The global childList observer scheduled replaceIconsInElement() with no
scope on ANY node insertion — including bare text nodes — so every
notification-bell progress tick during an upload and every
infinite-scroll batch re-scanned the whole document with an attribute
substring selector. Cost grew with total DOM size (5-10k nodes), not
with what was inserted.
Queue the added element roots per animation frame and scan just those
subtrees (an inserted <i> itself is caught via its parent). Text-node
churn no longer triggers any scan at all. The icon replacement is
idempotent, so overlapping roots are harmless.
https://claude.ai/code/session_01Dp3oWon5GBMVn4j3QXZdgx
Claude
8d040314a3