Update on the CPython JIT: What to expect in 3.15

This talk is a follow-up to my EuroPython 2025 session on the foundations of the CPython JIT compiler. It looks at how the JIT has evolved since Python 3.14 and where it stands as Python 3.15 approaches release. We cover the transition of the JIT from an experimental feature towards a supported part of CPython, how it fits into the runtime today, and what that means in practice for users and distributors. The talk also explores how the JIT interacts with free-threaded builds, the current status of integration with external debuggers, and how these constraints shape real-world usage. Finally, we examine how the JIT performs today, where it already delivers substantial speedups, where it does not, and what realistic performance expectations look like for Python 3.15.