diff --git a/frontend/src/lib/shared/discussion/PersonMentionEditor.svelte.spec.ts b/frontend/src/lib/shared/discussion/PersonMentionEditor.svelte.spec.ts
index 0620ecfb..6d43d56b 100644
--- a/frontend/src/lib/shared/discussion/PersonMentionEditor.svelte.spec.ts
+++ b/frontend/src/lib/shared/discussion/PersonMentionEditor.svelte.spec.ts
@@ -219,30 +219,36 @@ describe('PersonMentionEditor — AC-2/3: search input drives fetch', () => {
 		expect(fetchesAfterSearch).toBe(1);
 	});
 
-	it('fires exactly one /api/persons fetch when the user searches for Walter (debounced)', async () => {
+	it('fires exactly one /api/persons fetch when the user searches for Walter (regression guard)', async () => {
+		// Regression guard: a previous version of PersonMentionEditor had a
+		// duplicated `items()` callback in the Tiptap suggestion config that
+		// fetched per-keystroke in addition to the debounced search-input fetch
+		// (Markus & Felix round-1). To catch that regression, we must NOT
+		// subtract any baseline — every fetch from render onwards counts.
+		// Sara on PR #629 round 3.
 		const fetchMock = vi
 			.fn()
 			.mockResolvedValue({ ok: true, json: vi.fn().mockResolvedValue([AUGUSTE]) });
 		vi.stubGlobal('fetch', fetchMock);
 		renderHost();
 
-		// Open the dropdown first so the search input is reachable. `fill` then
-		// drives the searchbox in one input event — sidesteps per-keystroke
-		// debounce timing on CI that Sara flagged on PR #629 round 2.
+		// Open the dropdown, then drive the search input via fill() — sidesteps
+		// per-keystroke timing of userEvent.type that Sara flagged round 2.
 		await userEvent.type(page.getByRole('textbox'), '@');
 		await vi.waitFor(async () => {
 			await expect.element(page.getByRole('searchbox')).toBeVisible();
 		});
-
-		const fetchesBeforeSearch = fetchMock.mock.calls.length;
-
 		await page.getByRole('searchbox').fill('Walter');
 
 		await new Promise((r) => setTimeout(r, SEARCH_DEBOUNCE_MS + POST_DEBOUNCE_SLACK_MS));
 
-		const personsFetches = fetchMock.mock.calls
-			.slice(fetchesBeforeSearch)
-			.filter(([url]) => typeof url === 'string' && url.startsWith('/api/persons'));
+		// No baseline subtraction — count ALL /api/persons fetches since render.
+		// If the legacy per-keystroke items() callback returns, typing `@` alone
+		// would already produce one fetch and `fill('Walter')` another, breaking
+		// this assertion.
+		const personsFetches = fetchMock.mock.calls.filter(
+			([url]) => typeof url === 'string' && url.startsWith('/api/persons')
+		);
 		expect(personsFetches.length).toBe(1);
 	});