[zahlman]

pyproject.toml is still fundamentally intended to be an input file that describes abstract dependencies for a single package. Lock files describe entire environments, or at least entire change-sets for an environment, and specify everything - pinned versions, including for transitive dependencies, and also hashes and other expectations for the install artifacts.

Tools that use custom lock files are at liberty to switch over, and any concerns about migration, backwards compatibility etc. are up to them. Several major tool authors were consulted for the design repeatedly across the discussion thread, over a period of months (and this is just the latest attempt at the design task; the total history is much longer).

uv has an issue up already to track implementation: https://github.com/astral-sh/uv/issues/12584