TeX .fmt Caching Lacks Automatic Stale‑File Detection

Goal: Configure the TeX engine so that a format file (.fmt) is automatically considered stale and rebuilt whenever any of its source .tex or .sty files are modified.

Constraint: The current caching mechanism does not track file timestamps or content changes of the inputs, and there is no way to declare a set of directories that should trigger regeneration without manual commands like texhash or fmtutil.

Question: Can the TeX engines be extended to monitor the modification times of dependent files and rebuild the format automatically?

Question: Is there a configuration option to specify which directories or file patterns should cause automatic format invalidation?

Question: What mechanisms could be added to warn users when a stale .fmt is being used?