Python 3.14

Python 3.14 adds deferred evaluation of annotations through a new annotation evaluation model and the annotationlib module, changing when annotation expressions run and how tools should inspect them. It adds template string literals, which preserve the expression and value components of an interpolated string for programmatic processing. The standard library gains support for creating and coordinating multiple interpreters, plus native Zstandard compression support. Free-threaded CPython is now a supported build mode, while the conventional build continues to use the global interpreter lock by default. CPython also includes an experimental just-in-time compiler; it is not a portability or performance assumption applications should make. The release contains further language, standard-library, typing, and C-API changes, so code that relies on implementation details, annotation side effects, or compiled extensions needs upgrade testing rather than a version-number-only rollout.

Python 3.14 remains within its active support window, so staying on it does not create an immediate lifecycle-driven migration requirement. The main cost is falling behind later CPython bug fixes, security fixes, platform support changes, performance work, and library compatibility once dependencies begin requiring a newer interpreter. Teams that use the free-threaded build face an additional compatibility risk: extensions must be explicitly prepared for free-threading, and behavior can differ from the default GIL-enabled build. Remaining on 3.14 also means that future application and dependency changes may accumulate into a larger upgrade, particularly where type annotations, C extensions, or interpreter-specific behavior are involved.

Standardize on the latest maintained 3.14 patch release and keep it current through the normal maintenance process. Run the full test suite, dependency resolution, packaging build, and deployment smoke tests on 3.14 across every supported operating system and architecture. Audit code and tools that read __annotations__ directly, especially if annotations can execute imports or other side effects; use the supported annotation-evaluation APIs where appropriate. Rebuild and test every native extension against 3.14, including third-party wheels and internal C, Cython, Rust, or other compiled bindings. Treat free-threaded execution and the experimental JIT as separate opt-in test configurations, not as default production assumptions. Add the next CPython feature line to continuous integration early, resolve dependency constraints there, and record any reliance on deprecated APIs or CPython implementation details before those issues become release-blocking.