In 3.14, type annotations are not evaluated eagerly.

https://docs.python.org/3.14/whatsnew/3.14.html#whatsnew314-pep649

So this snippet runs fine:

class X:
    x: X

Ruff flags the field annotation as an undefined name. It is undefined in 3.13 and earlier, but in 3.14 this is a false positive. Earlier versions require from __future__ import annotations to make this work.