diff --git a/static/ui.js b/static/ui.js
index eada54bb..63535edc 100644
--- a/static/ui.js
+++ b/static/ui.js
@@ -15245,6 +15245,10 @@ function _restoreMessageScrollSnapshotSameFrame(snapshot){
   if(!restoredViaAnchor){
     const maxTop=Math.max(0,el.scrollHeight-el.clientHeight);
     const bottom=Number(snapshot.bottom);
+    // Mobile/touch viewports have native overflow anchoring to hold an
+    // unpinned reader across a rebuild. Desktop deliberately disables that
+    // browser behavior, so it must continue into the explicit fallback below.
+    const _fbTouchHold=(typeof _isTouchLikeMessageViewport==='function' && _isTouchLikeMessageViewport(el));
     // #5637: when the reader has scrolled UP into history (userUnpinned) and the
     // semantic anchor restore failed, do NOT snap scrollTop to the captured
     // ABSOLUTE snapshot.top. During streaming, the live activity-scene refresh
@@ -15254,7 +15258,7 @@ function _restoreMessageScrollSnapshotSameFrame(snapshot){
     // untouched lets the browser's own scroll anchoring hold the reader's
     // position. Pinned / near-bottom readers still get the tail-relative restore
     // below (that path is correct and must run).
-    if(snapshot.userUnpinned===true&&snapshot.pinned!==true){
+    if(snapshot.userUnpinned===true&&snapshot.pinned!==true&&_fbTouchHold){
       _lastScrollTop=el.scrollTop;_lastMessageClientHeight=el.clientHeight;
       _messageUserUnpinned=true;
       _scrollPinned=false;
@@ -15285,7 +15289,6 @@ function _restoreMessageScrollSnapshotSameFrame(snapshot){
     const _grewSinceSnap=Number.isFinite(_snapSH)&&_snapSH>0&&(el.scrollHeight-_snapSH)>4;
     const _fbActiveIntent=(typeof _recentMessageScrollIntent==='function' && _recentMessageScrollIntent())
       || (typeof _recentMessageTouchScrollIntent==='function' && _recentMessageTouchScrollIntent());
-    const _fbTouchHold=(typeof _isTouchLikeMessageViewport==='function' && _isTouchLikeMessageViewport(el));
     if(_fbTouchHold && snapshot.pinned!==true && _grewSinceSnap && !_fbActiveIntent
        && Math.abs((Math.max(0,Math.min(target,maxTop)))-el.scrollTop)>8){
       _lastScrollTop=el.scrollTop;_lastMessageClientHeight=el.clientHeight;
diff --git a/tests/test_issue5637_mobile_scroll_clamp_jumpback.py b/tests/test_issue5637_mobile_scroll_clamp_jumpback.py
index d69c63f9..c999d597 100644
--- a/tests/test_issue5637_mobile_scroll_clamp_jumpback.py
+++ b/tests/test_issue5637_mobile_scroll_clamp_jumpback.py
@@ -94,17 +94,19 @@ def test_content_visibility_scoped_to_user_rows():
     )
 
 
-def test_restore_same_frame_holds_position_for_unpinned_reader():
-    """The absolute-top fallback must be skipped for an unpinned reader.
+def test_restore_same_frame_holds_position_for_unpinned_touch_reader():
+    """The absolute-top fallback must be skipped when native anchoring can hold.
 
     When the reader is scrolled up (userUnpinned) and the anchor restore failed,
     _restoreMessageScrollSnapshotSameFrame must NOT write an absolute snapshot.top
     (it goes stale and nudges the viewport backward as scrollHeight grows, #5637).
-    It should hold position and return before the el.scrollTop write.
+    It should hold position and return before the el.scrollTop write. Desktop
+    intentionally falls through to the explicit fallback because it has no
+    native overflow-anchor layer.
     """
     fn = _restore_same_frame_fn()
-    assert "snapshot.userUnpinned===true&&snapshot.pinned!==true" in fn, (
-        "The fallback must guard the unpinned/anchor-failed case (#5637)."
+    assert "snapshot.userUnpinned===true&&snapshot.pinned!==true&&_fbTouchHold" in fn, (
+        "The fallback must guard the unpinned/anchor-failed touch case (#5637)."
     )
     # The guard must sit BEFORE the absolute-top scrollTop write and short-circuit it.
     guard_idx = fn.index("snapshot.userUnpinned===true&&snapshot.pinned!==true")
diff --git a/tests/test_issue5637_stale_anchor_guard.py b/tests/test_issue5637_stale_anchor_guard.py
index 3b83c094..e06e6c28 100644
--- a/tests/test_issue5637_stale_anchor_guard.py
+++ b/tests/test_issue5637_stale_anchor_guard.py
@@ -175,6 +175,7 @@ def test_realign_allows_on_desktop_no_native_anchor():
 def _fallback_harness(*, snapshot_scroll_height, cur_scroll_height, snapshot_top,
                       active_intent: bool = False, touch_like: bool = True,
                       init_scroll_top: int = 90030,
+                      snapshot_user_unpinned: bool = False,
                       anchor=None, anchor_row_content_pos=None, container_top: int = 0,
                       top_pad_now=None) -> str:
     """Node harness for the absolute-fallback path of _restoreMessageScrollSnapshotSameFrame.
@@ -241,7 +242,7 @@ function _deferClearProgrammaticScroll(){{}}
 function requestAnimationFrame(cb){{ cb(); }}
 function setTimeout(cb){{ cb(); return 1; }}
 const snapshot = {{ anchor: {anchor_js}, top: {snapshot_top}, bottom: 40,
-  scrollHeight: {sh}, pinned: false, userUnpinned: false }};
+  scrollHeight: {sh}, pinned: false, userUnpinned: {str(snapshot_user_unpinned).lower()} }};
 eval(extractFunc('_desktopAnchorRealignDelta'));
 eval(extractFunc('_restoreMessageScrollSnapshotSameFrame'));
 _restoreMessageScrollSnapshotSameFrame(snapshot);
@@ -312,6 +313,21 @@ def test_fallback_allows_snapshot_top_on_desktop_no_native_anchor():
     assert m["messageUserUnpinned"] is False and m["scrollPinned"] is True
 
 
+def test_unpinned_anchor_miss_restores_on_desktop_without_native_anchor():
+    """A desktop reader who deliberately scrolled up cannot be left to native
+    anchoring: desktop disables it. If the semantic row is temporarily absent,
+    the rebuild may clamp scrollTop toward zero before this function runs, so the
+    fallback must restore the snapshot rather than taking the mobile no-write exit.
+    """
+    m = json.loads(_run_node(_fallback_harness(
+        snapshot_scroll_height=90000, cur_scroll_height=90453, snapshot_top=89577,
+        active_intent=False, touch_like=False, snapshot_user_unpinned=True,
+        init_scroll_top=0,
+    )))
+    assert m["writes"] == [89577]
+    assert m["messageUserUnpinned"] is True and m["scrollPinned"] is False
+
+
 # ---- round-3 desktop anchor-realign (PR #5742): app's own scrollTop += delta idiom -----
 # These use SCROLL-DEPENDENT rect mocks (rect.top = rowContentPos - scrollTop), so the
 # certified hold numbers are physically realizable in a real browser — the round-2
@@ -479,6 +495,7 @@ def test_predicate_stays_true_on_touch_when_inline_anchor_clobbered_to_none():
     assert m["touchLike"] is True
 
 
+
 def test_predicate_false_on_desktop_fine_pointer():
     """Desktop (fine pointer): matchMedia('(pointer:coarse)') is false and the resting
     computed overflow-anchor is 'none' -> predicate reports NOT touch, so the guards do
@@ -546,4 +563,3 @@ def test_predicate_true_on_android_not_ios():
         platform="Linux armv8l", max_touch_points=5,
     )))
     assert m["touchLike"] is True
-