diff --git a/agents-flex-core/src/main/java/com/agentsflex/core/chain/RefType.java b/agents-flex-core/src/main/java/com/agentsflex/core/chain/RefType.java
new file mode 100644
index 0000000..d0d9412
--- /dev/null
+++ b/agents-flex-core/src/main/java/com/agentsflex/core/chain/RefType.java
@@ -0,0 +1,35 @@
+package com.agentsflex.core.chain;
+
+import com.alibaba.fastjson.annotation.JSONType;
+
+@JSONType(typeName = "RefType")
+public enum RefType {
+    REF("ref"),
+    FIXED("fixed"),
+    INPUT("input"),
+    ;
+
+    private final String value;
+
+    RefType(String value) {
+        this.value = value;
+    }
+
+    public String getValue() {
+        return value;
+    }
+
+    @Override
+    public String toString() {
+        return value;
+    }
+
+    public static RefType ofValue(String value) {
+        for (RefType type : RefType.values()) {
+            if (type.value.equals(value)) {
+                return type;
+            }
+        }
+        return null;
+    }
+}