The write-through was asymmetric. A load applies the inventory row's
height and width to a mount only where they still fit that rack, so a
mount can legitimately be drawn smaller than the row says. A save then
copied the mount's size back onto the row unconditionally — so opening a
rack where a 4U device sits too high, changing anything at all and
saving turned that device into a 1U everywhere, silently. The rack store
did the same in the live session.
Size now travels only when the save actually changed it; an unchanged
size is an echo of the clamp and is dropped. The plate, its colour and
its ports keep going through unconditionally: none of them can overflow
a rail.
The other half of the overlay had no collision check, so a model bigger
than the mount could be applied on top of the neighbour above it —
drawing two plates on the same U, a state the canvas itself refuses and
`RackSaveRequest` happily stored. The overlay now obeys the placement
rule too, and the save endpoint rejects overlapping mounts in one rack
(devices in different racks, and half-width plates side by side on one
U, still pass).
ha-relevant: no
Pouzor
caaa408618