How blanket gives Python tests deterministic control over thread scheduling, and why that matters now that free-threaded Python is shipping.

At PyCon US 2026 🐍 one of the standout talks for me was Larry Hastings on testing multithreaded code 🧵 via blanket. Dug deeper into the topic afterwards and wrote it up. Free-threaded Python is around the corner ⚡ so will become ever more important. Comments