diff --git a/frontend/src/routes/DropZone.svelte.test.ts b/frontend/src/routes/DropZone.svelte.test.ts
index c4399c85..2499b3dd 100644
--- a/frontend/src/routes/DropZone.svelte.test.ts
+++ b/frontend/src/routes/DropZone.svelte.test.ts
@@ -47,16 +47,17 @@ describe('DropZone', () => {
 		await expect.element(page.getByText(/Dateiformat nicht unterstützt/i)).toBeVisible();
 	});
 
-	it('accepts a PDF file as a valid type', async () => {
+	it('accepts a PDF file as a valid type and renders no "invalid type" message', async () => {
 		const onUploadComplete = vi.fn();
 		render(DropZone, { props: { onUploadComplete } });
 
 		const input = document.querySelector('input[type="file"]') as HTMLInputElement;
 		const pdfFile = new File(['%PDF'], 'brief.pdf', { type: 'application/pdf' });
 		Object.defineProperty(input, 'files', { value: [pdfFile], writable: false });
+		input.dispatchEvent(new Event('change', { bubbles: true }));
 
-		// Just verify the change event triggers without throwing
-		expect(() => input.dispatchEvent(new Event('change', { bubbles: true }))).not.toThrow();
+		// The validation guard never raises an invalid-type error for application/pdf.
+		expect(document.body.textContent).not.toMatch(/Dateiformat nicht unterstützt/i);
 	});
 
 	it('returns early when no files are selected', async () => {
@@ -66,7 +67,6 @@ describe('DropZone', () => {
 		Object.defineProperty(input, 'files', { value: [], writable: false });
 		input.dispatchEvent(new Event('change', { bubbles: true }));
 
-		// No error message rendered
 		const errors = document.querySelectorAll('.text-red-600');
 		expect(errors.length).toBe(0);
 	});
@@ -105,9 +105,10 @@ describe('DropZone', () => {
 		const dropZone = document.querySelector('div[role="button"]') as HTMLElement;
 		dropZone.dispatchEvent(new DragEvent('dragover', { bubbles: true }));
 
-		// The dragging class is applied via reactive isDragging
-		await new Promise((r) => setTimeout(r, 30));
-		expect(dropZone.className).toMatch(/border-primary|bg-accent-bg/);
+		// isDragging=true switches the class to border-primary bg-accent-bg — wait for the next paint.
+		await vi.waitFor(() => {
+			expect(dropZone.className).toMatch(/bg-accent-bg/);
+		});
 	});
 
 	it('drops dragging style on dragleave', async () => {
@@ -115,22 +116,27 @@ describe('DropZone', () => {
 
 		const dropZone = document.querySelector('div[role="button"]') as HTMLElement;
 		dropZone.dispatchEvent(new DragEvent('dragover', { bubbles: true }));
-		await new Promise((r) => setTimeout(r, 10));
+		await vi.waitFor(() => {
+			expect(dropZone.className).toMatch(/bg-accent-bg/);
+		});
 		dropZone.dispatchEvent(new DragEvent('dragleave', { bubbles: true }));
-		await new Promise((r) => setTimeout(r, 30));
-		expect(dropZone.className).not.toMatch(/^border-primary bg-accent-bg/);
+		await vi.waitFor(() => {
+			expect(dropZone.className).not.toMatch(/bg-accent-bg/);
+		});
 	});
 
-	it('handles drop event without files (no-op)', async () => {
+	it('drop event with no files is a no-op (no error message)', async () => {
 		render(DropZone, { props: {} });
 
 		const dropZone = document.querySelector('div[role="button"]') as HTMLElement;
 		const dropEvent = new DragEvent('drop', { bubbles: true });
 		Object.defineProperty(dropEvent, 'dataTransfer', { value: { files: [] }, writable: false });
-		expect(() => dropZone.dispatchEvent(dropEvent)).not.toThrow();
+		dropZone.dispatchEvent(dropEvent);
+
+		expect(document.querySelectorAll('.text-red-600')).toHaveLength(0);
 	});
 
-	it('rejects multiple invalid files and lists them all', async () => {
+	it('rejects multiple invalid files and lists one error message per file', async () => {
 		render(DropZone, { props: {} });
 
 		const input = document.querySelector('input[type="file"]') as HTMLInputElement;
@@ -139,19 +145,21 @@ describe('DropZone', () => {
 		Object.defineProperty(input, 'files', { value: [f1, f2], writable: false });
 		input.dispatchEvent(new Event('change', { bubbles: true }));
 
-		await new Promise((r) => setTimeout(r, 30));
-		const errors = document.querySelectorAll('.text-red-600');
-		expect(errors.length).toBe(2);
+		await vi.waitFor(() => {
+			expect(document.querySelectorAll('.text-red-600')).toHaveLength(2);
+		});
 	});
 
-	it('mixes valid and invalid files without throwing during upload', async () => {
+	it('mixed valid+invalid files raises an error only for the invalid one', async () => {
 		render(DropZone, { props: {} });
 
 		const input = document.querySelector('input[type="file"]') as HTMLInputElement;
 		const f1 = new File(['x'], 'a.docx', { type: 'application/x-bad' });
 		const f2 = new File(['%PDF'], 'b.pdf', { type: 'application/pdf' });
 		Object.defineProperty(input, 'files', { value: [f1, f2], writable: false });
-		expect(() => input.dispatchEvent(new Event('change', { bubbles: true }))).not.toThrow();
+		input.dispatchEvent(new Event('change', { bubbles: true }));
+
+		await expect.element(page.getByText(/Dateiformat nicht unterstützt/i)).toBeVisible();
 	});
 
 	it('Enter handler ignores other keys', async () => {
@@ -167,26 +175,35 @@ describe('DropZone', () => {
 	it('responds to window-level dragenter only when dataTransfer.types includes "Files"', async () => {
 		render(DropZone, { props: {} });
 
-		// Non-files dragenter should not trigger windowDragging
+		const dropZone = document.querySelector('div[role="button"]') as HTMLElement;
+
+		// Non-files dragenter should not trigger the windowDragging style.
 		const evt1 = new DragEvent('dragenter', { bubbles: true });
 		Object.defineProperty(evt1, 'dataTransfer', { value: { types: ['text/html'] } });
 		window.dispatchEvent(evt1);
-		await new Promise((r) => setTimeout(r, 10));
+		expect(dropZone.className).not.toMatch(/bg-accent-bg/);
 
-		// Files dragenter should — we just confirm no error
+		// Files dragenter flips windowDragging=true → drop-zone gains the border-primary style.
 		const evt2 = new DragEvent('dragenter', { bubbles: true });
 		Object.defineProperty(evt2, 'dataTransfer', { value: { types: ['Files'] } });
-		expect(() => window.dispatchEvent(evt2)).not.toThrow();
+		window.dispatchEvent(evt2);
+		await vi.waitFor(() => {
+			expect(dropZone.className).toMatch(/bg-accent-bg/);
+		});
 
-		// Trailing window drop to clean up
+		// Trailing window drop to clean up.
 		window.dispatchEvent(new DragEvent('drop', { bubbles: true }));
 	});
 
-	it('window-level dragleave decrements counter without going negative', async () => {
+	it('window-level dragleave without prior dragenter is safe (counter does not go negative)', async () => {
 		render(DropZone, { props: {} });
 
-		// Multiple dragleaves without dragenters should not throw
-		expect(() => window.dispatchEvent(new DragEvent('dragleave', { bubbles: true }))).not.toThrow();
-		expect(() => window.dispatchEvent(new DragEvent('dragleave', { bubbles: true }))).not.toThrow();
+		const dropZone = document.querySelector('div[role="button"]') as HTMLElement;
+
+		// Two consecutive dragleaves on the window without dragenters should leave the drop-zone
+		// in its idle (non-highlighted) state.
+		window.dispatchEvent(new DragEvent('dragleave', { bubbles: true }));
+		window.dispatchEvent(new DragEvent('dragleave', { bubbles: true }));
+		expect(dropZone.className).not.toMatch(/bg-accent-bg/);
 	});
 });