probe-fiber-tree.mts walks the live React tree and reports which components are
mounted, what DOM they render and their props. Heap snapshots only give minified
names like `y`, and source maps do not help because the snapshot records runtime
names — props shape plus rendered DOM identifies a component reliably. It injects
a DevTools hook stub before load so React registers every root; climbing from one
DOM node's fiber missed most of the tree (2,093 fibers vs 3,918).
What it found, on a 28-widget board:
- The most-mounted component is @mantine/core/Box (513). It is the primitive every
Mantine component renders through, so it is a symptom of how much is mounted
rather than a bug. Proportions match the 650 MB session snapshot (13% vs 17%),
so the minified `y` there is almost certainly Box.
- 71 Menu -> Popover -> PopoverDropdown triplets are mounted for context menus that
are almost never opened. Isolated with the existing enableRightClickOnWidgets
flag: 3,918 fibers with them, 3,554 without — 364 fibers, 9%, scaling with item
count. The dropdown contents are already lazy; the wrappers are not.
A fix that deferred the Menu until first right-click was reverted: it broke
right-click and inflated the tree to 20,107 fibers, because the replayed
contextmenu event re-entered the arming handler. Doing it properly needs one
board-level menu instead of one per item. The Playwright check that caught this is
in the findings — a fiber count alone would have read as a win.
Also records that the demo account had completed_board_tour = 0, so earlier rounds
measured the first-time-user path; completing it moves the tree by 38 fibers, so
the published numbers stand.
Thomas Camlong
fd7bcb2231