diff --git a/frontend/src/lib/shared/discussion/mention.spec.ts b/frontend/src/lib/shared/discussion/mention.spec.ts
index f063ab3b..a049d669 100644
--- a/frontend/src/lib/shared/discussion/mention.spec.ts
+++ b/frontend/src/lib/shared/discussion/mention.spec.ts
@@ -307,9 +307,21 @@ describe('renderTranscriptionBody', () => {
 		expect(result).not.toMatch(/>O"Brien<\/a>/);
 	});
 
-	it('renders nothing when mentionedPersons is undefined-empty and no @ triggers', () => {
-		const result = renderTranscriptionBody('Plain old transcription text.', []);
-		expect(result).toBe('Plain old transcription text.');
+	it('renders a deleted-person @mention as plain text with no dead link (graceful degradation)', () => {
+		// AC-6 (#684): when a mentioned person is deleted, V71's ON DELETE CASCADE removes the
+		// sidecar row, so the displayName reaches the renderer with an empty mentionedPersons
+		// array. The reader must still see the name as plain text — never a dead <a>, a
+		// person-mention class, a data-person-id, or an href. This locks the degradation
+		// contract so a future renderer refactor cannot silently reintroduce a dead link.
+		const result = renderTranscriptionBody('Brief an @Auguste Raddatz vom Mai', []);
+		// (a) the reader still sees the readable name and the surrounding sentence verbatim
+		expect(result).toContain('Auguste Raddatz');
+		expect(result).toBe('Brief an @Auguste Raddatz vom Mai');
+		// (b) none of the anchor artifacts leak through
+		expect(result).not.toContain('<a');
+		expect(result).not.toContain('person-mention');
+		expect(result).not.toContain('data-person-id');
+		expect(result).not.toContain('href');
 	});
 
 	it('skips substitution when personId is not a UUID (defense in depth)', () => {