fix(model): Fix NPE when OpenAIClient stream call handle error

agentscope-core/src/main/java/io/agentscope/core/model/exception/OpenAIException.java

@@ -54,6 +54,13 @@ public OpenAIException(String message, int statusCode, String errorCode, String
         this.responseBody = responseBody;
     }
 
+    public OpenAIException(String message, String errorCode, String responseBody) {
+        super(message);
+        this.statusCode = null;
+        this.errorCode = errorCode;
+        this.responseBody = responseBody;
+    }
+
     /**
      * Factory method to create appropriate exception subclass based on status code.
      *
@@ -64,7 +71,10 @@ public OpenAIException(String message, int statusCode, String errorCode, String
      * @return Appropriate exception subclass
      */
     public static OpenAIException create(
-            int statusCode, String message, String errorCode, String responseBody) {
+            Integer statusCode, String message, String errorCode, String responseBody) {
+        if (null == statusCode) {
+            return new OpenAIException(message, errorCode, responseBody);
+        }
         return switch (statusCode) {
             case 400 -> new BadRequestException(message, errorCode, responseBody);
             case 401 -> new AuthenticationException(message, errorCode, responseBody);

agentscope-core/src/test/java/io/agentscope/core/model/OpenAIClientTest.java

@@ -882,4 +882,35 @@ void testCustomEndpointPathInStreamCall() throws Exception {
                 recordedRequest.getPath().contains("/v4/chat/completions"),
                 "Stream path should contain custom endpoint path: " + recordedRequest.getPath());
     }
+
+    @Test
+    @DisplayName("Should throw OpenAIException when handle custom endpoint path in stream call")
+    void testThrowOpenAIExceptionWhenCustomEndpointPathInStreamCall() {
+        String sseResponse = "";
+
+        mockServer.enqueue(
+                new MockResponse()
+                        .setBody(sseResponse)
+                        .setResponseCode(301)
+                        .setHeader("Content-Type", "text/event-stream"));
+
+        OpenAIRequest request =
+                OpenAIRequest.builder()
+                        .model("gpt-4")
+                        .messages(
+                                List.of(
+                                        OpenAIMessage.builder()
+                                                .role("user")
+                                                .content("Hello")
+                                                .build()))
+                        .build();
+
+        // Use custom endpoint path for stream call
+        GenerateOptions options =
+                GenerateOptions.builder().endpointPath("/v4/chat/completions").build();
+
+        assertThrows(
+                OpenAIException.class,
+                () -> client.stream(TEST_API_KEY, baseUrl, request, options).collectList().block());
+    }
 }