diff --git a/app/(auth)/actions.ts b/app/(auth)/actions.ts
index 4c3bfd2dc..071f2e587 100644
--- a/app/(auth)/actions.ts
+++ b/app/(auth)/actions.ts
@@ -44,9 +44,10 @@ export const login = async (
       email: formData.get("email"),
       password: formData.get("password"),
     });
+    const normalizedEmail = validatedData.email.trim().toLowerCase();
 
     await signIn("credentials", {
-      email: validatedData.email,
+      email: normalizedEmail,
       password: validatedData.password,
       redirect: false,
     });
@@ -86,15 +87,16 @@ export const register = async (
       email: formData.get("email"),
       password: formData.get("password"),
     });
+    const normalizedEmail = validatedData.email.trim().toLowerCase();
 
-    const [user] = await getUser(validatedData.email);
+    const [user] = await getUser(normalizedEmail);
 
     if (user) {
       return { status: "user_exists" } as RegisterActionState;
     }
-    await createUser(validatedData.email, validatedData.password);
+    await createUser(normalizedEmail, validatedData.password);
     await signIn("credentials", {
-      email: validatedData.email,
+      email: normalizedEmail,
       password: validatedData.password,
       redirect: false,
     });
diff --git a/app/(auth)/auth.config.ts b/app/(auth)/auth.config.ts
index d3859dc2a..64bb6fb54 100644
--- a/app/(auth)/auth.config.ts
+++ b/app/(auth)/auth.config.ts
@@ -1,13 +1,10 @@
 import type { NextAuthConfig } from "next-auth";
-import { isIP } from "node:net";
 
 export function buildAuthConfig(authUrl?: string | null): NextAuthConfig {
   const resolvedAuthUrl = authUrl || process.env.AUTH_URL || "";
   const isSecure = resolvedAuthUrl.startsWith("https://");
-  const hostName = resolvedAuthUrl ? new URL(resolvedAuthUrl).hostname : undefined;
-  // Browsers may reject `Domain` cookies for IP hosts; keep them host-only in that case.
-  const cookieDomain =
-    hostName && hostName !== "localhost" && isIP(hostName) === 0 ? hostName : undefined;
+  // Use host-only cookies to avoid cross-domain login issues in multi-domain deployments.
+  const cookieDomain = undefined;
 
   return {
     trustHost: true,
diff --git a/app/(auth)/auth.ts b/app/(auth)/auth.ts
index 90db58565..e3be1c5ba 100644
--- a/app/(auth)/auth.ts
+++ b/app/(auth)/auth.ts
@@ -115,7 +115,14 @@ function createBaseProviders(googleClientId?: string, googleClientSecret?: strin
         }
 
         // 2. 邮箱密码登录逻辑
-        const { email, password } = credentials;
+        const email = String(credentials?.email || "").trim().toLowerCase();
+        const password = String(credentials?.password || "");
+
+        if (!email || !password) {
+          await compare(password || "", DUMMY_PASSWORD);
+          return null;
+        }
+
         const users = await getUser(email);
 
         if (users.length === 0) {
diff --git a/app/(auth)/login/page.tsx b/app/(auth)/login/page.tsx
index f0e3f2d3f..40c557a21 100644
--- a/app/(auth)/login/page.tsx
+++ b/app/(auth)/login/page.tsx
@@ -548,7 +548,7 @@ export default function Page() {
       {/* 钉钉登录 iframe 弹窗 / 多组织选择 */}
       {showDingTalkModal && (
         <div
-          className="fixed inset-0 bg-black/95 flex items-center justify-center z-50 backdrop-blur-sm"
+          className="fixed inset-0 bg-black/85 flex items-center justify-center z-50 backdrop-blur-sm"
           onClick={(e) => {
             if (e.target === e.currentTarget) closeDingTalkModal();
           }}
diff --git a/components/home/lovart-home.tsx b/components/home/lovart-home.tsx
index 4cb89c455..cd7b83eb4 100644
--- a/components/home/lovart-home.tsx
+++ b/components/home/lovart-home.tsx
@@ -594,7 +594,7 @@ export function LovartHome({
   };
 
   const handleEmailLogin = async () => {
-    const email = loginEmail.trim();
+    const email = loginEmail.trim().toLowerCase();
     if (!email || !loginPassword) {
       toast.error("请输入邮箱和密码");
       return;
@@ -608,7 +608,7 @@ export function LovartHome({
         redirect: false,
       });
 
-      if (result?.error) {
+      if (!result || result.error || result.ok === false) {
         toast.error("登录失败，请检查账号密码");
         return;
       }
@@ -1235,7 +1235,7 @@ export function LovartHome({
 
       {loginDialogOpen ? (
         <div
-          className="fixed inset-0 z-50 flex items-center justify-center bg-black/95 p-4 backdrop-blur-[1px]"
+          className="fixed inset-0 z-50 flex items-center justify-center bg-black/85 p-4 backdrop-blur-[1px]"
           onClick={() => setLoginDialogOpen(false)}
         >
           <div
diff --git a/lib/db/queries.ts b/lib/db/queries.ts
index ee845ada5..719d15a38 100644
--- a/lib/db/queries.ts
+++ b/lib/db/queries.ts
@@ -65,11 +65,16 @@ import { db } from "@/lib/db";
 
 
 export async function getUser(email: string): Promise<User[]> {
+  const normalizedEmail = email.trim().toLowerCase();
+  if (!normalizedEmail) {
+    return [];
+  }
+
   try {
     return await db
       .select()
       .from(user)
-      .where(eq(user.email, email))
+      .where(sql`lower(${user.email}) = ${normalizedEmail}`)
       .orderBy(desc(user.createdAt));
   } catch (_error) {
     throw new ChatSDKError(
@@ -81,9 +86,10 @@ export async function getUser(email: string): Promise<User[]> {
 
 export async function createUser(email: string, password: string) {
   const hashedPassword = generateHashedPassword(password);
+  const normalizedEmail = email.trim().toLowerCase();
 
   try {
-    return await db.insert(user).values({ email, password: hashedPassword });
+    return await db.insert(user).values({ email: normalizedEmail, password: hashedPassword });
   } catch (_error) {
     throw new ChatSDKError("bad_request:database", "Failed to create user");
   }