diff --git a/app/api/auth/[...nextauth]/auth.config.ts b/app/api/auth/[...nextauth]/auth.config.ts
index 06b80ef1a..eceacb260 100644
--- a/app/api/auth/[...nextauth]/auth.config.ts
+++ b/app/api/auth/[...nextauth]/auth.config.ts
@@ -4,6 +4,16 @@ import CredentialsProvider from 'next-auth/providers/credentials';
 import { AuthService } from '@/services/auth.service';
 import { AuthSharingService } from '@/services/auth-sharing.service';
 
+export class NextAuthError extends Error {
+  constructor(
+    message: string,
+    public readonly code: string
+  ) {
+    super(message);
+    this.name = 'NextAuthError';
+  }
+}
+
 // Debug flag - set to true to enable detailed authentication logging
 const DEBUG_AUTH = true;
 
@@ -77,7 +87,7 @@ export const authOptions: NextAuthOptions = {
     error: '/auth/error',
   },
   callbacks: {
-    async signIn({ user, account, profile }) {
+    async signIn({ user, account, profile, email, credentials }) {
       if (account?.type === 'oauth') {
         try {
           // Log OAuth token state for debugging
@@ -141,25 +151,54 @@ export const authOptions: NextAuthOptions = {
 
           return true;
         } catch (error) {
-          // Log detailed error information
+          const errorType = error instanceof Error ? error.message : 'AuthenticationFailed';
           console.error('[Auth] Google OAuth error', {
-            error: error instanceof Error ? error.message : 'Unknown error',
+            error: errorType,
             errorType: error instanceof Error ? error.constructor.name : typeof error,
             stack: error instanceof Error ? error.stack : undefined,
             timestamp: new Date().toISOString(),
           });
 
-          // Preserve specific error messages for better debugging
-          if (error instanceof Error) {
-            throw new Error(error.message);
+          // Return false for OAuthAccountNotLinked to trigger consistent error flow
+          // This ensures the error is properly handled by the redirect callback
+          if (errorType === 'OAuthAccountNotLinked') {
+            return false;
           }
-          throw new Error('AuthenticationFailed');
+
+          throw new NextAuthError(errorType, 'OAUTH_ERROR');
         }
       }
 
       return true;
     },
 
+    async redirect({ url, baseUrl }) {
+      if (url.includes('/auth/error')) {
+        const urlObj = new URL(url, baseUrl);
+        const error = urlObj.searchParams.get('error');
+
+        // Map various OAuth error codes to OAuthAccountNotLinked
+        // This handles environment-specific error code variations
+        if (
+          error &&
+          (error === 'OAuthSignin' ||
+            error === 'OAuthCallback' ||
+            error === 'AccessDenied' ||
+            error === 'Callback' ||
+            error === 'OAuthCreateAccount' ||
+            error === 'AuthenticationFailed')
+        ) {
+          urlObj.searchParams.set('error', 'OAuthAccountNotLinked');
+        }
+
+        return urlObj.toString();
+      }
+
+      if (url.startsWith('/')) return `${baseUrl}${url}`;
+      if (new URL(url).origin === baseUrl) return url;
+      return baseUrl;
+    },
+
     async jwt({ token, user, account }) {
       if (account && user) {
         return {
diff --git a/app/auth/error/page.tsx b/app/auth/error/page.tsx
index 8f6169abd..8601696e8 100644
--- a/app/auth/error/page.tsx
+++ b/app/auth/error/page.tsx
@@ -1,13 +1,23 @@
 'use client';
 
-import { useSearchParams } from 'next/navigation';
-import { Suspense } from 'react';
+import { useEffect, Suspense } from 'react';
+import { useSearchParams, useRouter } from 'next/navigation';
 
 function ErrorContent() {
   const searchParams = useSearchParams();
-  const error = searchParams?.get('error');
+  const router = useRouter();
 
-  return null; // This page won't render anything, it just redirects
+  useEffect(() => {
+    const error = searchParams?.get('error');
+    const callbackUrl = searchParams?.get('callbackUrl') || '/';
+
+    const params = new URLSearchParams({ callbackUrl });
+    if (error) params.set('error', error);
+
+    router.replace(`/auth/signin?${params}`);
+  }, [searchParams, router]);
+
+  return null;
 }
 
 export default function ErrorPage() {
diff --git a/app/auth/signin/page.tsx b/app/auth/signin/page.tsx
index db6662475..fd175a85c 100644
--- a/app/auth/signin/page.tsx
+++ b/app/auth/signin/page.tsx
@@ -2,15 +2,40 @@
 
 import { useSearchParams } from 'next/navigation';
 import AuthContent from '@/components/Auth/AuthContent';
-import { useRouter } from 'next/navigation';
 import Image from 'next/image';
 import { Suspense } from 'react';
 
 function SignInContent() {
-  const router = useRouter();
   const searchParams = useSearchParams();
-  const error = searchParams?.get('error');
-  const callbackUrl = searchParams?.get('callbackUrl') || '/';
+  const errorCode = searchParams?.get('error');
+  let callbackUrl = searchParams?.get('callbackUrl') || '/';
+  //this is to help prevent redirecting issues when using the auth modal after an error occurs
+  if (callbackUrl.startsWith('http')) {
+    try {
+      const url = new URL(callbackUrl);
+      callbackUrl = url.pathname + url.search + url.hash;
+    } catch {}
+  }
+
+  if (callbackUrl.includes('/auth/')) {
+    callbackUrl = '/';
+  }
+
+  let error = null;
+  // Map various OAuth error codes to the account linking message
+  if (
+    errorCode === 'OAuthAccountNotLinked' ||
+    errorCode === 'OAuthSignin' ||
+    errorCode === 'OAuthCallback' ||
+    errorCode === 'AccessDenied' ||
+    errorCode === 'Callback' ||
+    errorCode === 'OAuthCreateAccount' ||
+    errorCode === 'AuthenticationFailed'
+  ) {
+    error = 'Enter email and password to login to your account.';
+  } else if (errorCode) {
+    error = 'An error occurred during authentication. Please try again.';
+  }
 
   return (
     <div className="min-h-screen flex flex-col items-center justify-center bg-gray-50 py-12 px-4 sm:px-6 lg:px-8">
@@ -35,17 +60,7 @@ function SignInContent() {
       </div>
 
       <div className="bg-white w-full max-w-md rounded-lg shadow-sm border border-gray-200 p-8">
-        {error && (
-          <div className="mb-4 p-3 bg-red-50 border border-red-200 rounded-lg">
-            <p className="text-sm text-red-600">{error}</p>
-          </div>
-        )}
-
-        <AuthContent
-          initialError={error}
-          onSuccess={() => router.push(callbackUrl)}
-          showHeader={false}
-        />
+        <AuthContent initialError={error} callbackUrl={callbackUrl} showHeader={false} />
       </div>
 
       <div className="mt-8 text-center text-sm text-gray-500">
diff --git a/components/Auth/AuthContent.tsx b/components/Auth/AuthContent.tsx
index da79bc052..a8c9d9891 100644
--- a/components/Auth/AuthContent.tsx
+++ b/components/Auth/AuthContent.tsx
@@ -14,6 +14,7 @@ interface AuthContentProps {
   initialScreen?: AuthScreen;
   showHeader?: boolean;
   modalView?: boolean;
+  callbackUrl?: string;
 }
 
 export default function AuthContent({
@@ -23,6 +24,7 @@ export default function AuthContent({
   initialScreen = 'SELECT_PROVIDER',
   showHeader = true,
   modalView = false,
+  callbackUrl,
 }: AuthContentProps) {
   const [screen, setScreen] = useState<AuthScreen>(initialScreen);
   const [email, setEmail] = useState('');
@@ -48,6 +50,7 @@ export default function AuthContent({
     setError,
     showHeader,
     modalView,
+    callbackUrl,
   };
 
   return (
diff --git a/components/Auth/screens/Login.tsx b/components/Auth/screens/Login.tsx
index aa3695b53..a71b8b7e7 100644
--- a/components/Auth/screens/Login.tsx
+++ b/components/Auth/screens/Login.tsx
@@ -14,6 +14,7 @@ interface Props extends BaseScreenProps {
   setIsLoading: (loading: boolean) => void;
   onSuccess?: () => void;
   modalView?: boolean;
+  callbackUrl?: string;
 }
 
 export default function Login({
@@ -27,6 +28,7 @@ export default function Login({
   onBack,
   onForgotPassword,
   modalView = false,
+  callbackUrl,
 }: Props) {
   const [password, setPassword] = useState('');
   const [showPassword, setShowPassword] = useState(false);
@@ -45,28 +47,23 @@ export default function Login({
     setError(null);
 
     try {
-      // This endpoint will return a CredentialsSignin error with no description.
-      // Currently we try to login with email and password + fetch the user's data separately,
-      // because the current endpoint only returns a token
-      // So, we show "Invalid email or password" error
-      const result = await signIn('credentials', {
-        email,
-        password,
-        redirect: false,
-      });
-
-      if (result?.error) {
-        setError('Invalid email or password');
+      if (callbackUrl) {
+        await signIn('credentials', { email, password, callbackUrl });
       } else {
-        setIsRedirecting(true); // Set redirecting state before navigation
-        onSuccess?.();
-        onClose();
+        const result = await signIn('credentials', { email, password, redirect: false });
+
+        if (result?.error) {
+          setError('Invalid email or password');
+        } else {
+          setIsRedirecting(true);
+          onSuccess?.();
+          onClose();
+        }
       }
-    } catch (err) {
+    } catch {
       setError('Login failed');
     } finally {
-      if (!isRedirecting) {
-        // Only reset loading if we're not redirecting
+      if (!isRedirecting && !callbackUrl) {
         setIsLoading(false);
       }
     }
diff --git a/components/Auth/screens/SelectProvider.tsx b/components/Auth/screens/SelectProvider.tsx
index a61310a5e..04d3fbd60 100644
--- a/components/Auth/screens/SelectProvider.tsx
+++ b/components/Auth/screens/SelectProvider.tsx
@@ -33,6 +33,20 @@ export default function SelectProvider({
   const emailInputRef = useAutoFocus<HTMLInputElement>(true);
   const { referralCode } = useReferral();
 
+  const getCallbackUrl = () => {
+    const searchParams = new URLSearchParams(globalThis.location.search);
+    return searchParams.get('callbackUrl') || '/';
+  };
+
+  const initiateGoogleSignIn = (callbackUrl: string) => {
+    const finalUrl = referralCode
+      ? new URL('/referral/join/apply-referral-code', globalThis.location.origin).toString() +
+        `?refr=${referralCode}&redirect=${encodeURIComponent(callbackUrl)}`
+      : callbackUrl;
+
+    signIn('google', { callbackUrl: finalUrl });
+  };
+
   const handleCheckAccount = async (e?: React.FormEvent) => {
     e?.preventDefault();
     if (!isValidEmail(email)) {
@@ -48,7 +62,7 @@ export default function SelectProvider({
 
       if (response.exists) {
         if (response.auth === 'google') {
-          signIn('google', { callbackUrl: '/' });
+          initiateGoogleSignIn(getCallbackUrl());
         } else if (response.is_verified) {
           onContinue();
         } else {
@@ -68,21 +82,7 @@ export default function SelectProvider({
     AnalyticsService.logEvent(LogEvent.AUTH_VIA_GOOGLE_INITIATED).catch((error) => {
       console.error('Analytics failed:', error);
     });
-
-    const searchParams = new URLSearchParams(window.location.search);
-    const originalCallbackUrl = searchParams.get('callbackUrl') || '/';
-
-    let finalCallbackUrl = originalCallbackUrl;
-
-    if (referralCode) {
-      // Create referral application URL with referral code and redirect as URL parameters
-      const referralUrl = new URL('/referral/join/apply-referral-code', window.location.origin);
-      referralUrl.searchParams.set('refr', referralCode);
-      referralUrl.searchParams.set('redirect', originalCallbackUrl);
-      finalCallbackUrl = referralUrl.toString();
-    }
-
-    signIn('google', { callbackUrl: finalCallbackUrl });
+    initiateGoogleSignIn(getCallbackUrl());
   };
 
   return (
diff --git a/services/auth.service.ts b/services/auth.service.ts
index 03b08f3f9..e3923f822 100644
--- a/services/auth.service.ts
+++ b/services/auth.service.ts
@@ -40,10 +40,21 @@ export class AuthService {
     try {
       return await ApiClient.post<User>(`${this.BASE_PATH}/auth/register/`, credentials);
     } catch (error: any) {
-      const { status } = error.message;
-      const data = error instanceof ApiError ? error.errors : {};
-      const errorMsg = Object.values(data as Record<string, string[]>)?.[0]?.[0];
-      throw new AuthError(errorMsg || 'Registration failed', status);
+      if (error instanceof ApiError) {
+        const data = error.errors || {};
+        const errorValues = Object.values(data as Record<string, string[]>)?.[0];
+        const errorMsg = Array.isArray(errorValues)
+          ? errorValues[0]
+          : typeof errorValues === 'string'
+            ? errorValues
+            : 'Registration failed';
+        throw new AuthError(errorMsg || 'Registration failed', error.status);
+      }
+
+      // Handle non-ApiError exceptions (network errors, etc.)
+      const errorMsg = error instanceof Error ? error.message : 'Registration failed';
+      console.error('[AuthService] Registration error:', error);
+      throw new AuthError(errorMsg, undefined);
     }
   }
 
@@ -171,16 +182,10 @@ export class AuthService {
           timestamp: new Date().toISOString(),
         });
 
-        switch (response.status) {
-          case 401:
-            throw new Error('AuthenticationFailed');
-          case 403:
-            throw new Error('AccessDenied');
-          case 409:
-            throw new Error('Verification');
-          default:
-            throw new Error('AuthenticationFailed');
+        if (response.status === 400 || response.status === 403 || response.status === 409) {
+          throw new Error('OAuthAccountNotLinked');
         }
+        throw new Error('AuthenticationFailed');
       }
 
       const data = await response.json();