diff --git a/packages/vscode-ide-companion/src/webview/components/SessionHistoryDropdown.test.tsx b/packages/vscode-ide-companion/src/webview/components/SessionHistoryDropdown.test.tsx
index 27180638b70..8e0dc8ee307 100644
--- a/packages/vscode-ide-companion/src/webview/components/SessionHistoryDropdown.test.tsx
+++ b/packages/vscode-ide-companion/src/webview/components/SessionHistoryDropdown.test.tsx
@@ -176,3 +176,89 @@ describe('SessionHistoryDropdown pagination', () => {
     expect(onLoadMore).toHaveBeenCalledTimes(1);
   });
 });
+
+describe('SessionHistoryDropdown calendar-week grouping', () => {
+  afterEach(() => {
+    vi.useRealTimers();
+  });
+
+  function sessionAt(sessionId: string, updatedAt: Date): DaemonSessionSummary {
+    const stamp = updatedAt.toISOString();
+    return {
+      sessionId,
+      workspaceCwd: '/workspace',
+      displayName: sessionId,
+      createdAt: stamp,
+      updatedAt: stamp,
+    };
+  }
+
+  async function renderWithSessions(sessions: DaemonSessionSummary[]) {
+    const container = document.createElement('div');
+    document.body.appendChild(container);
+    const root = createRoot(container);
+    await act(async () => {
+      root.render(
+        <SessionHistoryDropdown
+          t={t}
+          sessions={sessions}
+          searchQuery=""
+          loading={false}
+          hasMore={false}
+          onSearchChange={() => {}}
+          onSelect={() => {}}
+          onRename={async () => {}}
+          onDelete={async () => {}}
+          onLoadMore={() => {}}
+          onClose={() => {}}
+        />,
+      );
+      await Promise.resolve();
+    });
+    mounted.push({ container, root });
+    return container;
+  }
+
+  function groupLabels(container: HTMLElement): string[] {
+    return Array.from(container.querySelectorAll('[role="group"]')).map(
+      (group) => group.getAttribute('aria-label') ?? '',
+    );
+  }
+
+  it('buckets a Saturday session as older on the following Monday', async () => {
+    // Monday 2026-11-02: a rolling 168h window would still call last Saturday
+    // "this week", but the calendar week started today.
+    vi.useFakeTimers({ toFake: ['Date'] });
+    vi.setSystemTime(new Date(2026, 10, 2, 12));
+
+    const container = await renderWithSessions([
+      sessionAt('last-saturday', new Date(2026, 9, 31, 12)),
+    ]);
+
+    const labels = groupLabels(container);
+    expect(labels).not.toContain(t('group.thisWeek'));
+    expect(labels).toContain(t('group.older'));
+    const row = container.querySelector('[data-session-id="last-saturday"]');
+    expect(row?.closest('[role="group"]')?.getAttribute('aria-label')).toBe(
+      t('group.older'),
+    );
+  });
+
+  it('keeps a Wednesday session in this week on the following Friday', async () => {
+    // Positive control: the This Week bucket still exists mid-week, so the
+    // Monday assertion above cannot pass merely because the group never shows.
+    vi.useFakeTimers({ toFake: ['Date'] });
+    vi.setSystemTime(new Date(2026, 10, 6, 12));
+
+    const container = await renderWithSessions([
+      sessionAt('wednesday', new Date(2026, 10, 4, 12)),
+    ]);
+
+    const labels = groupLabels(container);
+    expect(labels).toContain(t('group.thisWeek'));
+    const row = container.querySelector('[data-session-id="wednesday"]');
+    expect(row?.closest('[role="group"]')?.getAttribute('aria-label')).toBe(
+      t('group.thisWeek'),
+    );
+  });
+});
diff --git a/packages/vscode-ide-companion/src/webview/components/SessionHistoryDropdown.tsx b/packages/vscode-ide-companion/src/webview/components/SessionHistoryDropdown.tsx
index 76ba044eaf8..cb5e93e86c4 100644
--- a/packages/vscode-ide-companion/src/webview/components/SessionHistoryDropdown.tsx
+++ b/packages/vscode-ide-companion/src/webview/components/SessionHistoryDropdown.tsx
@@ -33,6 +33,11 @@ function groupSessions(
   today.setHours(0, 0, 0, 0);
   const yesterday = new Date(today);
   yesterday.setDate(yesterday.getDate() - 1);
+  // Monday-first start of the current calendar week, derived from the same
+  // local day boundary as `today`/`yesterday`. Use setDate rather than
+  // millisecond arithmetic so a DST transition cannot shift the bucket edge.
+  const weekStart = new Date(today);
+  weekStart.setDate(today.getDate() - ((today.getDay() + 6) % 7));
   const groups = new Map<string, DaemonSessionSummary[]>([
     [t('group.today'), []],
     [t('group.yesterday'), []],
@@ -50,7 +55,7 @@ function groupSessions(
       if (day.getTime() === today.getTime()) label = t('group.today');
       else if (day.getTime() === yesterday.getTime()) {
         label = t('group.yesterday');
-      } else if (day.getTime() > today.getTime() - 7 * 86_400_000) {
+      } else if (day.getTime() >= weekStart.getTime()) {
         label = t('group.thisWeek');
       }
     }