diff --git a/packages/base-styles/CHANGELOG.md b/packages/base-styles/CHANGELOG.md
index 39f957feddf0a4..ea8fd6930841b2 100644
--- a/packages/base-styles/CHANGELOG.md
+++ b/packages/base-styles/CHANGELOG.md
@@ -6,6 +6,7 @@
 
 -   Remove `.components-resizable-box__handle`, `.components-resizable-box__side-handle`, and `.components-resizable-box__corner-handle` from the `z-index()` helper ([#77620](https://github.com/WordPress/gutenberg/pull/77620)).
 -   Remove `.components-form-toggle__input` from the `z-index()` helper ([#77619](https://github.com/WordPress/gutenberg/pull/77619)).
+-   Remove `.interface-complementary-area .components-panel` and `.interface-complementary-area .components-panel__header` from the `z-index()` helper ([#77717](https://github.com/WordPress/gutenberg/pull/77717)).
 -   Remove `.components-button {:focus or .is-primary}` from the `z-index()` helper ([#77621](https://github.com/WordPress/gutenberg/pull/77621)).
 
 ## 6.20.0 (2026-04-15)
diff --git a/packages/base-styles/_z-index.scss b/packages/base-styles/_z-index.scss
index 1fdd582f4f9a10..b2a715487a9fba 100644
--- a/packages/base-styles/_z-index.scss
+++ b/packages/base-styles/_z-index.scss
@@ -17,10 +17,6 @@ $z-layers: (
 	".block-library-query-pattern__selection-search": 2, // higher sticky element
 	".editor-post-template__swap-template-search": 2, // higher sticky element
 
-	// These next two share a stacking context
-	".interface-complementary-area .components-panel" : 0, // lower scrolling content
-	".interface-complementary-area .components-panel__header": 1, // higher sticky element
-
 	".components-modal__header": 10,
 	".edit-post-meta-boxes-area.is-loading::before": 1,
 	".edit-post-meta-boxes-area .spinner": 5,
diff --git a/packages/interface/src/components/complementary-area/style.scss b/packages/interface/src/components/complementary-area/style.scss
index 10e8fde9769241..48770165594b1a 100644
--- a/packages/interface/src/components/complementary-area/style.scss
+++ b/packages/interface/src/components/complementary-area/style.scss
@@ -1,7 +1,6 @@
 @use "@wordpress/base-styles/colors" as *;
 @use "@wordpress/base-styles/mixins" as *;
 @use "@wordpress/base-styles/variables" as *;
-@use "@wordpress/base-styles/z-index" as *;
 
 .interface-complementary-area {
 	background: $white;
@@ -17,13 +16,14 @@
 		border: none;
 		// Make a stacking context that keeps all descendents behind the sticky header
 		position: relative;
-		z-index: z-index(".interface-complementary-area .components-panel");
+		z-index: 0;
 	}
 
 	.components-panel__header {
 		position: sticky;
 		top: 0;
-		z-index: z-index(".interface-complementary-area .components-panel__header");
+		// Sit above the panel's scrolling content within the stacking context above.
+		z-index: 1;
 
 		&.editor-sidebar__panel-tabs {
 			top: 0;