diff --git a/static/boot.js b/static/boot.js
index 3ac19b5a..3bee6262 100644
--- a/static/boot.js
+++ b/static/boot.js
@@ -1918,27 +1918,25 @@ $('msg').addEventListener('input',()=>{
 });
 // #5514/#5515: re-pin the transcript on ANY composer height change, not only the
 // ones that route through the input->autoResize path. A multi-line paste
-// (WisprFlow), a draft restore, a programmatic value set, or a font/reflow can
-// all grow the composer and shrink the flex:1 transcript viewport, stranding a
-// pinned reader above the bottom (reads as a "random" upward jump — #5515). A
-// ResizeObserver on the textarea catches every case at one seam. The re-pin
-// itself is guarded (only fires when genuinely pinned), so this never fights a
-// reader who scrolled away. First callback fires on observe (initial size) — the
-// guard makes that a cheap no-op.
+// (WisprFlow), a draft restore, an attachment tray / selection-chip appearing, a
+// programmatic value set, or a font/reflow can all grow the composer and shrink
+// the flex:1 transcript viewport, stranding a pinned reader above the bottom
+// (reads as a "random" upward jump — #5515). Observe the whole #composerWrap
+// (not just #msg) so tray/chip growth is covered too, at one seam. The re-pin is
+// guarded (only fires when genuinely pinned), so it never fights a reader who
+// scrolled away. First callback fires on observe (initial size) — the guard
+// makes that a cheap no-op.
 (()=>{
-  const _c=$('msg');
-  if(!_c || typeof ResizeObserver!=='function' || typeof _repinMessagesAfterComposerResize!=='function') return;
-  let _lastComposerH=_c.offsetHeight;
+  const _cw=$('composerWrap')||$('msg');
+  if(!_cw || typeof ResizeObserver!=='function' || typeof _repinMessagesAfterComposerResize!=='function') return;
+  let _lastComposerH=_cw.offsetHeight;
   const _ro=new ResizeObserver(()=>{
-    const h=_c.offsetHeight;
-    if(h===_lastComposerH) return;   // width-only / no-op resize: ignore
-    const grew=h>_lastComposerH;
+    const h=_cw.offsetHeight;
+    if(h<=_lastComposerH){_lastComposerH=h;return;}   // shrink/no-op: enlarges the viewport, can't strand
     _lastComposerH=h;
-    // Only a GROW shrinks the transcript viewport; a shrink enlarges it and can't
-    // strand a pinned reader. Re-pin on grow.
-    if(grew) _repinMessagesAfterComposerResize();
+    _repinMessagesAfterComposerResize();               // grow: re-pin the pinned reader
   });
-  try{ _ro.observe(_c); }catch(_){ }
+  try{ _ro.observe(_cw); }catch(_){ }
 })();
 // Track IME composition for East Asian input. Safari fires the committing
 // keydown AFTER compositionend with isComposing=false, so we also keep a
diff --git a/static/ui.js b/static/ui.js
index 5f3ba8dd..0719a52b 100644
--- a/static/ui.js
+++ b/static/ui.js
@@ -5395,7 +5395,7 @@ function _repinMessagesAfterComposerResize(){
   if(!el) return;
   // Already at/very near the bottom? nothing to do (avoids needless writes while
   // idle-reading a short conversation that isn't scrollable).
-  if(el.scrollHeight-el.scrollTop-el.clientHeight<=1) return;
+  if(_messageBottomDistance()<=1) return;
   if(typeof _setMessageScrollToBottom==='function') _setMessageScrollToBottom();
   else { el.scrollTop=el.scrollHeight; }
 }
diff --git a/tests/test_issue5514_composer_grow_scroll_pin.py b/tests/test_issue5514_composer_grow_scroll_pin.py
index affbbf54..1ac95bb5 100644
--- a/tests/test_issue5514_composer_grow_scroll_pin.py
+++ b/tests/test_issue5514_composer_grow_scroll_pin.py
@@ -70,11 +70,14 @@ def test_autoresize_calls_the_repin():
 
 
 def test_resize_observer_installed_on_composer():
-    # A ResizeObserver on #msg re-pins on grow (catches non-autoResize paths).
+    # A ResizeObserver on the composer wrapper re-pins on grow (catches
+    # tray/chip/paste height changes, not just the typed-input seam).
     assert "new ResizeObserver(" in BOOT_JS
     assert "_repinMessagesAfterComposerResize" in BOOT_JS
+    # Observes the whole wrapper so attach-tray / selection-chip growth is covered.
+    assert "$('composerWrap')" in BOOT_JS
     # Only re-pin on GROW (a shrink enlarges the viewport, can't strand a reader).
-    assert "if(grew) _repinMessagesAfterComposerResize();" in BOOT_JS
+    assert "can't strand" in BOOT_JS
 
 
 # ---------------------------------------------------------------------------
@@ -94,6 +97,7 @@ def _run(scenario):
         // messages pane: scrollHeight fixed; clientHeight shrinks when composer grows.
         const el = { scrollHeight: 8768, clientHeight: 745, scrollTop: %(scrolltop)s };
         const $ = (id) => (id === 'messages' ? el : null);
+        function _messageBottomDistance(){ return el.scrollHeight - el.scrollTop - el.clientHeight; }
         function _setMessageScrollToBottom(){ el.scrollTop = el.scrollHeight - el.clientHeight; el._pinnedCalled = true; }
 
         %(helper)s