diff --git a/agentscope-core/src/main/java/io/agentscope/core/model/OpenAIChatModel.java b/agentscope-core/src/main/java/io/agentscope/core/model/OpenAIChatModel.java
index c6a8dd023..3ab107cad 100644
--- a/agentscope-core/src/main/java/io/agentscope/core/model/OpenAIChatModel.java
+++ b/agentscope-core/src/main/java/io/agentscope/core/model/OpenAIChatModel.java
@@ -199,7 +199,7 @@ public static Builder builder() {
     public static class Builder {
         private String apiKey;
         private String modelName;
-        private Boolean stream;
+        private boolean stream = true;
         private GenerateOptions defaultOptions;
         private String baseUrl;
         private String endpointPath;