diff --git a/app/api/auth/[...nextauth]/route.ts b/app/api/auth/[...nextauth]/route.ts
index 1adb544..68d5be1 100644
--- a/app/api/auth/[...nextauth]/route.ts
+++ b/app/api/auth/[...nextauth]/route.ts
@@ -18,59 +18,72 @@ const authOptions: NextAuthOptions = {
   ],
   adapter: FirestoreAdapter(adminDb),
   callbacks: {
-    async signIn({ user, account }) {
-      const userEmail = user.email;
-      const provider = account.provider;
+  async signIn({ user, account }) {
+    const userEmail = user.email;
+    const provider = account.provider;
 
-      if (!userEmail || !provider) return false;
+    if (!userEmail || !provider) return false;
 
-      try {
-        const userDocRef = adminDb.collection("users").doc(userEmail);
-        const userDoc = await userDocRef.get();
+    try {
+      const userDocRef = adminDb.collection("users").doc(userEmail);
+      const userDoc = await userDocRef.get();
 
-        if (userDoc.exists) {
-          const userData = userDoc.data();
+      if (userDoc.exists) {
+        const userData = userDoc.data();
 
-          if (!userData) {
-            console.error("User data not found");
-            return false;
-          }
-
-          console.log("Existing user signing in:", userData);
+        if (!userData) {
+          console.error("User data not found");
+          return false;
+        }
 
-          if (userData.provider && userData.provider !== provider) {
-            const linkedProviders = userData.linkedProviders || [];
-            if (!linkedProviders.includes(provider)) {
-              linkedProviders.push(provider);
-              await userDocRef.update({ linkedProviders });
-            }
-          } else if (!userData.provider) {
-            await userDocRef.update({ provider });
-          }
+        console.log("Existing user signing in:", userData);
 
+        // Check if provider is already linked
+        if (userData.linkedProviders && userData.linkedProviders.includes(provider)) {
           return true;
-        } else {
-          console.log("New user signing up:", { email: userEmail, provider });
-
-          await userDocRef.set({
-            email: userEmail,
-            plan: "free",
-            requestCount: 0,
-            provider,
-            linkedProviders: [provider],
-          });
+        }
 
+        // Link provider to existing account
+        if (userData.provider && userData.provider !== provider) {
+          const linkedProviders = userData.linkedProviders || [];
+          if (!linkedProviders.includes(provider)) {
+            linkedProviders.push(provider);
+            await userDocRef.update({ linkedProviders });
+          }
           return true;
         }
-      } catch (error) {
-        if (error.code === 'auth/invalid-email') {
-          console.error('Invalid email:', error);
-        } else {
-          console.error('Sign-in error:', error);
+
+        // Handle new provider for existing user without provider
+        if (!userData.provider) {
+          await userDocRef.update({ provider, linkedProviders: [provider] });
+          return true;
         }
+
+        // If none of the above conditions are met, return error
+        console.error("OAuthAccountNotLinked error");
         return false;
+      } else {
+        // Create new user document
+        console.log("New user signing up:", { email: userEmail, provider });
+        await userDocRef.set({
+          email: userEmail,
+          plan: "free",
+          requestCount: 0,
+          provider,
+          linkedProviders: [provider],
+        });
+        return true;
       }
-    },
+    } catch (error) {
+      if (error.code === 'auth/invalid-email') {
+        console.error('Invalid email:', error);
+      } else {
+        console.error('Sign-in error:', error);
+      }
+      return false;
+    }
+  },
+
     async session({ session, user }) {
       console.log("Session data:", session);
       session.user.id = user.id;