Python 3.15.0rc1 shipped on August 4, 2026, with the final release scheduled for October 1, 2026 and no further ABI changes in the 3.15 series.
PEP 803 gives free-threaded builds a stable ABI, so C extension authors can ship binary wheels that keep working across 3.15 point releases.
Free-threaded CPython still costs 1% to 8% in single-threaded performance and more memory, and it remains a separate opt-in build rather than the default.