diff --git a/src/authkit-callback-route.spec.ts b/src/authkit-callback-route.spec.ts
index 530079e..5e5ca24 100644
--- a/src/authkit-callback-route.spec.ts
+++ b/src/authkit-callback-route.spec.ts
@@ -51,7 +51,7 @@ describe('authkit-callback-route', () => {
 
     beforeAll(() => {
       // Silence console.error during tests
-      jest.spyOn(console, 'error').mockImplementation(() => {});
+      jest.spyOn(console, 'error').mockImplementation(() => { });
     });
 
     beforeEach(async () => {
@@ -344,5 +344,37 @@ describe('authkit-callback-route', () => {
       // Should still redirect correctly
       expect(response.headers.get('Location')).toContain('/old-path');
     });
+
+    it('should return error and set no cookies when onSuccess throws', async () => {
+      // Mock authenticate success
+      jest.mocked(workos.userManagement.authenticateWithCode).mockResolvedValue(mockAuthResponse);
+
+      // Prepare request with code + state
+      request.nextUrl.searchParams.set('code', 'test-code');
+      request.nextUrl.searchParams.set('state', 'dummy-state');
+
+      // Make onSuccess throw intentionally
+      const onSuccess = jest.fn(() => {
+        throw new Error('onSuccess failed');
+      });
+
+      const handler = handleAuth({ onSuccess });
+
+      const response = await handler(request);
+
+      // 1. Status must be error (400, 500 — depends on your handler)
+      expect(response.status).toBeGreaterThanOrEqual(400);
+
+      // 2. Response should contain error message
+      const body = await response.json();
+      expect(body.error).toBeDefined();
+      expect(body.error.message).toBe('Something went wrong');
+
+      // 3. No cookies should be set
+      // NextResponse stores cookies in headers.getSetCookie()
+
+      const nextCookies = await cookies();
+      expect(nextCookies.getAll()).toHaveLength(0);
+    });
   });
 });
diff --git a/src/authkit-callback-route.ts b/src/authkit-callback-route.ts
index daf4e89..3e7a15c 100644
--- a/src/authkit-callback-route.ts
+++ b/src/authkit-callback-route.ts
@@ -1,7 +1,7 @@
 import { NextRequest } from 'next/server';
 import { WORKOS_CLIENT_ID } from './env-variables.js';
 import { HandleAuthOptions } from './interfaces.js';
-import { saveSession } from './session.js';
+import { deleteSession, saveSession } from './session.js';
 import { errorResponseWithFallback, redirectWithFallback, setCachePreventionHeaders } from './utils.js';
 import { getWorkOS } from './workos.js';
 
@@ -102,16 +102,21 @@ export function handleAuth(options: HandleAuthOptions = {}) {
         await saveSession({ accessToken, refreshToken, user, impersonator }, request);
 
         if (onSuccess) {
-          await onSuccess({
-            accessToken,
-            refreshToken,
-            user,
-            impersonator,
-            oauthTokens,
-            authenticationMethod,
-            organizationId,
-            state: customState,
-          });
+          try {
+            await onSuccess({
+              accessToken,
+              refreshToken,
+              user,
+              impersonator,
+              oauthTokens,
+              authenticationMethod,
+              organizationId,
+              state: customState,
+            });
+          } catch (error) {
+            deleteSession();
+            throw error;
+          }
         }
 
         return response;
diff --git a/src/session.ts b/src/session.ts
index 9513891..3966e47 100644
--- a/src/session.ts
+++ b/src/session.ts
@@ -625,4 +625,10 @@ export async function saveSession(
   nextCookies.set(cookieName, encryptedSession, getCookieOptions(url));
 }
 
+export async function deleteSession() {
+  const nextCookies = await cookies();
+  const cookieName = WORKOS_COOKIE_NAME || 'wos-session';
+  nextCookies.delete(cookieName);
+}
+
 export { encryptSession, refreshSession, updateSession, updateSessionMiddleware, withAuth };