fix: enhance content extraction from chat response to handle multiple generations with null content

Signed-off-by: liugddx <liugddx@gmail.com>

Author: liugddx

spring-ai-client-chat/src/main/java/org/springframework/ai/chat/client/DefaultChatClient.java

@@ -519,23 +519,25 @@ private ChatClientResponse doGetObservableChatClientResponse(ChatClientRequest c
 			return chatClientResponse != null ? chatClientResponse : ChatClientResponse.builder().build();
 		}
 
-	@Nullable
-	private static String getContentFromChatResponse(@Nullable ChatResponse chatResponse) {
-		if (chatResponse == null || CollectionUtils.isEmpty(chatResponse.getResults())) {
-			return null;
-		}
-		// Iterate through all generations to find the first one with non-null content
-		// This handles cases where models return multiple generations (e.g., Bedrock Converse API
-		// with openai.gpt-oss models may return reasoning output first with null content,
-		// followed by the actual response)
-		return chatResponse.getResults()
-			.stream()
-			.map(Generation::getOutput)
-			.map(AbstractMessage::getText)
-			.filter(text -> text != null)
-			.findFirst()
-			.orElse(null);
-	}
+		@Nullable
+		private static String getContentFromChatResponse(@Nullable ChatResponse chatResponse) {
+			if (chatResponse == null || CollectionUtils.isEmpty(chatResponse.getResults())) {
+				return null;
+			}
+			// Iterate through all generations to find the first one with non-null content
+			// This handles cases where models return multiple generations (e.g., Bedrock
+			// Converse API
+			// with openai.gpt-oss models may return reasoning output first with null
+			// content,
+			// followed by the actual response)
+			return chatResponse.getResults()
+				.stream()
+				.map(Generation::getOutput)
+				.map(AbstractMessage::getText)
+				.filter(text -> text != null)
+				.findFirst()
+				.orElse(null);
+		}
 
 	}
 

spring-ai-client-chat/src/test/java/org/springframework/ai/chat/client/DefaultChatClientTests.java

@@ -972,14 +972,23 @@ void whenChatResponseContentIsNull() {
 	@Test
 	void whenMultipleGenerationsWithFirstContentNull() {
 		// Test case for Bedrock Converse API with openai.gpt-oss models
-		// which return multiple generations where the first one has null content (reasoning output)
+		// which return multiple generations where the first one has null content
+		// (reasoning output)
 		// and the second one contains the actual response
 		ChatModel chatModel = mock(ChatModel.class);
 		ArgumentCaptor<Prompt> promptCaptor = ArgumentCaptor.forClass(Prompt.class);
-		given(chatModel.call(promptCaptor.capture())).willReturn(new ChatResponse(List.of(
-				new Generation(new AssistantMessage(null)), // First generation with null content
-				new Generation(new AssistantMessage("Hello! How can I help you today?")) // Second generation with actual content
-		)));
+		given(chatModel.call(promptCaptor.capture()))
+			.willReturn(new ChatResponse(List.of(new Generation(new AssistantMessage(null)), // First
+																								// generation
+																								// with
+																								// null
+																								// content
+					new Generation(new AssistantMessage("Hello! How can I help you today?")) // Second
+																								// generation
+																								// with
+																								// actual
+																								// content
+			)));
 
 		ChatClient chatClient = new DefaultChatClientBuilder(chatModel).build();
 		DefaultChatClient.DefaultChatClientRequestSpec chatClientRequestSpec = (DefaultChatClient.DefaultChatClientRequestSpec) chatClient