CPython 3.15 JIT Hits 11-12% Performance Goal Over a Year Early on macOS AArch64
simonwillison.net·medium signal
CPython core developer Ken Jin announced the JIT compiler has reached its 'very modest' performance targets more than a year ahead of schedule — 11-12% faster on macOS AArch64 and a few months early on x86_64 Linux as of the 3.15 alpha. This is significant for Python-heavy AI workloads, LLM inference tooling written in pure Python, and the growing ecosystem of AI agent frameworks built on CPython. Simon Willison surfaced the milestone on March 17.