diff --git a/src/view/PanelView.js b/src/view/PanelView.js
index 6918b61b0..0c6f8e0dd 100644
--- a/src/view/PanelView.js
+++ b/src/view/PanelView.js
@@ -365,13 +365,28 @@ define(function (require, exports, module) {
     /** @type {jQueryObject} Overflow dropdown button */
     let _$overflowBtn = null;
 
+    let _checkTabOverflowTimer = null;
+
     function _checkTabOverflow() {
+        // Coalesce multiple calls (e.g. rapid tab adds) and defer to the
+        // next frame so that measurements happen after layout settles.
+        if (_checkTabOverflowTimer) {
+            cancelAnimationFrame(_checkTabOverflowTimer);
+        }
+        _checkTabOverflowTimer = requestAnimationFrame(_doCheckTabOverflow);
+    }
+
+    function _doCheckTabOverflow() {
+        _checkTabOverflowTimer = null;
         if (!_$tabBar) {
             return;
         }
-        // Remove collapsed state first to measure true width
+
+        // Remove collapsed state first to measure true width.
+        // Use a 1px tolerance to avoid sub-pixel rounding flicker at
+        // boundary sizes (e.g. scrollWidth 678 vs clientWidth 677).
         _$tabBar.removeClass("bottom-panel-tabs-collapsed");
-        const isOverflowing = _$tabsOverflow[0].scrollWidth > _$tabsOverflow[0].clientWidth;
+        const isOverflowing = _$tabsOverflow[0].scrollWidth > _$tabsOverflow[0].clientWidth + 1;
         _$tabBar.toggleClass("bottom-panel-tabs-collapsed", isOverflowing);
 
         // Check if still overflowing after collapse
@@ -853,9 +868,11 @@ define(function (require, exports, module) {
             _toggleMaximize();
         });
 
-        // Re-check tab overflow when the tab bar resizes (e.g. window resize)
-        const tabBarResizeObserver = new ResizeObserver(_checkTabOverflow);
-        tabBarResizeObserver.observe(_$tabsOverflow[0]);
+        // Observe the outer tab bar container so that only external resizes
+        // (e.g. window resize, plugin panel open/close) trigger a re-check.
+        // Observing _$tabsOverflow would cause an infinite loop in WebKit
+        // because _checkTabOverflow toggles classes that change its size.
+        new ResizeObserver(_checkTabOverflow).observe(_$tabBar[0]);
 
         // Restore maximize state from preferences (survives reload).
         _isMaximized = PreferencesManager.getViewState(PREF_BOTTOM_PANEL_MAXIMIZED) === true;