fix(gemini): group parallel tool responses

agentscope-extensions/agentscope-extensions-model/agentscope-extensions-model-gemini/src/main/java/io/agentscope/extensions/model/gemini/formatter/GeminiMessageConverter.java

@@ -53,13 +53,13 @@
  * <ul>
  *   <li>Text blocks</li>
  *   <li>Tool use blocks (function_call)</li>
- *   <li>Tool result blocks (function_response as independent Content)</li>
+ *   <li>Tool result blocks (function_response grouped into one user Content per message)</li>
  *   <li>Multimodal content (image, audio, video)</li>
  * </ul>
  *
  * <p><b>Important Conversion Behaviors:</b>
  * <ul>
- *   <li>Tool result blocks are converted to independent "user" role Content</li>
+ *   <li>Tool result blocks from one message are converted to one "user" role Content</li>
  *   <li>Multiple tool outputs are formatted with "- " prefix per line</li>
  *   <li>System messages are treated as "user" role (Gemini API requirement)</li>
  * </ul>
@@ -88,6 +88,7 @@ public List<Content> convertMessages(List<Msg> msgs) {
 
         for (Msg msg : msgs) {
             List<Part> parts = new ArrayList<>();
+            List<Part> toolResultParts = new ArrayList<>();
 
             for (ContentBlock block : msg.getContent()) {
                 if (block instanceof TextBlock tb) {
@@ -137,7 +138,7 @@ public List<Content> convertMessages(List<Msg> msgs) {
                     parts.add(partBuilder.build());
 
                 } else if (block instanceof ToolResultBlock trb) {
-                    // IMPORTANT: Tool result as independent Content with "user" role
+                    // Tool results from the same message share one user Content.
                     String textOutput = convertToolResultToString(trb.getOutput());
 
                     // Create response map with "output" key
@@ -154,14 +155,7 @@ public List<Content> convertMessages(List<Msg> msgs) {
                     Part functionResponsePart =
                             Part.builder().functionResponse(functionResponse).build();
 
-                    Content toolResultContent =
-                            Content.builder()
-                                    .role("user")
-                                    .parts(List.of(functionResponsePart))
-                                    .build();
-
-                    result.add(toolResultContent);
-                    // Skip adding to current message parts
+                    toolResultParts.add(functionResponsePart);
                     continue;
 
                 } else if (block instanceof ImageBlock ib) {
@@ -190,6 +184,12 @@ public List<Content> convertMessages(List<Msg> msgs) {
                 }
             }
 
+            if (!toolResultParts.isEmpty()) {
+                Content toolResultContent =
+                        Content.builder().role("user").parts(toolResultParts).build();
+                result.add(toolResultContent);
+            }
+
             // Add message if there are parts
             if (!parts.isEmpty()) {
                 String role = convertRole(msg.getRole());

agentscope-extensions/agentscope-extensions-model/agentscope-extensions-model-gemini/src/test/java/io/agentscope/extensions/model/gemini/formatter/GeminiMessageConverterTest.java

@@ -223,6 +223,38 @@ void testConvertToolResultBlock() {
         assertEquals("Result text", part.functionResponse().get().response().get().get("output"));
     }
 
+    @Test
+    @DisplayName("Should group tool results from one message into one user Content")
+    void testConvertMultipleToolResultBlocks() {
+        ToolResultBlock firstResult =
+                ToolResultBlock.builder()
+                        .id("call_123")
+                        .name("search")
+                        .output(List.of(TextBlock.builder().text("First result").build()))
+                        .build();
+        ToolResultBlock secondResult =
+                ToolResultBlock.builder()
+                        .id("call_456")
+                        .name("lookup")
+                        .output(List.of(TextBlock.builder().text("Second result").build()))
+                        .build();
+        Msg msg =
+                Msg.builder()
+                        .name("system")
+                        .content(List.of(firstResult, secondResult))
+                        .role(MsgRole.TOOL)
+                        .build();
+
+        List<Content> result = converter.convertMessages(List.of(msg));
+
+        assertEquals(1, result.size());
+        Content content = result.get(0);
+        assertEquals("user", content.role().get());
+        assertEquals(2, content.parts().get().size());
+        assertEquals("call_123", content.parts().get().get(0).functionResponse().get().id().get());
+        assertEquals("call_456", content.parts().get().get(1).functionResponse().get().id().get());
+    }
+
     @Test
     @DisplayName("Should format tool result with single output")
     void testToolResultSingleOutput() {