lib/theme/design_tokens.dart

@@ -133,7 +133,12 @@ class NooColors extends ThemeExtension<NooColors> {
   /// palettes. `success`/`successSoft`/`warning`/`warningSoft`/`info`/
   /// `infoSoft` have no Material dynamic equivalent and are content-identity
   /// colors regardless (file-type tiles) rather than brand colors, so they
-  /// always come from the fixed palette matching [cs]'s brightness.
+  /// always come from the fixed palette matching [cs]'s brightness. Same
+  /// for `scrim`: Material 3's `ColorScheme.scrim` role is fully *opaque*
+  /// black (`0xFF000000`), meant to be used at reduced opacity by whoever
+  /// paints it, not painted directly - using it as-is for a sheet/dialog's
+  /// `barrierColor` hid the screen behind completely instead of dimming it,
+  /// so this uses the fixed palette's already-translucent scrim instead.
   factory NooColors.fromDynamicScheme(ColorScheme cs) {
     final fixed = cs.brightness == Brightness.dark ? dark : light;
     return NooColors(
@@ -157,7 +162,7 @@ class NooColors extends ThemeExtension<NooColors> {
       warningSoft: fixed.warningSoft,
       info: fixed.info,
       infoSoft: fixed.infoSoft,
-      scrim: cs.scrim,
+      scrim: fixed.scrim,
     );
   }
 

lib/widgets/details/details_sheet.dart

@@ -96,7 +96,12 @@ class DetailsSheet extends StatelessWidget {
 /// [StatefulWidget] rather than three fields on [DetailsSheet] so the
 /// selection survives independently of how the header/container around it
 /// is built (mobile embeds this once, desktop hands it to [showNooDialog]
-/// directly).
+/// directly). All three tabs are built once and kept mounted in an
+/// [IndexedStack] rather than swapped in/out of the tree - Versions and
+/// Activity each fetch on their own first build (see their `_requested`
+/// guard), so switching tabs via a bare `switch` on the selected type would
+/// tear down and rebuild whichever tab isn't showing, discarding its
+/// fetched data and re-requesting it every time the user switched back.
 class _DetailsBody extends StatefulWidget {
   final NextcloudItem item;
 
@@ -138,11 +143,14 @@ class _DetailsBodyState extends State<_DetailsBody> {
           ],
         ),
         const SizedBox(height: NooSpace.lg),
-        switch (_tab) {
-          _DetailsTab.info => DetailsInfoTab(item: widget.item),
-          _DetailsTab.versions => DetailsVersionsTab(item: widget.item),
-          _DetailsTab.activity => DetailsActivityTab(item: widget.item),
-        },
+        IndexedStack(
+          index: _tab.index,
+          children: [
+            DetailsInfoTab(item: widget.item),
+            DetailsVersionsTab(item: widget.item),
+            DetailsActivityTab(item: widget.item),
+          ],
+        ),
       ],
     );
   }

test/widgets/noo/core_test.dart

@@ -57,6 +57,22 @@ void main() {
     });
   });
 
+  group('NooColors.fromDynamicScheme', () {
+    test('scrim comes from the fixed palette, not the opaque dynamic role', () {
+      // Material 3's ColorScheme.scrim is fully opaque black - using it
+      // directly as a sheet/dialog barrierColor hid the screen behind
+      // completely instead of dimming it.
+      final dynamicScheme = ColorScheme.fromSeed(
+        seedColor: const Color(0xFF009688),
+        brightness: Brightness.light,
+      );
+      expect(dynamicScheme.scrim.a, 1.0);
+      final nooColors = NooColors.fromDynamicScheme(dynamicScheme);
+      expect(nooColors.scrim, NooColors.light.scrim);
+      expect(nooColors.scrim.a, lessThan(1.0));
+    });
+  });
+
   group('NooAvatar', () {
     testNooWidgets('current user uses accent-soft/accent-text', (
       tester,