The guard polled for `scrollHeight > clientHeight + 40` and the next
line asserted the container could be scrolled to 80, so any range in
41-79 satisfied the precondition and could not satisfy the assertion.
The grid passes through exactly that while it settles, because it
recomputes its columns after a viewport change rather than during it,
so the test read a clamped scrollTop and reported 10 against 80.
It failed CI on a pull request that changes one paragraph of CLAUDE.md
and nothing else, while WebKit passed in the same run. Reproduced
locally: 0 failures in 6 runs before #132, 2 in 9 after, 0 in 10 with
this change.
#132 is what made it reachable rather than what broke it. The queue
panel's mode is measured rather than media-queried, so a viewport
change at this width costs one more layout pass, and cover-grid settles
after it instead of before. The settled range is 330 and stable, the
main panel is 700px, and the panel is correctly display:none while
closed — there is no user-visible defect, only a wider window for a
race the spec already had.
A threshold below the value its caller depends on is not a guard, so
the target is one constant that both the guard and the assertion read.
Closes#133
logan