Fix GitHub OAuth login for migrated users (#2620)

Co-authored-by: Cursor Agent <cursoragent@cursor.com>

src/components/user/dropdown-menu.tsx

@@ -60,7 +60,7 @@ export function UserDropdownMenu({ children }: Props) {
 		});
 	}
 
-	if (!session) return null;
+	if (!session?.user) return null;
 
 	return (
 		<DropdownMenu>

src/integrations/auth/config.ts

@@ -1,4 +1,5 @@
 import { BetterAuthError } from "@better-auth/core/error";
+import { and, eq, or } from "drizzle-orm";
 import { passkey } from "@better-auth/passkey";
 import { drizzleAdapter } from "better-auth/adapters/drizzle";
 import { betterAuth } from "better-auth/minimal";
@@ -161,12 +162,44 @@ const getAuthConfig = () => {
 				// biome-ignore lint/style/noNonNullAssertion: enabled check ensures these are not null
 				clientSecret: env.GITHUB_CLIENT_SECRET!,
 				mapProfileToUser: async (profile) => {
+					const login = profile.login ?? String(profile.id);
+					const normalizedLogin = toUsername(login);
+					const [legacyAccount] = await db
+						.select({
+							accountId: schema.account.accountId,
+							email: schema.user.email,
+							emailVerified: schema.user.emailVerified,
+							username: schema.user.username,
+							displayUsername: schema.user.displayUsername,
+						})
+						.from(schema.account)
+						.innerJoin(schema.user, eq(schema.account.userId, schema.user.id))
+						.where(
+							and(
+								eq(schema.account.providerId, "github"),
+								or(eq(schema.user.username, normalizedLogin), eq(schema.user.displayUsername, login)),
+							),
+						)
+						.limit(1);
+
+					if (legacyAccount) {
+						return {
+							id: legacyAccount.accountId,
+							name: profile.name,
+							email: legacyAccount.email,
+							image: profile.avatar_url,
+							username: legacyAccount.username,
+							displayUsername: legacyAccount.displayUsername,
+							emailVerified: legacyAccount.emailVerified,
+						};
+					}
+
 					return {
 						name: profile.name,
 						email: profile.email,
 						image: profile.avatar_url,
-						username: profile.login,
-						displayUsername: profile.login,
+						username: normalizedLogin,
+						displayUsername: login,
 						emailVerified: true,
 					};
 				},