Toolchain policy

Python 3.11 is the floor (python = ">=3.11,<4.0" in pyproject.toml), with CI on 3.11, 3.12, 3.13 and 3.14 on Linux, macOS and Windows. Raising the floor is a maintainer decision, recorded in the changelog, and moves with the rest of the camt053 suite in the same release. No distro-system Python is supported.

Runtime dependencies carry upper bounds, except certifi, which is calendar-versioned and has to stay current. A dependency with a published advisory, direct or transitive, is floored in pyproject.toml so no affected version can resolve (for example anyio>=4.14.2, starlette>=1.3.1, cryptography>=50.0.0); tests/test_advisory_floors.py holds each floor. The CI and release tooling installs from hash-pinned requirements/*.txt, regenerated with make pip-compile.