diff --git a/frontend/package-lock.json b/frontend/package-lock.json
index dc2d63e2be89..2d1e17ac975a 100644
--- a/frontend/package-lock.json
+++ b/frontend/package-lock.json
@@ -163,7 +163,7 @@
         "@types/urijs": "^1.19.26",
         "@typescript-eslint/eslint-plugin": "8.69.0",
         "@typescript-eslint/parser": "8.69.0",
-        "@vitest/browser-playwright": "^4.1.10",
+        "@vitest/browser-playwright": "^4.1.11",
         "@vitest/coverage-v8": "^4.1.11",
         "@vitest/eslint-plugin": "^1.6.27",
         "angular-eslint": "^22.2.0",
diff --git a/frontend/package.json b/frontend/package.json
index 2fb9f22b1363..f31357f34d39 100644
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -33,7 +33,7 @@
     "@types/urijs": "^1.19.26",
     "@typescript-eslint/eslint-plugin": "8.69.0",
     "@typescript-eslint/parser": "8.69.0",
-    "@vitest/browser-playwright": "^4.1.10",
+    "@vitest/browser-playwright": "^4.1.11",
     "@vitest/coverage-v8": "^4.1.11",
     "@vitest/eslint-plugin": "^1.6.27",
     "angular-eslint": "^22.2.0",
diff --git a/frontend/src/app/shared/components/autocompleter/op-autocompleter/op-autocompleter.spec.ts b/frontend/src/app/shared/components/autocompleter/op-autocompleter/op-autocompleter.spec.ts
index 29f00c40d48e..11fba085b06c 100644
--- a/frontend/src/app/shared/components/autocompleter/op-autocompleter/op-autocompleter.spec.ts
+++ b/frontend/src/app/shared/components/autocompleter/op-autocompleter/op-autocompleter.spec.ts
@@ -251,11 +251,13 @@ describe('autocompleter', () => {
     });
 
     it('should recover and keep loading results after a lookup fails', () => {
+      const consoleError = vi.spyOn(console, 'error').mockImplementation(() => undefined);
+      const lookupError = new Error('backend rejected the query');
       vi.useFakeTimers();
       try {
         getOptionsFnSpy.mockImplementation((searchTerm:string) => {
           if (searchTerm === 'bad') {
-            return throwError(() => new Error('backend rejected the query'));
+            return throwError(() => lookupError);
           }
 
           return of(workPackagesStub).pipe(map((wps) => wps.filter((wp) => searchTerm !== '' && wp.subject.includes(searchTerm))));
@@ -279,6 +281,7 @@ describe('autocompleter', () => {
         fixture.detectChanges();
 
         expect(getOptionsFnSpy).toHaveBeenCalledWith('bad');
+        expect(consoleError).toHaveBeenCalledWith(lookupError);
         expect(select.itemsList.items.length).toEqual(0);
 
         inputElement.value = 'Wor';
@@ -438,6 +441,7 @@ describe('autocompleter', () => {
     });
 
     it('should load items with debounce', async () => {
+      silenceDestroyedOutputWarning();
       fixture.detectChanges();
 
       // Wait for ngAfterViewInit's internal setTimeout(25ms) and debounce to fire.
@@ -478,13 +482,12 @@ describe('autocompleter', () => {
   });
 });
 
-// NG0953 ("Unexpected emit for destroyed OutputRef") is emitted when ng-select
-// emits on an OutputRef during fixture teardown under fake timers. It is a real
-// lifecycle smell, not pure noise — silencing it here is a pragmatic stopgap so
-// these specs stay readable, not a fix. The proper fix is to stop the
-// emit-after-destroy in the component teardown path; until then this is
-// scoped to the two affected specs and passes every other warning through so it
-// does not hide unrelated regressions. Do not promote this to a global filter.
+// NG0953 ("Unexpected emit for destroyed OutputRef") comes from ng-select's
+// dropdown panel: `_measureDimensions` retries through a Promise and
+// requestAnimationFrame chain with no destroyed guard, so it emits after the
+// panel is torn down (https://github.com/ng-select/ng-select/issues/2869).
+// Silencing is a stopgap until ng-select guards that chain; it passes every
+// other warning through. Do not promote this to a global filter.
 function silenceDestroyedOutputWarning():void {
   const originalWarn = console.warn.bind(console);
 
diff --git a/frontend/src/app/shared/components/fields/edit/services/global-edit-form-changes-tracker/global-edit-form-changes-tracker.service.spec.ts b/frontend/src/app/shared/components/fields/edit/services/global-edit-form-changes-tracker/global-edit-form-changes-tracker.service.spec.ts
index 5e361d44607c..826e7f661944 100644
--- a/frontend/src/app/shared/components/fields/edit/services/global-edit-form-changes-tracker/global-edit-form-changes-tracker.service.spec.ts
+++ b/frontend/src/app/shared/components/fields/edit/services/global-edit-form-changes-tracker/global-edit-form-changes-tracker.service.spec.ts
@@ -53,6 +53,7 @@ describe('GlobalEditFormChangesTrackerService', () => {
   beforeEach(() => {
     originalOpenProject = window.OpenProject;
     window.OpenProject = new OpenProject();
+    vi.spyOn(window, 'confirm').mockReturnValue(false);
     TestBed.configureTestingModule({});
     service = TestBed.inject(GlobalEditFormChangesTrackerService);
   });
@@ -61,6 +62,7 @@ describe('GlobalEditFormChangesTrackerService', () => {
     // eslint-disable-next-line @typescript-eslint/dot-notation
     service['abortController'].abort();
     window.OpenProject = originalOpenProject;
+    vi.restoreAllMocks();
   });
 
   it('should be created', () => {
diff --git a/frontend/src/app/shared/directives/sortable-lists/sortable-lists.directive.behavior.spec.ts b/frontend/src/app/shared/directives/sortable-lists/sortable-lists.directive.behavior.spec.ts
index cd78031781fc..a409c05b678b 100644
--- a/frontend/src/app/shared/directives/sortable-lists/sortable-lists.directive.behavior.spec.ts
+++ b/frontend/src/app/shared/directives/sortable-lists/sortable-lists.directive.behavior.spec.ts
@@ -635,6 +635,7 @@ describe('sortable-lists directive group behavior', () => {
 
   describe('root teardown', () => {
     @Component({
+      selector: 'op-sortable-lists-teardown-host',
       imports: [OpSortableListsDirective, OpSortableListsListDirective, OpSortableListsItemDirective],
       template: `
         <div class="root" opSortableLists opSortableListsList>
diff --git a/frontend/src/stimulus/controllers/dynamic/work-packages/activities-tab/polling.controller.spec.ts b/frontend/src/stimulus/controllers/dynamic/work-packages/activities-tab/polling.controller.spec.ts
index 5fd953099765..2edfa830738f 100644
--- a/frontend/src/stimulus/controllers/dynamic/work-packages/activities-tab/polling.controller.spec.ts
+++ b/frontend/src/stimulus/controllers/dynamic/work-packages/activities-tab/polling.controller.spec.ts
@@ -164,13 +164,16 @@ describe('Activities tab polling controller', () => {
     });
 
     it('keeps polling after an error without an HTTP status', async () => {
+      const consoleError = vi.spyOn(console, 'error').mockImplementation(() => undefined);
+      const networkError = new Error('network hiccup');
       await renderPolling();
-      request.mockRejectedValue(new Error('network hiccup'));
+      request.mockRejectedValue(networkError);
 
       resolveContext(pluginContext());
       await vi.advanceTimersByTimeAsync(20000);
 
       expect(request).toHaveBeenCalledTimes(2);
+      expect(consoleError).toHaveBeenCalledWith('Error updating activities list:', networkError);
     });
   });
 });
diff --git a/frontend/src/test-browser-polyfills.ts b/frontend/src/test-browser-polyfills.ts
index e236a5d72211..366a4a6f146f 100644
--- a/frontend/src/test-browser-polyfills.ts
+++ b/frontend/src/test-browser-polyfills.ts
@@ -33,3 +33,12 @@ const globalWithProcess = globalThis as unknown as { process?:{ env:Record<strin
 if (typeof globalWithProcess.process === 'undefined') {
   globalWithProcess.process = { env: {} };
 }
+
+// Lit announces dev mode once per realm unless the warning is already recorded.
+// lit-html dedupes by code, @lit/reactive-element by the full message.
+const globalWithLitWarnings = globalThis as unknown as { litIssuedWarnings?:Set<string> };
+
+globalWithLitWarnings.litIssuedWarnings ??= new Set([
+  'dev-mode',
+  'Lit is in dev mode. Not recommended for production! See https://lit.dev/msg/dev-mode for more information.',
+]);