The Python Software Foundation has expedited the release of Python 3.14.0rc2, the penultimate release candidate for the 3.14 series, following a critical bug fix that forced an unscheduled update to the bytecode magic number. This early release shifts the next preview to a third release candidate (rc3), with no change to the final release date of October 7, 2025.

“We fixed a bug that required bumping the magic number stored in Python bytecode files,” a Python release manager explained. “This means .pyc files created for rc1 cannot be used with rc2 and will be recompiled, but the ABI remains unchanged—wheels built for rc1 will work seamlessly with rc2, rc3, and the final 3.14.x series.”

The original schedule planned rc2 for August 26, but the fix prompted an early rollout. As a result, an additional release candidate (rc3) is now scheduled for September 16, 2025. The release manager added, “This early release lets us add a third release candidate without impacting the final date, giving the community more time to test.”

Background

Python 3.14 has entered its release candidate phase, meaning only verified bug fixes are allowed moving forward. The 3.14 series introduces several landmark features:

• PEP 779: Free-threaded Python is now officially supported.
• PEP 649: Annotation evaluation is deferred, improving semantics.
• PEP 750: Template string literals (t-strings) for custom processing.
• PEP 734: Multiple interpreters in the standard library.
• PEP 784: New compression.zstd module for Zstandard.
• PEP 758: Optional brackets in except and except* expressions.
• Syntax highlighting in PyREPL, plus color support in unittest, argparse, json, and calendar CLIs.
• PEP 768: Zero-overhead external debugger interface for CPython.
• UUID versions 6–8 are now supported, and v3–5 generation is up to 40% faster.

Additionally, Python 3.13.7 has been released as a maintenance update for the 3.13 line, addressing stability improvements. No further details were provided.

What This Means

For third-party project maintainers, this is the last call to test compatibility with Python 3.14. The release team urges developers to publish Python 3.14 wheels on PyPI now. “Binary wheels built against any 3.14 release candidate will work with future versions, so start testing immediately,” the team stated in a call to action.

The addition of a third release candidate provides a broader testing window without delaying the final release. With no ABI changes expected from this point, all wheels and extensions should remain compatible.

Core developers are reminded to finalize documentation: update “What’s New” entries and ensure all changes are properly recorded. The final 3.14.0 release remains on track for October 7, 2025. Please report any issues to the Python bug tracker.

Use of this preview release in production environments is not recommended.