mypy is being deprecated in favor of ty, which provides significantly faster type checking with better performance characteristics and more accurate type inference. ⚡

The migration replaces mypy==1.19.1 with ty==0.0.16 in the type checking tox environment. The command changes from running mypy separately on src and tests to a single ty check invocation with concise output format and warnings treated as errors.

Configured ty to target Python 3.14 specifically to align with the type checking environment and avoid false positives from conditional imports like tomli that only apply to older Python versions. 🐍