diff --git a/open-isle-cli/src/main.js b/open-isle-cli/src/main.js
index e051776ff..c3e72a93a 100644
--- a/open-isle-cli/src/main.js
+++ b/open-isle-cli/src/main.js
@@ -3,4 +3,11 @@ import App from './App.vue'
 import router from './router'
 import './assets/global.css'
 
+// Configurable API domain and port
+export const API_DOMAIN =
+  process.env.VUE_APP_API_DOMAIN ||
+  `${window.location.protocol}//${window.location.hostname}`
+export const API_PORT = process.env.VUE_APP_API_PORT || window.location.port
+export const API_BASE_URL = API_PORT ? `${API_DOMAIN}:${API_PORT}` : API_DOMAIN
+
 createApp(App).use(router).mount('#app')
diff --git a/open-isle-cli/src/views/LoginPageView.vue b/open-isle-cli/src/views/LoginPageView.vue
index 37306c6ab..32c433c88 100644
--- a/open-isle-cli/src/views/LoginPageView.vue
+++ b/open-isle-cli/src/views/LoginPageView.vue
@@ -48,6 +48,7 @@
 </template>
 
 <script>
+import { API_BASE_URL } from '../main'
 export default {
   name: 'LoginPageView',
   data() {
@@ -59,7 +60,7 @@ export default {
   methods: {
     async submitLogin() {
       try {
-        const res = await fetch('/api/auth/login', {
+        const res = await fetch(`${API_BASE_URL}/api/auth/login`, {
           method: 'POST',
           headers: { 'Content-Type': 'application/json' },
           body: JSON.stringify({ username: this.username, password: this.password })
diff --git a/open-isle-cli/src/views/SignupPageView.vue b/open-isle-cli/src/views/SignupPageView.vue
index b71122d4d..b077be726 100644
--- a/open-isle-cli/src/views/SignupPageView.vue
+++ b/open-isle-cli/src/views/SignupPageView.vue
@@ -13,30 +13,36 @@
           <input
             class="signup-page-input-text"
             v-model="email"
+            @input="emailError = ''"
             type="text"
             placeholder="邮箱"
           >
         </div>
+        <div v-if="emailError" class="error-message">{{ emailError }}</div>
 
         <div class="signup-page-input">
           <i class="signup-page-input-icon fas fa-user"></i>
           <input
             class="signup-page-input-text"
             v-model="username"
+            @input="usernameError = ''"
             type="text"
             placeholder="用户名"
           >
         </div>
+        <div v-if="usernameError" class="error-message">{{ usernameError }}</div>
 
         <div class="signup-page-input">
           <i class="signup-page-input-icon fas fa-lock"></i>
           <input
             class="signup-page-input-text"
             v-model="password"
+            @input="passwordError = ''"
             type="password"
             placeholder="密码"
           >
         </div>
+        <div v-if="passwordError" class="error-message">{{ passwordError }}</div>
 
         <div class="signup-page-input">
           <i class="signup-page-input-icon fas fa-user"></i>
@@ -82,6 +88,7 @@
 </template>
 
 <script>
+import { API_BASE_URL } from '../main'
 export default {
   name: 'SignupPageView',
 
@@ -91,14 +98,36 @@ export default {
       email: '',
       username: '',
       password: '',
+      emailError: '',
+      usernameError: '',
+      passwordError: '',
       nickname: '',
       code: ''
     }
   },
   methods: {
+    clearErrors() {
+      this.emailError = ''
+      this.usernameError = ''
+      this.passwordError = ''
+    },
     async sendVerification() {
+      this.clearErrors()
+      const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/
+      if (!emailRegex.test(this.email)) {
+        this.emailError = '邮箱格式不正确'
+      }
+      if (!this.password || this.password.length < 6) {
+        this.passwordError = '密码至少6位'
+      }
+      if (!this.username) {
+        this.usernameError = '用户名不能为空'
+      }
+      if (this.emailError || this.passwordError || this.usernameError) {
+        return
+      }
       try {
-        const res = await fetch('http://localhost:8081/api/auth/register', {
+        const res = await fetch(`${API_BASE_URL}/api/auth/register`, {
           method: 'POST',
           headers: { 'Content-Type': 'application/json' },
           body: JSON.stringify({
@@ -111,6 +140,10 @@ export default {
         if (res.ok) {
           this.emailStep = 1
           alert('验证码已发送，请查看邮箱')
+        } else if (data.field) {
+          if (data.field === 'username') this.usernameError = data.error
+          if (data.field === 'email') this.emailError = data.error
+          if (data.field === 'password') this.passwordError = data.error
         } else {
           alert(data.error || '发送失败')
         }
@@ -120,7 +153,7 @@ export default {
     },
     async verifyCode() {
       try {
-        const res = await fetch('/api/auth/verify', {
+        const res = await fetch(`${API_BASE_URL}/api/auth/verify`, {
           method: 'POST',
           headers: { 'Content-Type': 'application/json' },
           body: JSON.stringify({ username: this.username, code: this.code })
@@ -272,4 +305,12 @@ export default {
 .signup-page-button-secondary-link {
   color: var(--primary-color);
 }
+
+.error-message {
+  color: red;
+  font-size: 14px;
+  width: calc(100% - 40px);
+  margin-top: -10px;
+  margin-bottom: 10px;
+}
 </style>
\ No newline at end of file
diff --git a/src/main/java/com/openisle/controller/GlobalExceptionHandler.java b/src/main/java/com/openisle/controller/GlobalExceptionHandler.java
index dcbd83e34..e093748e9 100644
--- a/src/main/java/com/openisle/controller/GlobalExceptionHandler.java
+++ b/src/main/java/com/openisle/controller/GlobalExceptionHandler.java
@@ -3,12 +3,19 @@ package com.openisle.controller;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.ExceptionHandler;
 import org.springframework.web.bind.annotation.RestControllerAdvice;
+import com.openisle.exception.FieldException;
 
 import java.util.Map;
 
 @RestControllerAdvice
 public class GlobalExceptionHandler {
 
+    @ExceptionHandler(FieldException.class)
+    public ResponseEntity<?> handleFieldException(FieldException ex) {
+        return ResponseEntity.badRequest()
+                .body(Map.of("error", ex.getMessage(), "field", ex.getField()));
+    }
+
     @ExceptionHandler(Exception.class)
     public ResponseEntity<?> handleException(Exception ex) {
         return ResponseEntity.badRequest().body(Map.of("error", ex.getMessage()));
diff --git a/src/main/java/com/openisle/exception/FieldException.java b/src/main/java/com/openisle/exception/FieldException.java
new file mode 100644
index 000000000..af56b3314
--- /dev/null
+++ b/src/main/java/com/openisle/exception/FieldException.java
@@ -0,0 +1,19 @@
+package com.openisle.exception;
+
+import lombok.Getter;
+
+/**
+ * Exception carrying a target field name. Useful for reporting
+ * validation errors to clients so they can display feedback near
+ * the appropriate input element.
+ */
+@Getter
+public class FieldException extends RuntimeException {
+    private final String field;
+
+    public FieldException(String field, String message) {
+        super(message);
+        this.field = field;
+    }
+}
+
diff --git a/src/main/java/com/openisle/service/PasswordValidator.java b/src/main/java/com/openisle/service/PasswordValidator.java
index 0f6c8518f..568b061f0 100644
--- a/src/main/java/com/openisle/service/PasswordValidator.java
+++ b/src/main/java/com/openisle/service/PasswordValidator.java
@@ -1,6 +1,7 @@
 package com.openisle.service;
 
 import com.openisle.model.PasswordStrength;
+import com.openisle.exception.FieldException;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.stereotype.Service;
 
@@ -14,7 +15,7 @@ public class PasswordValidator {
 
     public void validate(String password) {
         if (password == null || password.isEmpty()) {
-            throw new IllegalArgumentException("Password cannot be empty");
+            throw new FieldException("password", "Password cannot be empty");
         }
         switch (strength) {
             case MEDIUM:
@@ -31,34 +32,34 @@ public class PasswordValidator {
 
     private void checkLow(String password) {
         if (password.length() < 6) {
-            throw new IllegalArgumentException("Password must be at least 6 characters long");
+            throw new FieldException("password", "Password must be at least 6 characters long");
         }
     }
 
     private void checkMedium(String password) {
         if (password.length() < 8) {
-            throw new IllegalArgumentException("Password must be at least 8 characters long");
+            throw new FieldException("password", "Password must be at least 8 characters long");
         }
         if (!password.matches(".*[A-Za-z].*") || !password.matches(".*\\d.*")) {
-            throw new IllegalArgumentException("Password must contain letters and numbers");
+            throw new FieldException("password", "Password must contain letters and numbers");
         }
     }
 
     private void checkHigh(String password) {
         if (password.length() < 12) {
-            throw new IllegalArgumentException("Password must be at least 12 characters long");
+            throw new FieldException("password", "Password must be at least 12 characters long");
         }
         if (!password.matches(".*[A-Z].*")) {
-            throw new IllegalArgumentException("Password must contain uppercase letters");
+            throw new FieldException("password", "Password must contain uppercase letters");
         }
         if (!password.matches(".*[a-z].*")) {
-            throw new IllegalArgumentException("Password must contain lowercase letters");
+            throw new FieldException("password", "Password must contain lowercase letters");
         }
         if (!password.matches(".*\\d.*")) {
-            throw new IllegalArgumentException("Password must contain numbers");
+            throw new FieldException("password", "Password must contain numbers");
         }
         if (!password.matches(".*[^A-Za-z0-9].*")) {
-            throw new IllegalArgumentException("Password must contain special characters");
+            throw new FieldException("password", "Password must contain special characters");
         }
     }
 }
diff --git a/src/main/java/com/openisle/service/UserService.java b/src/main/java/com/openisle/service/UserService.java
index 330e78e16..5c50a8736 100644
--- a/src/main/java/com/openisle/service/UserService.java
+++ b/src/main/java/com/openisle/service/UserService.java
@@ -3,6 +3,7 @@ package com.openisle.service;
 import com.openisle.model.User;
 import com.openisle.model.Role;
 import com.openisle.service.PasswordValidator;
+import com.openisle.exception.FieldException;
 import com.openisle.repository.UserRepository;
 import lombok.RequiredArgsConstructor;
 import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
@@ -26,7 +27,7 @@ public class UserService {
         if (byUsername.isPresent()) {
             User u = byUsername.get();
             if (u.isVerified()) {                           // 已验证 → 直接拒绝
-                throw new IllegalStateException("User name already exists");
+                throw new FieldException("username", "User name already exists");
             }
             // 未验证 → 允许“重注册”：覆盖必要字段并重新发验证码
             u.setEmail(email);                              // 若不允许改邮箱可去掉
@@ -40,7 +41,7 @@ public class UserService {
         if (byEmail.isPresent()) {
             User u = byEmail.get();
             if (u.isVerified()) {                           // 已验证 → 直接拒绝
-                throw new IllegalStateException("User email already exists");
+                throw new FieldException("email", "User email already exists");
             }
             // 未验证 → 允许“重注册”
             u.setUsername(username);                        // 若不允许改用户名可去掉