diff --git a/backend/internal/service/auth_service.go b/backend/internal/service/auth_service.go
index 85772e75..5a5ca03d 100644
--- a/backend/internal/service/auth_service.go
+++ b/backend/internal/service/auth_service.go
@@ -82,14 +82,18 @@ func (s *AuthService) RegisterWithVerification(ctx context.Context, email, passw
 
 	// 检查是否需要邮件验证
 	if s.settingService != nil && s.settingService.IsEmailVerifyEnabled(ctx) {
+		// 如果邮件验证已开启但邮件服务未配置，拒绝注册
+		// 这是一个配置错误，不应该允许绕过验证
+		if s.emailService == nil {
+			log.Println("[Auth] Email verification enabled but email service not configured, rejecting registration")
+			return "", nil, ErrServiceUnavailable
+		}
 		if verifyCode == "" {
 			return "", nil, ErrEmailVerifyRequired
 		}
 		// 验证邮箱验证码
-		if s.emailService != nil {
-			if err := s.emailService.VerifyCode(ctx, email, verifyCode); err != nil {
-				return "", nil, fmt.Errorf("verify code: %w", err)
-			}
+		if err := s.emailService.VerifyCode(ctx, email, verifyCode); err != nil {
+			return "", nil, fmt.Errorf("verify code: %w", err)
 		}
 	}
 
@@ -336,6 +340,11 @@ func (s *AuthService) ValidateToken(tokenString string) (*JWTClaims, error) {
 
 	if err != nil {
 		if errors.Is(err, jwt.ErrTokenExpired) {
+			// token 过期但仍返回 claims（用于 RefreshToken 等场景）
+			// jwt-go 在解析时即使遇到过期错误，token.Claims 仍会被填充
+			if claims, ok := token.Claims.(*JWTClaims); ok {
+				return claims, ErrTokenExpired
+			}
 			return nil, ErrTokenExpired
 		}
 		return nil, ErrInvalidToken
diff --git a/backend/internal/service/auth_service_register_test.go b/backend/internal/service/auth_service_register_test.go
index cd6e2808..a31267ab 100644
--- a/backend/internal/service/auth_service_register_test.go
+++ b/backend/internal/service/auth_service_register_test.go
@@ -113,13 +113,27 @@ func TestAuthService_Register_Disabled(t *testing.T) {
 	require.ErrorIs(t, err, ErrRegDisabled)
 }
 
-func TestAuthService_Register_EmailVerifyRequired(t *testing.T) {
+func TestAuthService_Register_EmailVerifyEnabledButServiceNotConfigured(t *testing.T) {
 	repo := &userRepoStub{}
+	// 邮件验证开启但 emailCache 为 nil（emailService 未配置）
 	service := newAuthService(repo, map[string]string{
 		SettingKeyRegistrationEnabled: "true",
 		SettingKeyEmailVerifyEnabled:  "true",
 	}, nil)
 
+	// 应返回服务不可用错误，而不是允许绕过验证
+	_, _, err := service.RegisterWithVerification(context.Background(), "user@test.com", "password", "any-code")
+	require.ErrorIs(t, err, ErrServiceUnavailable)
+}
+
+func TestAuthService_Register_EmailVerifyRequired(t *testing.T) {
+	repo := &userRepoStub{}
+	cache := &emailCacheStub{} // 配置 emailService
+	service := newAuthService(repo, map[string]string{
+		SettingKeyRegistrationEnabled: "true",
+		SettingKeyEmailVerifyEnabled:  "true",
+	}, cache)
+
 	_, _, err := service.RegisterWithVerification(context.Background(), "user@test.com", "password", "")
 	require.ErrorIs(t, err, ErrEmailVerifyRequired)
 }
@@ -180,3 +194,63 @@ func TestAuthService_Register_Success(t *testing.T) {
 	require.Len(t, repo.created, 1)
 	require.True(t, user.CheckPassword("password"))
 }
+
+func TestAuthService_ValidateToken_ExpiredReturnsClaimsWithError(t *testing.T) {
+	repo := &userRepoStub{}
+	service := newAuthService(repo, nil, nil)
+
+	// 创建用户并生成 token
+	user := &User{
+		ID:           1,
+		Email:        "test@test.com",
+		Role:         RoleUser,
+		Status:       StatusActive,
+		TokenVersion: 1,
+	}
+	token, err := service.GenerateToken(user)
+	require.NoError(t, err)
+
+	// 验证有效 token
+	claims, err := service.ValidateToken(token)
+	require.NoError(t, err)
+	require.NotNil(t, claims)
+	require.Equal(t, int64(1), claims.UserID)
+
+	// 模拟过期 token（通过创建一个过期很久的 token）
+	service.cfg.JWT.ExpireHour = -1 // 设置为负数使 token 立即过期
+	expiredToken, err := service.GenerateToken(user)
+	require.NoError(t, err)
+	service.cfg.JWT.ExpireHour = 1 // 恢复
+
+	// 验证过期 token 应返回 claims 和 ErrTokenExpired
+	claims, err = service.ValidateToken(expiredToken)
+	require.ErrorIs(t, err, ErrTokenExpired)
+	require.NotNil(t, claims, "claims should not be nil when token is expired")
+	require.Equal(t, int64(1), claims.UserID)
+	require.Equal(t, "test@test.com", claims.Email)
+}
+
+func TestAuthService_RefreshToken_ExpiredTokenNoPanic(t *testing.T) {
+	user := &User{
+		ID:           1,
+		Email:        "test@test.com",
+		Role:         RoleUser,
+		Status:       StatusActive,
+		TokenVersion: 1,
+	}
+	repo := &userRepoStub{user: user}
+	service := newAuthService(repo, nil, nil)
+
+	// 创建过期 token
+	service.cfg.JWT.ExpireHour = -1
+	expiredToken, err := service.GenerateToken(user)
+	require.NoError(t, err)
+	service.cfg.JWT.ExpireHour = 1
+
+	// RefreshToken 使用过期 token 不应 panic
+	require.NotPanics(t, func() {
+		newToken, err := service.RefreshToken(context.Background(), expiredToken)
+		require.NoError(t, err)
+		require.NotEmpty(t, newToken)
+	})
+}