diff --git a/web-api/ruoyi-admin/src/main/java/com/ruoyi/api/PortalVideoController.java b/web-api/ruoyi-admin/src/main/java/com/ruoyi/api/PortalVideoController.java
index 052ae25..d0f2646 100644
--- a/web-api/ruoyi-admin/src/main/java/com/ruoyi/api/PortalVideoController.java
+++ b/web-api/ruoyi-admin/src/main/java/com/ruoyi/api/PortalVideoController.java
@@ -109,6 +109,16 @@ public class PortalVideoController extends BaseController {
         }
     }
 
+    /** 二级部门 sys_dept.model_parm 中 JSON 数组第一项的 value（与 parseModelParmJson 规则一致）。 */
+    private String resolveFirstModelValueFromModelParm(Long aiUserId) {
+        String json = byteDeptApiKeyService.resolveSecondLevelModelParm(aiUserId);
+        List<PortalVideoProperties.ModelOption> list = parseModelParmJson(json);
+        if (list == null || list.isEmpty()) {
+            return null;
+        }
+        return list.get(0).getValue();
+    }
+
     private static boolean isModelInOptions(String modelId, List<PortalVideoProperties.ModelOption> options) {
         if (modelId == null || modelId.isEmpty() || options == null) {
             return false;
@@ -523,6 +533,10 @@ public class PortalVideoController extends BaseController {
         Long secondDeptId = byteDeptApiKeyService.resolveSecondLevelDeptId(uid);
         List<PortalVideoProperties.ModelOption> models = loadModelOptionsForAiUser(uid, secondDeptId);
         PortalVideoProperties.Defaults defs = portalVideoProperties.resolveEffectiveDefaults(secondDeptId);
+        String modelFromDeptParm = resolveFirstModelValueFromModelParm(uid);
+        if (StringUtils.isNotEmpty(modelFromDeptParm)) {
+            defs.setModel(modelFromDeptParm);
+        }
         alignDefaultsModelToOptions(defs, models);
         Map<String, Object> data = new LinkedHashMap<>();
         data.put("defaults", defs);
diff --git a/web-api/ruoyi-system/src/main/java/com/ruoyi/ai/mapper/AiUserMapper.java b/web-api/ruoyi-system/src/main/java/com/ruoyi/ai/mapper/AiUserMapper.java
index d5c8c74..5a2fadc 100644
--- a/web-api/ruoyi-system/src/main/java/com/ruoyi/ai/mapper/AiUserMapper.java
+++ b/web-api/ruoyi-system/src/main/java/com/ruoyi/ai/mapper/AiUserMapper.java
@@ -26,6 +26,11 @@ public interface AiUserMapper extends BaseMapper<AiUser> {
 
     int countAiUserByDeptId(@Param("deptId") Long deptId);
 
+    /**
+     * 部门下启用中的 AI 用户（未删除且 status=0）
+     */
+    int countNormalAiUsersByDeptId(@Param("deptId") Long deptId, @Param("excludeUserId") Long excludeUserId);
+
     @Update("update ai_user set dept_id = #{deptId}, update_time = sysdate() where id = #{userId}")
     int updateAiUserDeptId(@Param("userId") Long userId, @Param("deptId") Long deptId);
 }
diff --git a/web-api/ruoyi-system/src/main/java/com/ruoyi/ai/service/impl/AiUserServiceImpl.java b/web-api/ruoyi-system/src/main/java/com/ruoyi/ai/service/impl/AiUserServiceImpl.java
index 1b12ca5..1f96e9e 100644
--- a/web-api/ruoyi-system/src/main/java/com/ruoyi/ai/service/impl/AiUserServiceImpl.java
+++ b/web-api/ruoyi-system/src/main/java/com/ruoyi/ai/service/impl/AiUserServiceImpl.java
@@ -20,8 +20,10 @@ import com.ruoyi.common.core.domain.model.RegisterAiUserBody;
 import com.ruoyi.common.exception.ServiceException;
 import com.ruoyi.common.utils.*;
 import com.ruoyi.common.utils.ip.IpUtils;
+import com.ruoyi.common.core.domain.entity.SysDept;
 import com.ruoyi.system.domain.SysConfig;
 import com.ruoyi.system.mapper.SysConfigMapper;
+import com.ruoyi.system.service.ISysDeptService;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
@@ -65,6 +67,29 @@ public class AiUserServiceImpl implements IAiUserService {
     @Autowired
     private AiRechargeMapper aiRechargeMapper;
 
+    @Autowired
+    private ISysDeptService deptService;
+
+    /**
+     * 校验部门下启用中 AI 账号未超过 max_user_count（为空或≤0 表示不限制）
+     */
+    private void assertDeptAiUserWithinLimit(Long deptId, Long excludeUserId) {
+        if (deptId == null) {
+            return;
+        }
+        SysDept dept = deptService.selectDeptById(deptId);
+        if (dept == null) {
+            return;
+        }
+        Integer max = dept.getMaxUserCount();
+        if (max == null || max <= 0) {
+            return;
+        }
+        int others = aiUserMapper.countNormalAiUsersByDeptId(deptId, excludeUserId);
+        if (others + 1 > max) {
+            throw new ServiceException("团队人数已经超过上限", HttpStatus.BAD_REQUEST);
+        }
+    }
 
     /**
      * 查询ai-用户信息
@@ -133,6 +158,9 @@ public class AiUserServiceImpl implements IAiUserService {
         if (aiUser.getStatus() == null) {
             aiUser.setStatus(0);
         }
+        if (aiUser.getStatus() == 0) {
+            assertDeptAiUserWithinLimit(aiUser.getDeptId(), null);
+        }
         aiUser.setDelFlag("0");
         aiUser.setCreateBy(SecurityUtils.getUsername());
         aiUser.setCreateTime(DateUtils.getNowDate());
@@ -147,6 +175,14 @@ public class AiUserServiceImpl implements IAiUserService {
      */
     @Override
     public int updateAiUser(AiUser aiUser) {
+        AiUser old = aiUser.getId() != null ? aiUserMapper.selectById(aiUser.getId()) : null;
+        if (old != null) {
+            Long newDeptId = aiUser.getDeptId() != null ? aiUser.getDeptId() : old.getDeptId();
+            Integer newStatus = aiUser.getStatus() != null ? aiUser.getStatus() : old.getStatus();
+            if (newStatus != null && newStatus == 0) {
+                assertDeptAiUserWithinLimit(newDeptId, aiUser.getId());
+            }
+        }
         aiUser.setUpdateTime(DateUtils.getNowDate());
         if (StringUtils.isNotEmpty(aiUser.getPassword())) {
             // 登录后 update 常带上库里的 BCrypt 密文；勿对密文再 encrypt，否则第二次登录永远密码错误
@@ -176,6 +212,16 @@ public class AiUserServiceImpl implements IAiUserService {
 
     @Override
     public int updateAiUserDept(Long userId, Long deptId) {
+        if (deptId != null) {
+            AiUser u = aiUserMapper.selectById(userId);
+            if (u != null) {
+                Integer st = u.getStatus();
+                boolean normal = (st == null || st == 0);
+                if (normal) {
+                    assertDeptAiUserWithinLimit(deptId, userId);
+                }
+            }
+        }
         return aiUserMapper.updateAiUserDeptId(userId, deptId);
     }
 
@@ -204,6 +250,11 @@ public class AiUserServiceImpl implements IAiUserService {
 
     @Override
     public int updateUserStatus(AiUser aiUser) {
+        AiUser old = aiUser.getId() != null ? aiUserMapper.selectById(aiUser.getId()) : null;
+        Integer newStatus = aiUser.getStatus() != null ? aiUser.getStatus() : (old != null ? old.getStatus() : null);
+        if (old != null && newStatus != null && newStatus == 0 && old.getDeptId() != null) {
+            assertDeptAiUserWithinLimit(old.getDeptId(), aiUser.getId());
+        }
         return aiUserMapper.updateById(aiUser);
     }
 
diff --git a/web-api/ruoyi-system/src/main/resources/mapper/system/AiUserMapper.xml b/web-api/ruoyi-system/src/main/resources/mapper/system/AiUserMapper.xml
index 5af6704..fd96547 100644
--- a/web-api/ruoyi-system/src/main/resources/mapper/system/AiUserMapper.xml
+++ b/web-api/ruoyi-system/src/main/resources/mapper/system/AiUserMapper.xml
@@ -86,6 +86,14 @@ PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
     <select id="countAiUserByDeptId" resultType="int">
         select count(1) from ai_user where del_flag = '0' and dept_id = #{deptId}
     </select>
+
+    <select id="countNormalAiUsersByDeptId" resultType="int">
+        select count(1) from ai_user
+        where del_flag = '0' and status = 0 and dept_id = #{deptId}
+        <if test="excludeUserId != null">
+            and id != #{excludeUserId}
+        </if>
+    </select>
     <select id="selectPasswordById" resultType="java.lang.String">
         select password from ai_user where id = #{id}
     </select>
diff --git a/web-api/ruoyi-system/src/main/resources/mapper/system/SysUserMapper.xml b/web-api/ruoyi-system/src/main/resources/mapper/system/SysUserMapper.xml
index 29c7ad5..c390522 100644
--- a/web-api/ruoyi-system/src/main/resources/mapper/system/SysUserMapper.xml
+++ b/web-api/ruoyi-system/src/main/resources/mapper/system/SysUserMapper.xml
@@ -219,5 +219,21 @@ PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  			#{userId}
         </foreach> 
  	</delete>
+
+	<!-- 统计部门下启用中用户（未删除且 status=0），与 Java 注释一致 -->
+	<select id="countNormalUsersByDeptId" resultType="int">
+		select count(*) from sys_user u
+		where u.del_flag = '0' and u.status = '0'
+		and u.dept_id = #{deptId}
+		<if test="excludeUserId != null">
+			and u.user_id != #{excludeUserId}
+		</if>
+	</select>
+
+	<!-- 部门下后台用户数量（含停用，不含已删除） -->
+	<select id="countSysUsersByDeptId" resultType="int">
+		select count(*) from sys_user u
+		where u.del_flag = '0' and u.dept_id = #{deptId}
+	</select>
 	
 </mapper> 
\ No newline at end of file