diff --git a/changelog.md b/changelog.md
index 36afd46..b4ec99a 100644
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,13 @@
 # Changelog
 
+## 2025-12-29 - 3.7.1 - fix(dees-appui-maincontent)
+migrate main content layout to CSS Grid and enable topbar collapse transitions
+
+- Replace absolute positioning with CSS Grid on :host and .maincontainer to enable natural document flow
+- Make .topbar a grid and animate collapse via grid-template-rows; switch :host([notabs]) to grid-template-rows: 0fr instead of display:none to allow transitions
+- Set .maincontainer to display:contents and add min-height:0 on content areas and topbar children to fix overflow/scrolling and flex/grid height issues
+- Remove positional styles (position:absolute/top/left/right/bottom) so content scrolls correctly and layout is more robust
+
 ## 2025-12-29 - 3.7.0 - feat(dees-contextmenu,dees-appui-tabs,test)
 Prevent double-destruction of context menus, await window layer teardown, update destroyAll behavior, remove tabs content slot, and adjust tests
 
diff --git a/ts_web/00_commitinfo_data.ts b/ts_web/00_commitinfo_data.ts
index 9c90516..b3deea1 100644
--- a/ts_web/00_commitinfo_data.ts
+++ b/ts_web/00_commitinfo_data.ts
@@ -3,6 +3,6 @@
  */
 export const commitinfo = {
   name: '@design.estate/dees-catalog',
-  version: '3.7.0',
+  version: '3.7.1',
   description: 'A comprehensive library that provides dynamic web components for building sophisticated and modern web applications using JavaScript and TypeScript.'
 }
diff --git a/ts_web/elements/00group-appui/dees-appui-maincontent/dees-appui-maincontent.ts b/ts_web/elements/00group-appui/dees-appui-maincontent/dees-appui-maincontent.ts
index 77a653a..629d19d 100644
--- a/ts_web/elements/00group-appui/dees-appui-maincontent/dees-appui-maincontent.ts
+++ b/ts_web/elements/00group-appui/dees-appui-maincontent/dees-appui-maincontent.ts
@@ -53,41 +53,36 @@ export class DeesAppuiMaincontent extends DeesElement {
       /* TODO: Migrate hardcoded values to --dees-* CSS variables */
       :host {
         color: ${cssManager.bdTheme('#333', '#fff')};
-        display: block;
+        display: grid;
+        grid-template-rows: auto 1fr;
         width: 100%;
         height: 100%;
-        position: relative;
         background: ${cssManager.bdTheme('#ffffff', '#161616')};
       }
+
       .maincontainer {
-        position: absolute;
-        height: 100%;
-        right: 0px;
-        top: 0px;
-        width: 100%;
+        display: contents;
       }
 
       .topbar {
-        position: absolute;
-        width: 100%;
+        display: grid;
+        grid-template-rows: 1fr;
+        overflow: hidden;
         user-select: none;
+        transition: grid-template-rows 0.3s ease;
+      }
+
+      .topbar > * {
+        min-height: 0;
       }
 
       .content-area {
-        position: absolute;
-        top: 60px;
-        left: 0;
-        right: 0;
-        bottom: 0;
         overflow: auto;
+        min-height: 0;
       }
 
       :host([notabs]) .topbar {
-        display: none;
-      }
-
-      :host([notabs]) .content-area {
-        top: 0;
+        grid-template-rows: 0fr;
       }
     `,
   ];