Fix Anthropic chat model functioncalling token usage

 - Accumulate the token usage when functioncalling is used
   - Fix both call() as well as stream() operations

 - Add/update tests

Author: ilayaperumalg

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

@@ -47,6 +47,9 @@
 import org.springframework.ai.chat.messages.UserMessage;
 import org.springframework.ai.chat.metadata.ChatGenerationMetadata;
 import org.springframework.ai.chat.metadata.ChatResponseMetadata;
+import org.springframework.ai.chat.metadata.EmptyUsage;
+import org.springframework.ai.chat.metadata.Usage;
+import org.springframework.ai.chat.metadata.UsageUtils;
 import org.springframework.ai.chat.model.AbstractToolCallSupport;
 import org.springframework.ai.chat.model.ChatModel;
 import org.springframework.ai.chat.model.ChatResponse;
@@ -211,6 +214,10 @@ public AnthropicChatModel(AnthropicApi anthropicApi, AnthropicChatOptions defaul
 
 	@Override
 	public ChatResponse call(Prompt prompt) {
+		return this.internalCall(prompt, null);
+	}
+
+	public ChatResponse internalCall(Prompt prompt, ChatResponse previousChatResponse) {
 		ChatCompletionRequest request = createRequest(prompt, false);
 
 		ChatModelObservationContext observationContext = ChatModelObservationContext.builder()
@@ -227,8 +234,14 @@ public ChatResponse call(Prompt prompt) {
 				ResponseEntity<ChatCompletionResponse> completionEntity = this.retryTemplate
 					.execute(ctx -> this.anthropicApi.chatCompletionEntity(request));
 
-				ChatResponse chatResponse = toChatResponse(completionEntity.getBody());
+				AnthropicApi.ChatCompletionResponse completionResponse = completionEntity.getBody();
+				AnthropicApi.Usage usage = completionResponse.usage();
 
+				Usage currentChatResponseUsage = usage != null ? AnthropicUsage.from(completionResponse.usage())
+						: new EmptyUsage();
+				Usage accumulatedUsage = UsageUtils.getCumulativeUsage(currentChatResponseUsage, previousChatResponse);
+
+				ChatResponse chatResponse = toChatResponse(completionEntity.getBody(), accumulatedUsage);
 				observationContext.setResponse(chatResponse);
 
 				return chatResponse;
@@ -237,14 +250,18 @@ public ChatResponse call(Prompt prompt) {
 		if (!isProxyToolCalls(prompt, this.defaultOptions) && response != null
 				&& this.isToolCall(response, Set.of("tool_use"))) {
 			var toolCallConversation = handleToolCalls(prompt, response);
-			return this.call(new Prompt(toolCallConversation, prompt.getOptions()));
+			return this.internalCall(new Prompt(toolCallConversation, prompt.getOptions()), response);
 		}
 
 		return response;
 	}
 
 	@Override
 	public Flux<ChatResponse> stream(Prompt prompt) {
+		return this.internalStream(prompt, null);
+	}
+
+	public Flux<ChatResponse> internalStream(Prompt prompt, ChatResponse previousChatResponse) {
 		return Flux.deferContextual(contextView -> {
 			ChatCompletionRequest request = createRequest(prompt, true);
 
@@ -264,11 +281,14 @@ public Flux<ChatResponse> stream(Prompt prompt) {
 
 			// @formatter:off
 			Flux<ChatResponse> chatResponseFlux = response.switchMap(chatCompletionResponse -> {
-				ChatResponse chatResponse = toChatResponse(chatCompletionResponse);
+				AnthropicApi.Usage usage = chatCompletionResponse.usage();
+				Usage currentChatResponseUsage = usage != null ? AnthropicUsage.from(chatCompletionResponse.usage()) : new EmptyUsage();
+				Usage accumulatedUsage = UsageUtils.getCumulativeUsage(currentChatResponseUsage, previousChatResponse);
+				ChatResponse chatResponse = toChatResponse(chatCompletionResponse, accumulatedUsage);
 
 				if (!isProxyToolCalls(prompt, this.defaultOptions) && this.isToolCall(chatResponse, Set.of("tool_use"))) {
 					var toolCallConversation = handleToolCalls(prompt, chatResponse);
-					return this.stream(new Prompt(toolCallConversation, prompt.getOptions()));
+					return this.internalStream(new Prompt(toolCallConversation, prompt.getOptions()), chatResponse);
 				}
 
 				return Mono.just(chatResponse);
@@ -282,7 +302,7 @@ public Flux<ChatResponse> stream(Prompt prompt) {
 		});
 	}
 
-	private ChatResponse toChatResponse(ChatCompletionResponse chatCompletion) {
+	private ChatResponse toChatResponse(ChatCompletionResponse chatCompletion, Usage usage) {
 
 		if (chatCompletion == null) {
 			logger.warn("Null chat completion returned");
@@ -328,12 +348,15 @@ private ChatResponse toChatResponse(ChatCompletionResponse chatCompletion) {
 			allGenerations.add(toolCallGeneration);
 		}
 
-		return new ChatResponse(allGenerations, this.from(chatCompletion));
+		return new ChatResponse(allGenerations, this.from(chatCompletion, usage));
 	}
 
 	private ChatResponseMetadata from(AnthropicApi.ChatCompletionResponse result) {
+		return from(result, AnthropicUsage.from(result.usage()));
+	}
+
+	private ChatResponseMetadata from(AnthropicApi.ChatCompletionResponse result, Usage usage) {
 		Assert.notNull(result, "Anthropic ChatCompletionResult must not be null");
-		AnthropicUsage usage = AnthropicUsage.from(result.usage());
 		return ChatResponseMetadata.builder()
 			.withId(result.id())
 			.withModel(result.model())

models/spring-ai-anthropic/src/test/java/org/springframework/ai/anthropic/AnthropicChatModelIT.java

@@ -37,6 +37,7 @@
 import org.springframework.ai.chat.messages.AssistantMessage;
 import org.springframework.ai.chat.messages.Message;
 import org.springframework.ai.chat.messages.UserMessage;
+import org.springframework.ai.chat.metadata.Usage;
 import org.springframework.ai.chat.model.ChatModel;
 import org.springframework.ai.chat.model.ChatResponse;
 import org.springframework.ai.chat.model.Generation;
@@ -288,7 +289,12 @@ void functionCallTest() {
 		logger.info("Response: {}", response);
 
 		Generation generation = response.getResult();
+		assertThat(generation).isNotNull();
+		assertThat(generation.getOutput()).isNotNull();
 		assertThat(generation.getOutput().getText()).contains("30", "10", "15");
+		assertThat(response.getMetadata()).isNotNull();
+		assertThat(response.getMetadata().getUsage()).isNotNull();
+		assertThat(response.getMetadata().getUsage().getTotalTokens()).isLessThan(4000).isGreaterThan(1800);
 	}
 
 	@Test
@@ -324,6 +330,35 @@ void streamFunctionCallTest() {
 		assertThat(content).contains("30", "10", "15");
 	}
 
+	@Test
+	void streamFunctionCallUsageTest() {
+
+		UserMessage userMessage = new UserMessage(
+				"What's the weather like in San Francisco, Tokyo and Paris? Return the result in Celsius.");
+
+		List<Message> messages = new ArrayList<>(List.of(userMessage));
+
+		var promptOptions = AnthropicChatOptions.builder()
+			.withModel(AnthropicApi.ChatModel.CLAUDE_3_5_SONNET.getName())
+			.withFunctionCallbacks(List.of(FunctionCallback.builder()
+				.function("getCurrentWeather", new MockWeatherService())
+				.description(
+						"Get the weather in location. Return temperature in 36°F or 36°C format. Use multi-turn if needed.")
+				.inputType(MockWeatherService.Request.class)
+				.build()))
+			.build();
+
+		Flux<ChatResponse> responseFlux = this.chatModel.stream(new Prompt(messages, promptOptions));
+
+		ChatResponse chatResponse = responseFlux.last().block();
+
+		logger.info("Response: {}", chatResponse);
+		Usage usage = chatResponse.getMetadata().getUsage();
+
+		assertThat(usage).isNotNull();
+		assertThat(usage.getTotalTokens()).isLessThan(4000).isGreaterThan(1800);
+	}
+
 	@Test
 	void validateCallResponseMetadata() {
 		String model = AnthropicApi.ChatModel.CLAUDE_2_1.getName();