diff --git a/server/routes/auth.ts b/server/routes/auth.ts
index 80371d1..fa37555 100644
--- a/server/routes/auth.ts
+++ b/server/routes/auth.ts
@@ -179,4 +179,68 @@ router.post('/change-password', asyncRoute(async (req, res) => {
   ok(res, '비밀번호가 변경되었습니다.');
 }));
 
+router.post('/diagnostics', asyncRoute(async (_req, res) => {
+  const tableResult = await query<{
+    users_table: string | null;
+    user_roles_table: string | null;
+    sessions_table: string | null;
+  }>(
+    `
+      SELECT
+        to_regclass('public.users')::text AS users_table,
+        to_regclass('public.user_roles')::text AS user_roles_table,
+        to_regclass('public.user_sessions')::text AS sessions_table
+    `,
+  );
+  const tables = tableResult.rows[0];
+  let users: Array<{
+    username: string;
+    enabled: boolean;
+    locked: boolean;
+    must_change_password: boolean;
+    password_hash_length: number;
+    roles: string[];
+  }> = [];
+  let userQueryError: string | undefined;
+
+  if (tables?.users_table && tables.user_roles_table) {
+    try {
+      const userResult = await query<{
+        username: string;
+        enabled: boolean;
+        locked: boolean;
+        must_change_password: boolean;
+        password_hash_length: number;
+        roles: string[];
+      }>(
+        `
+          SELECT
+            u.username,
+            u.enabled,
+            u.locked,
+            u.must_change_password,
+            length(u.password_hash) AS password_hash_length,
+            COALESCE(array_agg(ur.role) FILTER (WHERE ur.role IS NOT NULL), '{}') AS roles
+          FROM users u
+          LEFT JOIN user_roles ur ON ur.user_id = u.id
+          WHERE u.username IN ('admin', 'security', 'host', 'a', 's', 'h')
+          GROUP BY u.id
+          ORDER BY u.username
+        `,
+      );
+      users = userResult.rows;
+    } catch (error) {
+      userQueryError = error instanceof Error ? error.message : String(error);
+    }
+  }
+
+  ok(res, {
+    authApi: true,
+    checkedAt: new Date().toISOString(),
+    tables,
+    users,
+    userQueryError,
+  });
+}));
+
 export const authRouter = router;
diff --git a/server/routes/health.ts b/server/routes/health.ts
index b569f36..034ca97 100644
--- a/server/routes/health.ts
+++ b/server/routes/health.ts
@@ -10,6 +10,8 @@ healthRouter.get('/health', (_req, res) => {
   ok(res, {
     status: 'UP',
     service: 'acs-node',
+    build: 'auth-seed-20260714',
+    authApi: true,
   });
 });