates Mythos Preview, Meta's Muse Spark, GLM-5.1](https://heyaliasif.com/ai/2026-04-06-week-in-ai)

Canonical: https://heyaliasif.com/ai/topics/mythos