diff --git a/common/common-core/src/main/java/apelet/common/core/advice/MyExceptionHandler.java b/common/common-core/src/main/java/apelet/common/core/advice/MyExceptionHandler.java
index 09b668c..89f535c 100644
--- a/common/common-core/src/main/java/apelet/common/core/advice/MyExceptionHandler.java
+++ b/common/common-core/src/main/java/apelet/common/core/advice/MyExceptionHandler.java
@@ -27,6 +27,20 @@ import java.util.concurrent.TimeoutException;
 @RestControllerAdvice("apelet")
 public class MyExceptionHandler {
 
+    /**
+     * 数据不存在或不属于当前租户：统一返回 404，避免越权探测（PRD FR-4.16）。
+     *
+     * @param ex      异常对象。
+     * @param request http请求。
+     * @return 应答对象。
+     */
+    @ExceptionHandler(value = DataNotFoundException.class)
+    public ResponseResult<Void> dataNotFoundExceptionHandle(DataNotFoundException ex, HttpServletRequest request) {
+        log.warn("Data not found or not owned by current tenant from URL [{}]", request.getRequestURI());
+        ContextUtil.getHttpResponse().setStatus(HttpServletResponse.SC_NOT_FOUND);
+        return ResponseResult.error(ErrorCodeEnum.DATA_NOT_EXIST);
+    }
+
 	/**
 	 * 通用异常处理方法。
 	 *
diff --git a/common/common-core/src/main/java/apelet/common/core/cache/CacheKey.java b/common/common-core/src/main/java/apelet/common/core/cache/CacheKey.java
index 32dd3e2..086d1bb 100644
--- a/common/common-core/src/main/java/apelet/common/core/cache/CacheKey.java
+++ b/common/common-core/src/main/java/apelet/common/core/cache/CacheKey.java
@@ -1,5 +1,7 @@
 package apelet.common.core.cache;
 
+import apelet.common.core.object.TokenData;
+
 /**
  * 在线表单缓存
  * @author Soon
@@ -19,6 +21,15 @@ public class CacheKey {
      */
     public final static String FORM_FIELD_BY_HEAD_Id = "FORM_FIELD_BY_HEAD_Id:";
 
+    /**
+     * 租户维度片段：A 端为租户Id，B 端及无请求上下文（MQ、定时任务）统一为 base。
+     * 租户库的表单元数据 id 可能相同（由管理端复制而来），不加租户维度会导致缓存互相覆盖（PRD FR-4.18）。
+     */
+    private static String tenantSegment() {
+        Long tenantId = TokenData.currentTenantId();
+        return tenantId == null ? "base" : String.valueOf(tenantId);
+    }
+
     public static String makeEntityTableKey(String datasourceVariableName) {
         return "EntityTable:" + datasourceVariableName;
     }
@@ -26,32 +37,32 @@ public class CacheKey {
 
 
     public static String makeTableKey(Long id) {
-        return "FORM_HEAD_TABLE:" + id;
+        return "FORM_HEAD_TABLE:" + tenantSegment() + ":" + id;
     }
 
     public static String makeFormHeadByTableId(Long id) {
-        return "FORM_HEAD_BY_TABLE_ID:" + id;
+        return "FORM_HEAD_BY_TABLE_ID:" + tenantSegment() + ":" + id;
     }
 
 
     public static String makeTableKey(String tableName) {
-        return "FORM_HEAD_TABLE_NAME:" + tableName;
+        return "FORM_HEAD_TABLE_NAME:" + tenantSegment() + ":" + tableName;
     }
 
 
     public static String makeChildFieldListKey(Long id) {
-        return "FORM_CHILD_FIELD:" + id;
+        return "FORM_CHILD_FIELD:" + tenantSegment() + ":" + id;
     }
 
 
     public static String makeOneToManyTable(String tableName) {
-        return "FORM_ONETOMANY_TABLE:" + tableName;
+        return "FORM_ONETOMANY_TABLE:" + tenantSegment() + ":" + tableName;
     }
 
 
 
     public static String getFormFieldByHeadId(long headId) {
-        return FORM_FIELD_BY_HEAD_Id + headId;
+        return FORM_FIELD_BY_HEAD_Id + tenantSegment() + ":" + headId;
     }
 
 
diff --git a/common/common-core/src/main/java/apelet/common/core/exception/DataNotFoundException.java b/common/common-core/src/main/java/apelet/common/core/exception/DataNotFoundException.java
new file mode 100644
index 0000000..d5acf3a
--- /dev/null
+++ b/common/common-core/src/main/java/apelet/common/core/exception/DataNotFoundException.java
@@ -0,0 +1,20 @@
+package apelet.common.core.exception;
+
+/**
+ * 数据不存在或不属于当前租户。
+ *
+ * <p>用于按 id 查询/更新/删除时的归属校验（PRD FR-4.16）：
+ * 记录不存在与记录属于其他租户统一返回 404，避免通过状态码探测数据是否存在。</p>
+ *
+ * @author apelet
+ */
+public class DataNotFoundException extends MyRuntimeException {
+
+    public DataNotFoundException() {
+        super();
+    }
+
+    public DataNotFoundException(String msg) {
+        super(msg);
+    }
+}
diff --git a/common/common-core/src/main/java/apelet/common/core/object/TokenData.java b/common/common-core/src/main/java/apelet/common/core/object/TokenData.java
index d1c49ad..edf688d 100644
--- a/common/common-core/src/main/java/apelet/common/core/object/TokenData.java
+++ b/common/common-core/src/main/java/apelet/common/core/object/TokenData.java
@@ -144,6 +144,27 @@ public class TokenData {
     }
 
     /**
+     * 当前请求的租户Id。B 端（管理端）为 null，A 端（租户端）为登录用户的租户Id。
+     * 无 HTTP 请求上下文（如 MQ 消费、定时任务）时同样返回 null。
+     *
+     * @return 当前租户Id，可能为 null。
+     */
+    public static Long currentTenantId() {
+        TokenData tokenData = takeFromRequest();
+        return tokenData == null ? null : tokenData.getTenantId();
+    }
+
+    /**
+     * 当前请求的应用编码。为空表示不按应用维度过滤（PRD FR-4.14）。
+     *
+     * @return 当前应用编码，可能为 null。
+     */
+    public static String currentAppCode() {
+        TokenData tokenData = takeFromRequest();
+        return tokenData == null ? null : tokenData.getAppCode();
+    }
+
+    /**
      * 从Http Request对象中获取令牌对象。
      *
      * @return 令牌对象。