perf: use AssistantMessage#builder()

auto-configurations/models/chat/memory/repository/spring-ai-autoconfigure-model-chat-memory-repository-neo4j/src/test/java/org/springframework/ai/model/chat/memory/repository/neo4j/autoconfigure/Neo4jChatMemoryRepositoryAutoConfigurationIT.java

@@ -83,8 +83,11 @@ void addAndGet() {
 			memory.deleteByConversationId(sessionId);
 			assertThat(memory.findByConversationId(sessionId)).isEmpty();
 
-			AssistantMessage assistantMessage = new AssistantMessage("test answer", Map.of(),
-					List.of(new AssistantMessage.ToolCall("id", "type", "name", "arguments")));
+			AssistantMessage assistantMessage = AssistantMessage.builder()
+				.content("test answer")
+				.properties(Map.of())
+				.toolCalls(List.of(new AssistantMessage.ToolCall("id", "type", "name", "arguments")))
+				.build();
 
 			memory.saveAll(sessionId, List.of(userMessage, assistantMessage));
 			messages = memory.findByConversationId(sessionId);

auto-configurations/vector-stores/spring-ai-autoconfigure-vector-store-chroma/src/test/java/org/springframework/ai/vectorstore/chroma/autoconfigure/ChromaVectorStoreAutoConfigurationIT.java

@@ -95,8 +95,10 @@ public void verifyThatChromaCanHandleComplexMetadataValues() {
 
 			var response = ChatClientResponse.builder()
 				.chatResponse(ChatResponse.builder()
-					.generations(List
-						.of(new Generation(new AssistantMessage("AssistantMessage", Map.of("annotations", List.of())))))
+					.generations(List.of(new Generation(AssistantMessage.builder()
+						.content("AssistantMessage")
+						.properties(Map.of("annotations", List.of()))
+						.build())))
 					.build())
 				.build();
 			var res2 = advisor.after(response, null);

mcp/common/src/main/java/org/springframework/ai/mcp/McpToolUtils.java

@@ -433,7 +433,7 @@ public static List<ToolCallback> getToolCallbacksFromAsyncClients(List<McpAsyncC
 		if (CollectionUtils.isEmpty(asyncMcpClients)) {
 			return List.of();
 		}
-		return List.of((new AsyncMcpToolCallbackProvider(asyncMcpClients).getToolCallbacks()));
+		return List.of((AsyncMcpToolCallbackProvider.builder().mcpClients(asyncMcpClients).build().getToolCallbacks()));
 	}
 
 	@JsonIgnoreProperties(ignoreUnknown = true)

memory/repository/spring-ai-model-chat-memory-repository-cassandra/src/main/java/org/springframework/ai/chat/memory/repository/cassandra/CassandraChatMemoryRepository.java

@@ -209,7 +209,7 @@ private Message getMessage(UdtValue udt) {
 		Map<String, Object> props = Map.of(CONVERSATION_TS, udt.getInstant(this.conf.messageUdtTimestampColumn));
 		switch (MessageType.valueOf(udt.getString(this.conf.messageUdtTypeColumn))) {
 			case ASSISTANT:
-				return new AssistantMessage(content, props);
+				return AssistantMessage.builder().content(content).properties(props).build();
 			case USER:
 				return UserMessage.builder().text(content).metadata(props).build();
 			case SYSTEM:

memory/repository/spring-ai-model-chat-memory-repository-neo4j/src/main/java/org/springframework/ai/chat/memory/repository/neo4j/Neo4jChatMemoryRepository.java

@@ -183,14 +183,16 @@ private Message buildToolMessage(org.neo4j.driver.Record record) {
 
 	private Message buildAssistantMessage(org.neo4j.driver.Record record, Map<String, Object> messageMap,
 			List<Media> mediaList) {
-		Message message;
-		message = new AssistantMessage(messageMap.get(MessageAttributes.TEXT_CONTENT.getValue()).toString(),
-				record.get("metadata").asMap(Map.of()), record.get("toolCalls").asList(v -> {
-					var toolCallMap = v.asMap();
-					return new AssistantMessage.ToolCall((String) toolCallMap.get("id"),
-							(String) toolCallMap.get("type"), (String) toolCallMap.get("name"),
-							(String) toolCallMap.get("arguments"));
-				}), mediaList);
+		Message message = AssistantMessage.builder()
+			.content(messageMap.get(MessageAttributes.TEXT_CONTENT.getValue()).toString())
+			.properties(record.get("metadata").asMap(Map.of()))
+			.toolCalls(record.get("toolCalls").asList(v -> {
+				var toolCallMap = v.asMap();
+				return new AssistantMessage.ToolCall((String) toolCallMap.get("id"), (String) toolCallMap.get("type"),
+						(String) toolCallMap.get("name"), (String) toolCallMap.get("arguments"));
+			}))
+			.media(mediaList)
+			.build();
 		return message;
 	}
 

memory/repository/spring-ai-model-chat-memory-repository-neo4j/src/test/java/org/springframework/ai/chat/memory/repository/neo4j/Neo4jChatMemoryRepositoryIT.java

@@ -263,9 +263,12 @@ void handleMediaContent() {
 	void handleAssistantMessageWithToolCalls() {
 		var conversationId = UUID.randomUUID().toString();
 
-		AssistantMessage assistantMessage = new AssistantMessage("Message with tool calls", Map.of(),
-				List.of(new AssistantMessage.ToolCall("id1", "type1", "name1", "arguments1"),
-						new AssistantMessage.ToolCall("id2", "type2", "name2", "arguments2")));
+		AssistantMessage assistantMessage = AssistantMessage.builder()
+			.content("Message with tool calls")
+			.properties(Map.of())
+			.toolCalls(List.of(new AssistantMessage.ToolCall("id1", "type1", "name1", "arguments1"),
+					new AssistantMessage.ToolCall("id2", "type2", "name2", "arguments2")))
+			.build();
 
 		this.chatMemoryRepository.saveAll(conversationId, List.<Message>of(assistantMessage));
 
@@ -389,7 +392,8 @@ void saveAndFindMessagesWithEmptyContentOrMetadata() {
 		assertThat(retrievedEmptyContentMsg.getMetadata().keySet()).hasSize(1); // Only
 																				// messageType
 
-		// Verify second message (empty metadata from input, should only have messageType
+		// Verify second message (empty metadata from input, should only have
+		// messageType
 		// after retrieval)
 		Message retrievedEmptyMetadataMsg = retrievedMessages.get(1);
 		assertThat(retrievedEmptyMetadataMsg).isInstanceOf(UserMessage.class);

models/spring-ai-anthropic/src/main/java/org/springframework/ai/anthropic/AnthropicChatModel.java

@@ -321,19 +321,24 @@ private ChatResponse toChatResponse(ChatCompletionResponse chatCompletion, Usage
 		for (ContentBlock content : chatCompletion.content()) {
 			switch (content.type()) {
 				case TEXT, TEXT_DELTA:
-					generations.add(new Generation(new AssistantMessage(content.text(), Map.of()),
+					generations.add(new Generation(
+							AssistantMessage.builder().content(content.text()).properties(Map.of()).build(),
 							ChatGenerationMetadata.builder().finishReason(chatCompletion.stopReason()).build()));
 					break;
 				case THINKING, THINKING_DELTA:
 					Map<String, Object> thinkingProperties = new HashMap<>();
 					thinkingProperties.put("signature", content.signature());
-					generations.add(new Generation(new AssistantMessage(content.thinking(), thinkingProperties),
+					generations.add(new Generation(
+							AssistantMessage.builder()
+								.content(content.thinking())
+								.properties(thinkingProperties)
+								.build(),
 							ChatGenerationMetadata.builder().finishReason(chatCompletion.stopReason()).build()));
 					break;
 				case REDACTED_THINKING:
 					Map<String, Object> redactedProperties = new HashMap<>();
 					redactedProperties.put("data", content.data());
-					generations.add(new Generation(new AssistantMessage(null, redactedProperties),
+					generations.add(new Generation(AssistantMessage.builder().properties(redactedProperties).build(),
 							ChatGenerationMetadata.builder().finishReason(chatCompletion.stopReason()).build()));
 					break;
 				case TOOL_USE:
@@ -347,13 +352,17 @@ private ChatResponse toChatResponse(ChatCompletionResponse chatCompletion, Usage
 		}
 
 		if (chatCompletion.stopReason() != null && generations.isEmpty()) {
-			Generation generation = new Generation(new AssistantMessage(null, Map.of()),
+			Generation generation = new Generation(AssistantMessage.builder().content("").properties(Map.of()).build(),
 					ChatGenerationMetadata.builder().finishReason(chatCompletion.stopReason()).build());
 			generations.add(generation);
 		}
 
 		if (!CollectionUtils.isEmpty(toolCalls)) {
-			AssistantMessage assistantMessage = new AssistantMessage("", Map.of(), toolCalls);
+			AssistantMessage assistantMessage = AssistantMessage.builder()
+				.content("")
+				.properties(Map.of())
+				.toolCalls(toolCalls)
+				.build();
 			Generation toolCallGeneration = new Generation(assistantMessage,
 					ChatGenerationMetadata.builder().finishReason(chatCompletion.stopReason()).build());
 			generations.add(toolCallGeneration);

models/spring-ai-azure-openai/src/main/java/org/springframework/ai/azure/openai/AzureOpenAiChatModel.java

@@ -493,7 +493,11 @@ private Generation buildGeneration(ChatChoice choice, Map<String, Object> metada
 		}
 
 		var content = responseMessage == null ? "" : responseMessage.getContent();
-		var assistantMessage = new AssistantMessage(content, metadata, toolCalls);
+		var assistantMessage = AssistantMessage.builder()
+			.content(content)
+			.properties(metadata)
+			.toolCalls(toolCalls)
+			.build();
 		var generationMetadata = generateChoiceMetadata(choice);
 
 		return new Generation(assistantMessage, generationMetadata);

models/spring-ai-bedrock-converse/src/main/java/org/springframework/ai/bedrock/converse/BedrockProxyChatModel.java

@@ -572,14 +572,15 @@ private ChatResponse toChatResponse(ConverseResponse response, ChatResponse perv
 		List<Generation> generations = message.content()
 			.stream()
 			.filter(content -> content.type() != ContentBlock.Type.TOOL_USE)
-			.map(content -> new Generation(new AssistantMessage(content.text(), Map.of()),
+			.map(content -> new Generation(
+					AssistantMessage.builder().content(content.text()).properties(Map.of()).build(),
 					ChatGenerationMetadata.builder().finishReason(response.stopReasonAsString()).build()))
 			.toList();
 
 		List<Generation> allGenerations = new ArrayList<>(generations);
 
 		if (response.stopReasonAsString() != null && generations.isEmpty()) {
-			Generation generation = new Generation(new AssistantMessage(null, Map.of()),
+			Generation generation = new Generation(AssistantMessage.builder().properties(Map.of()).build(),
 					ChatGenerationMetadata.builder().finishReason(response.stopReasonAsString()).build());
 			allGenerations.add(generation);
 		}
@@ -603,7 +604,11 @@ private ChatResponse toChatResponse(ConverseResponse response, ChatResponse perv
 					.add(new AssistantMessage.ToolCall(functionCallId, "function", functionName, functionArguments));
 			}
 
-			AssistantMessage assistantMessage = new AssistantMessage("", Map.of(), toolCalls);
+			AssistantMessage assistantMessage = AssistantMessage.builder()
+				.content("")
+				.properties(Map.of())
+				.toolCalls(toolCalls)
+				.build();
 			Generation toolCallGeneration = new Generation(assistantMessage,
 					ChatGenerationMetadata.builder().finishReason(response.stopReasonAsString()).build());
 			allGenerations.add(toolCallGeneration);

models/spring-ai-bedrock-converse/src/main/java/org/springframework/ai/bedrock/converse/api/ConverseApiUtils.java

@@ -140,7 +140,11 @@ public static Flux<ChatResponse> toChatResponse(Flux<ConverseStreamOutput> respo
 					}
 				}
 
-				AssistantMessage assistantMessage = new AssistantMessage("", Map.of(), toolCalls);
+				AssistantMessage assistantMessage = AssistantMessage.builder()
+					.content("")
+					.properties(Map.of())
+					.toolCalls(toolCalls)
+					.build();
 				Generation toolCallGeneration = new Generation(assistantMessage,
 						ChatGenerationMetadata.builder().finishReason("tool_use").build());
 
@@ -176,7 +180,10 @@ else if (nextEvent instanceof ContentBlockDeltaEvent contentBlockDeltaEvent) {
 				if (contentBlockDeltaEvent.delta().type().equals(ContentBlockDelta.Type.TEXT)) {
 
 					var generation = new Generation(
-							new AssistantMessage(contentBlockDeltaEvent.delta().text(), Map.of()),
+							AssistantMessage.builder()
+								.content(contentBlockDeltaEvent.delta().text())
+								.properties(Map.of())
+								.build(),
 							ChatGenerationMetadata.builder()
 								.finishReason(lastAggregation.metadataAggregation().stopReason())
 								.build());

models/spring-ai-google-genai/src/main/java/org/springframework/ai/google/genai/GoogleGenAiChatModel.java

@@ -616,7 +616,11 @@ protected List<Generation> responseCandidateToGeneration(Candidate candidate) {
 				})
 				.toList();
 
-			AssistantMessage assistantMessage = new AssistantMessage("", messageMetadata, assistantToolCalls);
+			AssistantMessage assistantMessage = AssistantMessage.builder()
+				.content("")
+				.properties(messageMetadata)
+				.toolCalls(assistantToolCalls)
+				.build();
 
 			return List.of(new Generation(assistantMessage, chatGenerationMetadata));
 		}
@@ -626,7 +630,10 @@ protected List<Generation> responseCandidateToGeneration(Candidate candidate) {
 				.parts()
 				.orElse(List.of())
 				.stream()
-				.map(part -> new AssistantMessage(part.text().orElse(""), messageMetadata))
+				.map(part -> AssistantMessage.builder()
+					.content(part.text().orElse(""))
+					.properties(messageMetadata)
+					.build())
 				.map(assistantMessage -> new Generation(assistantMessage, chatGenerationMetadata))
 				.toList();
 		}

models/spring-ai-huggingface/src/main/java/org/springframework/ai/huggingface/HuggingfaceChatModel.java

@@ -104,7 +104,8 @@ public ChatResponse call(Prompt prompt) {
 					new TypeReference<>() {
 
 					});
-			Generation generation = new Generation(new AssistantMessage(generatedText, detailsMap));
+			Generation generation = new Generation(
+					AssistantMessage.builder().content(generatedText).properties(detailsMap).build());
 			generations.add(generation);
 		}
 		return new ChatResponse(generations);

models/spring-ai-minimax/src/main/java/org/springframework/ai/minimax/MiniMaxChatModel.java

@@ -226,7 +226,11 @@ private static Generation buildGeneration(Choice choice, Map<String, Object> met
 						acc1.addAll(acc2);
 						return acc1;
 					});
-		var assistantMessage = new AssistantMessage(choice.message().content(), metadata, toolCalls);
+		var assistantMessage = AssistantMessage.builder()
+			.content(choice.message().content())
+			.properties(metadata)
+			.toolCalls(toolCalls)
+			.build();
 		String finishReason = (choice.finishReason() != null ? choice.finishReason().name() : "");
 		var generationMetadata = ChatGenerationMetadata.builder().finishReason(finishReason).build();
 		return new Generation(assistantMessage, generationMetadata);
@@ -432,7 +436,11 @@ private Generation buildGeneration(ChatCompletionMessage message, ChatCompletion
 							toolCall.function().name(), toolCall.function().arguments()))
 					.toList();
 
-		var assistantMessage = new AssistantMessage(message.content(), metadata, toolCalls);
+		var assistantMessage = AssistantMessage.builder()
+			.content(message.content())
+			.properties(metadata)
+			.toolCalls(toolCalls)
+			.build();
 		String finishReason = (completionFinishReason != null ? completionFinishReason.name() : "");
 		var generationMetadata = ChatGenerationMetadata.builder().finishReason(finishReason).build();
 		return new Generation(assistantMessage, generationMetadata);

models/spring-ai-mistral-ai/src/main/java/org/springframework/ai/mistralai/MistralAiChatModel.java

@@ -362,7 +362,11 @@ private Generation buildGeneration(Choice choice, Map<String, Object> metadata)
 							toolCall.function().name(), toolCall.function().arguments()))
 					.toList();
 
-		var assistantMessage = new AssistantMessage(choice.message().content(), metadata, toolCalls);
+		var assistantMessage = AssistantMessage.builder()
+			.content(choice.message().content())
+			.properties(metadata)
+			.toolCalls(toolCalls)
+			.build();
 		String finishReason = (choice.finishReason() != null ? choice.finishReason().name() : "");
 		var generationMetadata = ChatGenerationMetadata.builder().finishReason(finishReason).build();
 		return new Generation(assistantMessage, generationMetadata);

models/spring-ai-oci-genai/src/main/java/org/springframework/ai/oci/cohere/OCICohereChatModel.java

@@ -200,7 +200,7 @@ private List<Generation> toGenerations(com.oracle.bmc.generativeaiinference.resp
 			ChatGenerationMetadata metadata = ChatGenerationMetadata.builder()
 				.finishReason(resp.getFinishReason().getValue())
 				.build();
-			AssistantMessage message = new AssistantMessage(resp.getText(), Map.of());
+			AssistantMessage message = AssistantMessage.builder().content(resp.getText()).properties(Map.of()).build();
 			generations.add(new Generation(message, metadata));
 			return generations;
 		}

models/spring-ai-ollama/src/main/java/org/springframework/ai/ollama/OllamaChatModel.java

@@ -255,7 +255,11 @@ private ChatResponse internalCall(Prompt prompt, ChatResponse previousChatRespon
 									ModelOptionsUtils.toJsonString(toolCall.function().arguments())))
 							.toList();
 
-				var assistantMessage = new AssistantMessage(ollamaResponse.message().content(), Map.of(), toolCalls);
+				var assistantMessage = AssistantMessage.builder()
+					.content(ollamaResponse.message().content())
+					.properties(Map.of())
+					.toolCalls(toolCalls)
+					.build();
 
 				ChatGenerationMetadata generationMetadata = ChatGenerationMetadata.NULL;
 				if (ollamaResponse.promptEvalCount() != null && ollamaResponse.evalCount() != null) {
@@ -333,7 +337,11 @@ private Flux<ChatResponse> internalStream(Prompt prompt, ChatResponse previousCh
 						.toList();
 				}
 
-				var assistantMessage = new AssistantMessage(content, Map.of(), toolCalls);
+				var assistantMessage = AssistantMessage.builder()
+					.content(content)
+					.properties(Map.of())
+					.toolCalls(toolCalls)
+					.build();
 
 				ChatGenerationMetadata generationMetadata = ChatGenerationMetadata.NULL;
 				if (chunk.promptEvalCount() != null && chunk.evalCount() != null) {

models/spring-ai-openai/src/main/java/org/springframework/ai/openai/OpenAiChatModel.java

@@ -448,7 +448,12 @@ private Generation buildGeneration(Choice choice, Map<String, Object> metadata,
 			generationMetadataBuilder.metadata("logprobs", choice.logprobs());
 		}
 
-		var assistantMessage = new AssistantMessage(textContent, metadata, toolCalls, media);
+		var assistantMessage = AssistantMessage.builder()
+			.content(textContent)
+			.properties(metadata)
+			.toolCalls(toolCalls)
+			.media(media)
+			.build();
 		return new Generation(assistantMessage, generationMetadataBuilder.build());
 	}
 

models/spring-ai-vertex-ai-gemini/src/main/java/org/springframework/ai/vertexai/gemini/VertexAiGeminiChatModel.java

@@ -631,15 +631,19 @@ protected List<Generation> responseCandidateToGeneration(Candidate candidate) {
 				})
 				.toList();
 
-			AssistantMessage assistantMessage = new AssistantMessage("", messageMetadata, assistantToolCalls);
+			AssistantMessage assistantMessage = AssistantMessage.builder()
+				.content("")
+				.properties(messageMetadata)
+				.toolCalls(assistantToolCalls)
+				.build();
 
 			return List.of(new Generation(assistantMessage, chatGenerationMetadata));
 		}
 		else {
 			List<Generation> generations = candidate.getContent()
 				.getPartsList()
 				.stream()
-				.map(part -> new AssistantMessage(part.getText(), messageMetadata))
+				.map(part -> AssistantMessage.builder().content(part.getText()).properties(messageMetadata).build())
 				.map(assistantMessage -> new Generation(assistantMessage, chatGenerationMetadata))
 				.toList();
 

spring-ai-model/src/main/java/org/springframework/ai/chat/model/MessageAggregator.java

@@ -28,6 +28,7 @@
 import reactor.core.publisher.Flux;
 
 import org.springframework.ai.chat.messages.AssistantMessage;
+import org.springframework.ai.chat.messages.AssistantMessage.ToolCall;
 import org.springframework.ai.chat.metadata.ChatGenerationMetadata;
 import org.springframework.ai.chat.metadata.ChatResponseMetadata;
 import org.springframework.ai.chat.metadata.EmptyRateLimit;
@@ -157,12 +158,17 @@ public Flux<ChatResponse> aggregate(Flux<ChatResponse> fluxChatResponse,
 
 			if (!CollectionUtils.isEmpty(collectedToolCalls)) {
 
-				finalAssistantMessage = new AssistantMessage(messageTextContentRef.get().toString(),
-						messageMetadataMapRef.get(), collectedToolCalls);
+				finalAssistantMessage = AssistantMessage.builder()
+					.content(messageTextContentRef.get().toString())
+					.properties(messageMetadataMapRef.get())
+					.toolCalls(collectedToolCalls)
+					.build();
 			}
 			else {
-				finalAssistantMessage = new AssistantMessage(messageTextContentRef.get().toString(),
-						messageMetadataMapRef.get());
+				finalAssistantMessage = AssistantMessage.builder()
+					.content(messageTextContentRef.get().toString())
+					.properties(messageMetadataMapRef.get())
+					.build();
 			}
 			onAggregationComplete.accept(new ChatResponse(List.of(new Generation(finalAssistantMessage,