Python's experimental JIT compiler axed
Original: Python's experimental JIT to be removed
Why This Matters
JIT removal signals Python's governance is tightening standards for major runtime features.
CPython's experimental JIT compiler, added in Python 3.13 in 2024, is being removed after its maintainers withdrew PEP 836, the proposal needed to keep it in the codebase past a steering council deadline.
Python's steering council gave JIT maintainers a six-month ultimatum in June: submit and get PEP 836 accepted, or the JIT gets pulled from CPython's main branch. The maintainers have now withdrawn the PEP, effectively ending the project. The JIT was originally merged by Brandt Bucher in early 2024 without a formal standards-track PEP — an unusual move for a feature of that scale. An informational PEP 744 was drafted after the fact, but the council eventually required something with real teeth: defined guarantees, maintenance commitments, and clear impact on redistributors. Thomas Wouters cited no single trigger for the council's intervention, but pointed to a cluster of concerns: conflicts with instrumentation, debugging, and profiling work, plus friction with external JIT projects like CinderX and compile tools like Numba and PyTorch. PEP 836, titled "JIT Go Brrr," was published for community feedback on July 3 and drew substantial discussion — but critics, including Wouters and Mark Shannon, felt the draft didn't adequately answer the council's core questions. With the PEP now withdrawn, CPython loses its only built-in JIT path, at least for now.