fix(clerk-js): Detect if user is signed in already

packages/clerk-js/src/ui/components/SignIn/SignInStart.tsx

@@ -181,6 +181,18 @@ function SignInStartInternal(): JSX.Element {
     setShouldAutofocus(true);
   };
 
+  /**
+   * Redirect to account switcher if user already has active sessions in multi-session mode
+   */
+  useEffect(() => {
+    const hasActiveSessions = (clerk.client?.signedInSessions?.length ?? 0) > 0;
+    const isMultiSessionMode = !authConfig.singleSessionMode;
+
+    if (hasActiveSessions && isMultiSessionMode) {
+      void navigate('choose');
+    }
+  }, [clerk.client?.signedInSessions, authConfig.singleSessionMode, navigate]);
+
   // switch to the phone input (if available) if a "+" is entered
   // (either by the browser or the user)
   // this does not work in chrome as it does not fire the change event and the value is

packages/clerk-js/src/ui/components/SignIn/__tests__/SignInStart.test.tsx

@@ -590,4 +590,111 @@ describe('SignInStart', () => {
       );
     });
   });
+
+  describe('Active session redirect', () => {
+    describe('multi-session mode', () => {
+      it('redirects to /choose when user has active sessions', async () => {
+        const { wrapper, fixtures } = await createFixtures(f => {
+          f.withEmailAddress();
+          f.withMultiSessionMode();
+          f.withUser({
+            email_addresses: ['[email protected]'],
+          });
+        });
+
+        fixtures.clerk.client.signedInSessions = [
+          {
+            id: 'sess_123',
+            user: fixtures.clerk.user,
+            status: 'active',
+          } as any,
+        ];
+
+        render(<SignInStart />, { wrapper });
+
+        await waitFor(() => {
+          expect(fixtures.router.navigate).toHaveBeenCalledWith('choose');
+        });
+      });
+
+      it('redirects to /choose when user has multiple active sessions', async () => {
+        const { wrapper, fixtures } = await createFixtures(f => {
+          f.withEmailAddress();
+          f.withMultiSessionMode();
+          f.withUser({
+            email_addresses: ['[email protected]'],
+          });
+        });
+
+        fixtures.clerk.client.signedInSessions = [
+          {
+            id: 'sess_123',
+            user: fixtures.clerk.user,
+            status: 'active',
+          } as any,
+          {
+            id: 'sess_456',
+            user: { id: 'user_456' },
+            status: 'active',
+          } as any,
+        ];
+
+        render(<SignInStart />, { wrapper });
+
+        await waitFor(() => {
+          expect(fixtures.router.navigate).toHaveBeenCalledWith('choose');
+        });
+      });
+
+      it('does NOT redirect when user has no active sessions', async () => {
+        const { wrapper, fixtures } = await createFixtures(f => {
+          f.withEmailAddress();
+          f.withMultiSessionMode();
+        });
+
+        fixtures.clerk.client.signedInSessions = [];
+
+        render(<SignInStart />, { wrapper });
+
+        await waitFor(
+          () => {
+            expect(fixtures.router.navigate).not.toHaveBeenCalledWith('choose');
+          },
+          { timeout: 100 },
+        );
+
+        screen.getByText(/email address/i);
+      });
+    });
+
+    describe('single-session mode', () => {
+      it('does NOT redirect to /choose when user has active session in single-session mode', async () => {
+        const { wrapper, fixtures } = await createFixtures(f => {
+          f.withEmailAddress();
+          f.withUser({
+            email_addresses: ['[email protected]'],
+          });
+        });
+
+        fixtures.clerk.client.signedInSessions = [
+          {
+            id: 'sess_123',
+            user: fixtures.clerk.user,
+            status: 'active',
+          } as any,
+        ];
+
+        fixtures.environment.authConfig.singleSessionMode = true;
+
+        render(<SignInStart />, { wrapper });
+
+        await waitFor(
+          () => {
+            expect(fixtures.router.navigate).not.toHaveBeenCalledWith('choose');
+          },
+          { timeout: 100 },
+        );
+      });
+    });
+  });
 });