A selection change re-ran every CardFaceView on the board (180 bodies ≈ 85 ms on
the 6×30 fixture, 515 ≈ 233 ms on a real 515-card board, debug): the face's body
read store.selection in three places — isSelected, the drag replica's count, and
the context menu's styleTarget — and Observation invalidates every reader of the
property, past the equatable gate entirely. The band overlay stayed cheap, which
is why the marquee tracked the cursor while the highlight lagged ~0.4 s behind.
Now LaneView and TrashLaneView hoist one selection read per body and hand each
face isSelected/selectedCount as compared parameters; StyleMenuItems takes its
target as a deferred closure; TrashLaneRowView gains the same treatment plus the
Equatable gate it never needed before. Select-one-card: 180 bodies → 1. A
growing band costs the selection's own running size; the real board's crossing
fell 233 → 112 ms — the remainder is lane bodies re-measuring their masonry, a
separate lane-level finding recorded in RENDER-INSTRUMENTATION.md.
Also: select() gains defaultsSoleMember — the marquee's explicit nils never
avoided the sole-member default, so a one-card band acquired a selectionHead and
could scroll the lane out from under its own drag.
MarqueeRenderCostTests pins the shape: redundant samples cost zero bodies, a
growing band pays per crossing, and selectionStillRepaints holds a ≤8 budget.
Measured on real events 2026-08-07, correcting the 2026-08-06 hosted
finding: a bare count-1 tap on LaneView's empty-space layer fires in
~1-3 ms with no drag source at all — the hold that made the empty
.onDrag look necessary was the sterile NSApp.postEvent stream
over-disambiguating. And the provider was actively harmful: even an
empty drag source claims the mouse-drag at threshold, starving the
marquee's simultaneous DragGesture after one sample — the band froze
and the mouseUp never arrived. The layer goes dragless; drags from
empty space belong wholly to MarqueeControl. PointerClick's and the
layer's comments retell the corrected story. Alongside: openCard is
typed @MainActor throughout, which makes the closure Sendable and
lets CardFaceRole carry it under CardFaceView's nonisolated ==.
Claude-Session: https://claude.ai/code/session_014PtZdPwqZuqEDLc6wZMtEy
LaneView and CardFaceView become Equatable and are instantiated through
.equatable(): the strip's body re-runs on every drop-proposal change, and
without the gates that rebuilt every lane and every card face on every
cursor move of a drag. The == compares value inputs and window-lived
collaborator identities; the closures BoardView rebuilds each pass are
deliberately excluded (BoardDropContext.isEquivalent / MarqueeControl.
isEquivalent / CardFaceRole.isEquivalent own that judgment). Observation
reads inside the bodies still self-invalidate — the lane under the drag
keeps re-running; the other lanes stop.
Ports the pathfinder's CardView/ColumnView gating pattern (drag-perf
suspect #2, card cbb6e476).
Claude-Session: https://claude.ai/code/session_01CqjXB7ASoWtbyoGod68k97
rzen