Claude Fable 5.2 built an operating system. Here's what else is new

Claude Fable 5.2 is out. Here's what's new, from Anthropic's announcement of November 9, 2026. - One Anthropic engineer gave it an empty folder. Eight days and over 1,000 subagents later, it had an operating system that boots on a laptop. - Fable 5.2 and Mythos 5.2 are the same underlying model. Fable has strong cybersecurity and biology safeguards, so it's open to everyone. Mythos goes to vetted organizations. - Up to 30% faster than Fable 5.1, and cheaper: $8 per million input tokens, $40 per million output. An optional fast mode is up to 2.5 times faster, for twice the price. - FrontierCode: on High effort it scored about the same as Opus 5.5 at its best (45.3% vs 45.5%), at roughly half the cost per task. On Xhigh it reached 49.1%, the highest of any released model Anthropic tested. - Before launch: three working electronic devices from a one-paragraph prompt, real robots, two open problems in physics, and Fermat's Last Theorem formalized by 1,000 agents in 30 hours. - About 55% fewer blocks than Fable 5.1. A blocked request is answered by Opus 4.8 for cybersecurity, or Opus 5 for biology. - Anthropic's advice: start with Opus 5.5 for most coding and knowledge work, move up to Fable for the most ambitious work, or down to Sonnet or Haiku. Chapters 0:00 Fable 5.2 built an OS 0:14 Two names, one model 0:30 Faster and cheaper 0:53 Benchmarks 1:10 Before launch 1:31 Fewer refusals 1:46 When to use it 2:01 Where to get it 2:11 My take Source: Anthropic, Claude Fable 5.2 and Claude Mythos 5.2 https://www.anthropic.com/claude-fable-and-mythos-5-2 Charts, videos and quoted text in this video: anthropic.com.