graph-stale
An advisory: it explains, and blocks nothing, on a graph read while the index is older than the sources it describes.
What it catches
A graph read while the index is older than the sources it describes.
Seeing it
A verdict names its rule in brackets, which is how you got here:
advise [graph-stale]: ...
magus describe rule graph-stale prints the same entry at a terminal, and
magus describe rules lists every rule this workspace enforces.