Fable 5.1 Ships — And Breaks Your Tool Calls | 02 Sep 26

Anthropic launched Claude Fable 5.1 and Mythos 5.1 with a 1M context window, cache reads at a quarter of the old price, and three breaking changes — forced tool use now returns a 400, thinking blocks are bound to your conversation history, and every word carries a statistical watermark. Alex explains what `tool_choice` actually does, why always-on thinking makes forced tool calls a bad idea, and how statistical text watermarking works without hiding a single character. Plus IBM's Granite 4.2 reasoning models land under Apache 2.0 with a thinking switch. Hosts: Alex & Jules. New episodes daily.