diff --git a/ui/desktop/src/__tests__/sessions.test.ts b/ui/desktop/src/__tests__/sessions.test.ts
new file mode 100644
index 0000000000..80631af718
--- /dev/null
+++ b/ui/desktop/src/__tests__/sessions.test.ts
@@ -0,0 +1,108 @@
+import { describe, it, expect } from 'vitest';
+import { shouldShowNewChatTitle } from '../sessions';
+import type { Session } from '../api';
+
+// Helper to build a minimal Session object for testing.
+function makeSession(overrides: Partial<Session> = {}): Session {
+  return {
+    id: 'sess-1',
+    name: 'untitled',
+    message_count: 0,
+    created_at: new Date().toISOString(),
+    updated_at: new Date().toISOString(),
+    working_dir: '/tmp',
+    extension_data: { active: [], installed: [] },
+    ...overrides,
+  };
+}
+
+describe('shouldShowNewChatTitle', () => {
+  it('returns true for an empty session without a user-set name', () => {
+    const session = makeSession({ message_count: 0, user_set_name: false });
+    expect(shouldShowNewChatTitle(session)).toBe(true);
+  });
+
+  it('returns false when the session has messages', () => {
+    const session = makeSession({ message_count: 3, user_set_name: false });
+    expect(shouldShowNewChatTitle(session)).toBe(false);
+  });
+
+  it('returns false when the user has set a custom name', () => {
+    const session = makeSession({ message_count: 0, user_set_name: true });
+    expect(shouldShowNewChatTitle(session)).toBe(false);
+  });
+
+  it('returns false when the session has a recipe', () => {
+    const session = makeSession({
+      message_count: 0,
+      user_set_name: false,
+      recipe: { title: 'Recipe', steps: [] } as unknown as Session['recipe'],
+    });
+    expect(shouldShowNewChatTitle(session)).toBe(false);
+  });
+});
+
+describe('session reuse scoping (fix for #7601)', () => {
+  // Simulates the core logic extracted from handleNewChat in useNavigationSessions.ts.
+  // Before the fix: `sessions.find(s => shouldShowNewChatTitle(s))` picked the
+  // first global empty session regardless of which window called it.
+  // After the fix: only the current window's activeSessionId is considered.
+  function findReusableSession(
+    sessions: Session[],
+    activeSessionId: string | undefined
+  ): Session | undefined {
+    const currentActive = activeSessionId
+      ? sessions.find((s) => s.id === activeSessionId)
+      : undefined;
+    if (currentActive && shouldShowNewChatTitle(currentActive)) {
+      return currentActive;
+    }
+    return undefined;
+  }
+
+  const emptySessionA = makeSession({ id: 'empty-a', message_count: 0, user_set_name: false });
+  const emptySessionB = makeSession({ id: 'empty-b', message_count: 0, user_set_name: false });
+  const usedSession = makeSession({ id: 'used-c', message_count: 5, user_set_name: true });
+
+  const allSessions = [emptySessionA, emptySessionB, usedSession];
+
+  it('window A only reuses its own active empty session, not window B\'s', () => {
+    // Window A has emptySessionA active, Window B has emptySessionB active.
+    // Under the old logic, both would grab emptySessionA (the first in the list).
+    const windowAResult = findReusableSession(allSessions, 'empty-a');
+    const windowBResult = findReusableSession(allSessions, 'empty-b');
+
+    expect(windowAResult?.id).toBe('empty-a');
+    expect(windowBResult?.id).toBe('empty-b');
+    // They never collide on the same session.
+    expect(windowAResult?.id).not.toBe(windowBResult?.id);
+  });
+
+  it('does not reuse a session that has messages even if it is active', () => {
+    const result = findReusableSession(allSessions, 'used-c');
+    expect(result).toBeUndefined();
+  });
+
+  it('returns undefined when there is no active session id', () => {
+    const result = findReusableSession(allSessions, undefined);
+    expect(result).toBeUndefined();
+  });
+
+  it('returns undefined when the active session id is not in the list', () => {
+    const result = findReusableSession(allSessions, 'nonexistent');
+    expect(result).toBeUndefined();
+  });
+
+  it('demonstrates the old bug: global find would give same session to both windows', () => {
+    // Old logic (before fix) - both windows get the same session.
+    const oldLogicFind = (sessions: Session[]) =>
+      sessions.find((s) => shouldShowNewChatTitle(s));
+
+    const windowAOld = oldLogicFind(allSessions);
+    const windowBOld = oldLogicFind(allSessions);
+
+    // Both windows would grab the exact same session - the bug.
+    expect(windowAOld?.id).toBe(windowBOld?.id);
+    expect(windowAOld?.id).toBe('empty-a');
+  });
+});
diff --git a/ui/desktop/src/hooks/useNavigationSessions.ts b/ui/desktop/src/hooks/useNavigationSessions.ts
index 1bc49e525b..be99d1a6ca 100644
--- a/ui/desktop/src/hooks/useNavigationSessions.ts
+++ b/ui/desktop/src/hooks/useNavigationSessions.ts
@@ -159,10 +159,16 @@ export function useNavigationSessions(options: UseNavigationSessionsOptions = {}
   const handleNewChat = useCallback(async () => {
     if (isCreatingSessionRef.current) return;
 
-    const emptyNewSession = sessionsRef.current.find((s) => shouldShowNewChatTitle(s));
+    // Only reuse the current window's own active session if it is empty.
+    // Previously this grabbed the first empty session globally, which caused
+    // multiple windows to claim the same empty session after a restart/upgrade.
+    const currentActiveSession = activeSessionId
+      ? sessionsRef.current.find((s) => s.id === activeSessionId)
+      : undefined;
+    const canReuseActive = currentActiveSession && shouldShowNewChatTitle(currentActiveSession);
 
-    if (emptyNewSession) {
-      resumeSession(emptyNewSession, setView);
+    if (canReuseActive) {
+      resumeSession(currentActiveSession, setView);
     } else {
       isCreatingSessionRef.current = true;
       try {
@@ -176,7 +182,7 @@ export function useNavigationSessions(options: UseNavigationSessionsOptions = {}
       }
     }
     onNavigate?.();
-  }, [setView, onNavigate, extensionsList]);
+  }, [setView, onNavigate, extensionsList, activeSessionId]);
 
   const handleSessionClick = useCallback(
     (sessionId: string) => {