fix(mobile-tabs-pager): restore segment-button taps in pager mode via opacity-0 per-pane row and route their commits through an instant no-transition strip jump

src/app/components/mobile-tabs-pager/MobilePagerPaneContext.tsx

@@ -1,19 +1,31 @@
 import { createContext, useContext } from 'react';
 
+export type MobilePagerTab = 'direct' | 'channels' | 'bots';
+
 // Set by MobileTabsPager around each of its three listing panes. Lets
 // the StreamHeader inside the pane discover (a) that it's mounted in
-// pager mode at all, and (b) whether it's the currently active pane.
+// pager mode at all, (b) whether it's the currently active pane, and
+// (c) how to request a tab switch with no animation (used by the
+// invisible per-pane Segment buttons that capture taps in the safe-
+// top + tabsRow band — see `StreamHeader.tsx` for why the row is
+// `opacity:0` instead of `visibility:hidden`).
 //
 // "Mounted in pager mode" controls whether the per-pane tabs row
-// renders visibly — when we're in pager mode the tabs row is hidden
-// via visibility:hidden (the shared static header at pager root paints
-// the visible tabs + icons), but the row still occupies its
-// TABS_ROW_PX height so the curtain's snap geometry is unchanged.
+// renders visibly — when we're in pager mode the tabs row is painted
+// invisible (the shared static header at pager root paints the visible
+// tabs + icons), but the row still occupies its TABS_ROW_PX height so
+// the curtain's snap geometry is unchanged.
 //
 // "isActive" controls which pane's curtain is wired to the shared
 // static header's action icons via `mobilePagerCurtainAtom`.
+//
+// `selectTabInstant` is the tap commit path. It snaps the strip to
+// the target tab without the swipe-finish CSS transition — taps feel
+// snappy where swipes still animate. Swipes still go through the
+// pager's gesture hook which uses a separate animated commit.
 export type MobilePagerPaneInfo = {
   isActive: boolean;
+  selectTabInstant: (target: MobilePagerTab) => void;
 };
 
 const MobilePagerPaneContext = createContext<MobilePagerPaneInfo | null>(null);

src/app/components/mobile-tabs-pager/MobileTabsPager.tsx

@@ -20,13 +20,16 @@ import { Bots } from '../../pages/client/bots';
 import { ChannelsModeProvider } from '../../hooks/useChannelsMode';
 import { settingsSheetAtom } from '../../state/settingsSheet';
 import { channelsWorkspaceSheetAtom } from '../../state/channelsWorkspaceSheet';
-import { MobilePagerPaneProvider } from './MobilePagerPaneContext';
+import { MobilePagerPaneProvider, MobilePagerTab } from './MobilePagerPaneContext';
 import { MobileTabsPagerHeader } from './MobileTabsPagerHeader';
 import { useMobileTabsPagerGesture } from './useMobileTabsPagerGesture';
 import { PAGER_EASING, PAGER_TRANSITION_MS, PANE_GAP_PX } from './geometry';
 import * as css from './style.css';
 
-type Tab = 'direct' | 'channels' | 'bots';
+// Aliased to the context's `MobilePagerTab` so the per-pane Segment's
+// `selectTabInstant(target)` callback (exposed via MobilePagerPaneInfo)
+// stays type-aligned with the pager's own `tabs` array.
+type Tab = MobilePagerTab;
 
 // URL-safe wrapper around decodeURIComponent — matches the same helper
 // inside `useActiveSpace`. Used here to validate the URL `:spaceIdOrAlias`
@@ -180,6 +183,12 @@ export function MobileTabsPager() {
 
   const [dragPx, setDragPxState] = useState(0);
   const [dragging, setDraggingState] = useState(false);
+  // Tap-driven commits set this for one frame to suppress the strip's
+  // CSS transform transition. The strip jumps to the new tab without
+  // the 280ms slide animation that swipe commits intentionally play.
+  // Cleared in a rAF effect below so subsequent state changes resume
+  // with normal transitions.
+  const [instantSwitch, setInstantSwitch] = useState(false);
   // Stored as a Tab NAME, not an index. The `tabs` array's length and
   // composition can change at runtime (showBots flipping when the user
   // navigates onto/off /bots/, or when a bot-config refresh adds a
@@ -221,30 +230,56 @@ export function MobileTabsPager() {
     [mx, activeSpaceId]
   );
 
-  const commitTo = useCallback(
-    (idx: number) => {
+  // Shared commit core. `instant=true` flips `instantSwitch` for one
+  // frame so the strip's transform jump from old tab to new lands
+  // without the swipe-finish CSS transition — used by tap paths
+  // (static header Segments + per-pane Segments). `instant=false`
+  // preserves the animation — used by the swipe gesture commit so
+  // the strip smoothly completes the user's drag.
+  const commitToInternal = useCallback(
+    (idx: number, instant: boolean) => {
       const target = tabs[idx];
       if (!target) return;
       setDragPxState(0);
       setDraggingState(false);
+      if (instant) setInstantSwitch(true);
       setPendingTargetTab(target);
       navigate(destinationFor(target), { replace: true });
     },
     [tabs, navigate, destinationFor]
   );
 
-  const onSelectDirect = useCallback(() => {
-    const i = tabs.indexOf('direct');
-    if (i >= 0) commitTo(i);
-  }, [tabs, commitTo]);
-  const onSelectChannels = useCallback(() => {
-    const i = tabs.indexOf('channels');
-    if (i >= 0) commitTo(i);
-  }, [tabs, commitTo]);
-  const onSelectBots = useCallback(() => {
-    const i = tabs.indexOf('bots');
-    if (i >= 0) commitTo(i);
-  }, [tabs, commitTo]);
+  const commitToSwipe = useCallback(
+    (idx: number) => commitToInternal(idx, false),
+    [commitToInternal]
+  );
+
+  // Tap entry by tab name. Exposed to per-pane Segments via
+  // `MobilePagerPaneInfo.selectTabInstant` so the invisible per-pane
+  // segment buttons (which capture taps when the static header isn't
+  // z-elevated) route through the same instant commit path as the
+  // static header's own segment buttons.
+  const selectTabInstant = useCallback(
+    (target: Tab) => {
+      const i = tabs.indexOf(target);
+      if (i >= 0) commitToInternal(i, true);
+    },
+    [tabs, commitToInternal]
+  );
+
+  const onSelectDirect = useCallback(() => selectTabInstant('direct'), [selectTabInstant]);
+  const onSelectChannels = useCallback(() => selectTabInstant('channels'), [selectTabInstant]);
+  const onSelectBots = useCallback(() => selectTabInstant('bots'), [selectTabInstant]);
+
+  // Clear `instantSwitch` on the next paint frame so subsequent
+  // transform changes use the normal animated transition again. rAF
+  // (not setTimeout 0) so we cancel cleanly if a new commit re-arms
+  // the flag before the frame fires.
+  useEffect(() => {
+    if (!instantSwitch) return undefined;
+    const id = requestAnimationFrame(() => setInstantSwitch(false));
+    return () => cancelAnimationFrame(id);
+  }, [instantSwitch]);
 
   const pendingTargetIdx = pendingTargetTab !== null ? tabs.indexOf(pendingTargetTab) : -1;
 
@@ -292,7 +327,12 @@ export function MobileTabsPager() {
     tabsCount: tabs.length,
     disabled: gestureDisabled,
     setDragPx,
-    commitTo,
+    // Swipe commits keep the slide animation — the strip glides from
+    // the drag-released position to the target tab. Tap commits use
+    // `selectTabInstant` (passed down via per-pane context + the
+    // static header's `onSelectXxx` props) which sets `instantSwitch`
+    // for one frame to skip the transition.
+    commitTo: commitToSwipe,
   });
 
   // Gap-aware strip transform. Each adjacent pane is offset by an
@@ -307,10 +347,16 @@ export function MobileTabsPager() {
       transform: `translate3d(calc(${-visualIdx * 100}vw - ${
         visualIdx * PANE_GAP_PX
       }px + ${visualDragPx}px), 0, 0)`,
-      transition: dragging ? 'none' : `transform ${PAGER_TRANSITION_MS}ms ${PAGER_EASING}`,
+      // Transition suppressed while a finger drag is in flight (the
+      // strip follows the finger 1:1) AND for the single frame after
+      // a tap-driven commit (`instantSwitch`) so segment taps snap to
+      // the target tab without the 280ms slide. Swipe commits leave
+      // `instantSwitch` false so the slide-to-target animation plays.
+      transition:
+        dragging || instantSwitch ? 'none' : `transform ${PAGER_TRANSITION_MS}ms ${PAGER_EASING}`,
       gap: `${PANE_GAP_PX}px`,
     }),
-    [tabs.length, visualIdx, visualDragPx, dragging]
+    [tabs.length, visualIdx, visualDragPx, dragging, instantSwitch]
   );
 
   // Per-pane context values memoised separately so each pane's
@@ -323,16 +369,16 @@ export function MobileTabsPager() {
   const channelsIdx = useMemo(() => tabs.indexOf('channels'), [tabs]);
   const botsIdx = useMemo(() => tabs.indexOf('bots'), [tabs]);
   const directPaneInfo = useMemo(
-    () => ({ isActive: urlActiveIdx === directIdx }),
-    [urlActiveIdx, directIdx]
+    () => ({ isActive: urlActiveIdx === directIdx, selectTabInstant }),
+    [urlActiveIdx, directIdx, selectTabInstant]
   );
   const channelsPaneInfo = useMemo(
-    () => ({ isActive: urlActiveIdx === channelsIdx }),
-    [urlActiveIdx, channelsIdx]
+    () => ({ isActive: urlActiveIdx === channelsIdx, selectTabInstant }),
+    [urlActiveIdx, channelsIdx, selectTabInstant]
   );
   const botsPaneInfo = useMemo(
-    () => ({ isActive: urlActiveIdx === botsIdx }),
-    [urlActiveIdx, botsIdx]
+    () => ({ isActive: urlActiveIdx === botsIdx, selectTabInstant }),
+    [urlActiveIdx, botsIdx, selectTabInstant]
   );
 
   // The static header doesn't need useMatch of its own — `urlActiveIdx`

src/app/components/stream-header/StreamHeader.tsx

@@ -68,12 +68,34 @@ export function StreamHeader({ scrollRef, children, bottomPinned, pinKey }: Stre
   // MobileTabsPager, the shared static tabs row at the pager root
   // owns the visible segments + action icons; our local tabs row is
   // kept in DOM (preserving the curtain's TABS_ROW_PX-based snap
-  // geometry) but rendered with `visibility: hidden`. Only the
-  // currently active pane writes its curtain controls to
+  // geometry) but rendered with `opacity: 0` (still tap-able). Only
+  // the currently active pane writes its curtain controls to
   // `mobilePagerCurtainAtom` so the shared icons drive THIS curtain.
+  //
+  // `selectTabInstant` is the pager's tap-commit entrypoint: when our
+  // invisible per-pane Segments capture a tap (because the static
+  // header sits behind the strip in z-stack at rest), routing through
+  // this callback runs the same commit path as the static header's
+  // taps and suppresses the swipe-finish slide animation so tab
+  // switches feel snappy. Falls back to a plain `navigate(...)` on
+  // surfaces outside pager mode (desktop, non-listing routes).
   const pagerPane = useMobilePagerPane();
   const inPagerMode = pagerPane !== null;
   const isActivePagerPane = pagerPane?.isActive ?? false;
+  const selectTabInstant = pagerPane?.selectTabInstant ?? null;
+
+  const onSegmentDirect = useCallback(() => {
+    if (selectTabInstant) selectTabInstant('direct');
+    else navigate(DIRECT_PATH, navOpts);
+  }, [selectTabInstant, navigate, navOpts]);
+  const onSegmentChannels = useCallback(() => {
+    if (selectTabInstant) selectTabInstant('channels');
+    else navigate(CHANNELS_PATH, navOpts);
+  }, [selectTabInstant, navigate, navOpts]);
+  const onSegmentBots = useCallback(() => {
+    if (selectTabInstant) selectTabInstant('bots');
+    else navigate(BOTS_PATH, navOpts);
+  }, [selectTabInstant, navigate, navOpts]);
 
   const curtain = useCurtainState(pinKey);
 
@@ -216,40 +238,46 @@ export function StreamHeader({ scrollRef, children, bottomPinned, pinKey }: Stre
         {/* ── Tabs row + action icons (always visible) ───────────
             In pager mode the row stays mounted (curtain snap math
             depends on its TABS_ROW_PX height) but is painted invisible
-            because the shared static tabs row at the pager root owns
-            the visible chrome. Hit-testing the invisible row is fine —
-            the static header sits above it in z-stack and absorbs
-            taps; even if a tap leaked through, both rows trigger the
-            same navigate() so the user-visible result is identical.
+            via `opacity: 0` because the shared static tabs row at the
+            pager root owns the visible chrome. Critically opacity (not
+            `visibility: hidden`) keeps the row HIT-TESTABLE while
+            invisible — the strip's stacking context paints ON TOP of
+            the static pager header at rest (the curtain-rises-over-
+            header contract), so without per-pane taps the segments
+            would be unreachable. Both rows wire onClick to the same
+            navigate() destination, so whichever row captures the tap
+            the user-visible result is identical. The static header z-
+            elevates only while a horseshoe sheet is active and the
+            active pane isn't pinned — in that window the static header
+            sits above the strip and captures taps directly; the rest
+            of the time taps land on this opacity-0 row and resolve
+            through its own per-pane onClick handlers.
 
             `aria-hidden` removes the duplicate (per-pane) segments and
             icons from the accessibility tree so screen readers don't
             announce three sets of "Direct / Channels / Bots" plus the
-            single visible set from the shared static header. Chromium
-            already prunes `visibility: hidden` nodes from a11y, but
-            making the intent explicit guards against AT/browser
-            variations. */}
+            single visible set from the shared static header. */}
         <div
           className={css.tabsRow}
-          style={inPagerMode ? { visibility: 'hidden' } : undefined}
+          style={inPagerMode ? { opacity: 0 } : undefined}
           aria-hidden={inPagerMode || undefined}
         >
           <div className={css.tabsCluster}>
             <Segment
               active={!!directMatch}
               label={t('Direct.segment_dm')}
-              onClick={() => navigate(DIRECT_PATH, navOpts)}
+              onClick={onSegmentDirect}
             />
             <Segment
               active={!!channelsMatch}
               label={t('Direct.segment_channels')}
-              onClick={() => navigate(CHANNELS_PATH, navOpts)}
+              onClick={onSegmentChannels}
             />
             {showBotsSegment && (
               <Segment
                 active={!!botsMatch}
                 label={t('Direct.segment_bots')}
-                onClick={() => navigate(BOTS_PATH, navOpts)}
+                onClick={onSegmentBots}
               />
             )}
           </div>