From 8cb12b95a943fb58f3be4e7b895e3b15c99e119d Mon Sep 17 00:00:00 2001
From: gsxdsm <gsxdsm@users.noreply.github.com>
Date: Wed, 22 Jul 2026 15:16:02 -0700
Subject: [PATCH] fix(dashboard): stop mobile board jump on tap during momentum

Re-touch while the board is coasting now cancels the pending directional settle and re-baselines the gesture at the current scrollLeft, so a stop-tap no longer hard-jumps using the original swipe.
---
 .../__tests__/useColumnScrollSnap.test.ts     | 57 +++++++++++++++++++
 .../app/hooks/useColumnScrollSnap.ts          | 28 +++++++++
 2 files changed, 85 insertions(+)

diff --git a/packages/dashboard/app/hooks/__tests__/useColumnScrollSnap.test.ts b/packages/dashboard/app/hooks/__tests__/useColumnScrollSnap.test.ts
index cd531d998f..f05a088bde 100644
--- a/packages/dashboard/app/hooks/__tests__/useColumnScrollSnap.test.ts
+++ b/packages/dashboard/app/hooks/__tests__/useColumnScrollSnap.test.ts
@@ -343,6 +343,63 @@ describe("useColumnScrollSnap", () => {
     expect(scroller.scrollLeft).toBe(0);
   });
 
+  /*
+  FNXC:BoardNavigation 2026-07-22-15:10:
+  Tap-to-stop during post-lift momentum must not hard-jump using the original swipe direction.
+  */
+  it("does not jump when the user taps during momentum after a swipe", () => {
+    const scroller = createScroller(3, 0);
+    renderHook(() => useColumnScrollSnap(scroller, { mobileOnly: true, isUserInteraction: () => true }));
+
+    act(() => {
+      // Start a forward swipe and lift so the idle settle is armed.
+      dispatchPointerEvent(scroller, "pointerdown", 200);
+      dispatchPointerEvent(scroller, "pointermove", 160);
+      scroller.scrollLeft = 30;
+      scroller.dispatchEvent(new Event("scroll"));
+      dispatchPointerEvent(scroller, "pointerup", 160);
+
+      // Coast a bit more (native fling), then the user taps to stop mid-travel.
+      scroller.scrollLeft = 55;
+      scroller.dispatchEvent(new Event("scroll"));
+      dispatchPointerEvent(scroller, "pointerdown", 100);
+      dispatchPointerEvent(scroller, "pointerup", 100);
+    });
+
+    // Without re-baselining the second touch, the original rightward settle would jump to COLUMN_WIDTH.
+    settleAfterMomentum();
+    act(() => {
+      vi.advanceTimersByTime(500);
+    });
+
+    expect(scroller.scrollLeft).toBe(55);
+  });
+
+  it("starts a new directional settle after a pan that continues from a mid-momentum re-touch", () => {
+    const scroller = createScroller(3, 0);
+    renderHook(() => useColumnScrollSnap(scroller, { mobileOnly: true, isUserInteraction: () => true }));
+
+    act(() => {
+      dispatchPointerEvent(scroller, "pointerdown", 200);
+      dispatchPointerEvent(scroller, "pointermove", 160);
+      scroller.scrollLeft = 30;
+      scroller.dispatchEvent(new Event("scroll"));
+      dispatchPointerEvent(scroller, "pointerup", 160);
+
+      // Interrupt fling, then pan back left so settle must use the new gesture only.
+      scroller.scrollLeft = 55;
+      scroller.dispatchEvent(new Event("scroll"));
+      dispatchPointerEvent(scroller, "pointerdown", 100);
+      dispatchPointerEvent(scroller, "pointermove", 140);
+      scroller.scrollLeft = 20;
+      scroller.dispatchEvent(new Event("scroll"));
+      dispatchPointerEvent(scroller, "pointerup", 140);
+    });
+    settleAfterMomentum();
+
+    expect(scroller.scrollLeft).toBe(0);
+  });
+
   it("does not attach on non-phone desktop", () => {
     stubViewport("wide-short-desktop");
     expect(isMobileViewport()).toBe(false);
diff --git a/packages/dashboard/app/hooks/useColumnScrollSnap.ts b/packages/dashboard/app/hooks/useColumnScrollSnap.ts
index e74c58cff9..ae6f2d4b5f 100644
--- a/packages/dashboard/app/hooks/useColumnScrollSnap.ts
+++ b/packages/dashboard/app/hooks/useColumnScrollSnap.ts
@@ -8,6 +8,11 @@ rubber-band/fling end often reverses for a frame — and (2) origin±nearest hyb
 Direction is locked at finger-up from net gesture delta only (never post-lift ticks). Target
 is always the next column in that scroll direction from the current viewport (classic
 directional page snap). Pin until next touch; hard-jump kills residual fling.
+
+FNXC:BoardNavigation 2026-07-22-15:10:
+A tap during post-lift momentum must cancel the pending directional settle and re-baseline
+the gesture at the current scrollLeft (pointerHeld true). Otherwise the original swipe's
+idle timer still hard-jumps the board away from where the user stopped.
 */
 /** After lift/cancel/wheel: wait for scroll idle (momentum finished) before paging. */
 const SCROLL_IDLE_SETTLE_MS = 48;
@@ -389,12 +394,35 @@ export function useColumnScrollSnap(
       idleTimer = setTimeout(snapInScrollDirection, SCROLL_IDLE_SETTLE_MS);
     };
 
+    /*
+    FNXC:BoardNavigation 2026-07-22-15:10:
+    A second touch during post-lift momentum must cancel the pending directional settle and start a fresh gesture at the current scrollLeft.
+    Previously, re-touch while interactionActive only re-captured the pointer and returned early — pointerHeld stayed false, the idle timer kept the original swipe direction, and the board hard-jumped away from where the user tapped to stop.
+    */
     const beginInteraction = (event: Event) => {
       if (!isUserInteraction(event)) return;
 
       clearPin();
 
+      // Mid-momentum re-touch (or duplicate pointerdown+touchstart): cancel pending snap and re-baseline.
       if (interactionActive) {
+        clearIdleTimer();
+        lockedDirection = 0;
+        sawHorizontalMovement = false;
+        gestureStartScrollLeft = scroller.scrollLeft;
+        lastScrollLeft = scroller.scrollLeft;
+        const clientX = getClientX(event);
+        gestureStartClientX = clientX;
+        lastClientX = clientX;
+
+        if (event.type === "wheel") {
+          pointerHeld = false;
+          suspendNativeSnap();
+          armIdleSettle();
+          return;
+        }
+
+        pointerHeld = true;
         if (event.type === "pointerdown" && "pointerId" in event) {
           try {
             scroller.setPointerCapture((event as PointerEvent).pointerId);