fix(deepseek): reset tool_choice handling to prevent infinite loop when returnDirect=false (#4617)

Signed-off-by: Kuntal Maity <[email protected]>

Author: kuntal1461

models/spring-ai-deepseek/src/main/java/org/springframework/ai/deepseek/DeepSeekChatModel.java

@@ -76,6 +76,7 @@
  * backed by {@link DeepSeekApi}.
  *
  * @author Geng Rong
+ * @last Updated By : @kuntal1461
  */
 public class DeepSeekChatModel implements ChatModel {
 
@@ -193,7 +194,10 @@ public ChatResponse internalCall(Prompt prompt, ChatResponse previousChatRespons
 				}).toList();
 
 				// Current usage
-				DeepSeekApi.Usage usage = completionEntity.getBody().usage();
+				DeepSeekApi.Usage usage = null;
+				if (completionEntity != null && completionEntity.getBody() != null) {
+					usage = chatCompletion.usage();
+				}
 				Usage currentChatResponseUsage = usage != null ? getDefaultUsage(usage) : new EmptyUsage();
 				Usage accumulatedUsage = UsageCalculator.getCumulativeUsage(currentChatResponseUsage,
 						previousChatResponse);
@@ -216,6 +220,10 @@ public ChatResponse internalCall(Prompt prompt, ChatResponse previousChatRespons
 					.build();
 			}
 			else {
+				// Reset tool choice to AUTO to prevent forcing repeated tool calls.
+				if (prompt.getOptions() instanceof DeepSeekChatOptions options) {
+					options.setToolChoice(ChatCompletionRequest.ToolChoiceBuilder.AUTO);
+				}
 				// Send the tool execution result back to the model.
 				return this.internalCall(new Prompt(toolExecutionResult.conversationHistory(), prompt.getOptions()),
 						response);
@@ -305,6 +313,10 @@ public Flux<ChatResponse> internalStream(Prompt prompt, ChatResponse previousCha
 									.build());
 						}
 						else {
+							// Reset tool choice to AUTO to prevent forcing repeated tool calls.
+							if (prompt.getOptions() instanceof DeepSeekChatOptions options) {
+								options.setToolChoice(ChatCompletionRequest.ToolChoiceBuilder.AUTO);
+							}
 							// Send the tool execution result back to the model.
 							return this.internalStream(new Prompt(toolExecutionResult.conversationHistory(), prompt.getOptions()),
 									response);

models/spring-ai-deepseek/src/test/java/org/springframework/ai/deepseek/DeepSeekChatModelToolChoiceResetTests.java

@@ -0,0 +1,115 @@
+/*
+ * Copyright 2023-2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.ai.deepseek;
+
+import java.time.Instant;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.junit.jupiter.api.Test;
+import org.mockito.ArgumentCaptor;
+
+import org.springframework.ai.chat.model.ChatResponse;
+import org.springframework.ai.chat.prompt.Prompt;
+import org.springframework.ai.deepseek.api.DeepSeekApi;
+import org.springframework.ai.deepseek.api.DeepSeekApi.ChatCompletion;
+import org.springframework.ai.deepseek.api.DeepSeekApi.ChatCompletion.Choice;
+import org.springframework.ai.deepseek.api.DeepSeekApi.ChatCompletionFinishReason;
+import org.springframework.ai.deepseek.api.DeepSeekApi.ChatCompletionMessage;
+import org.springframework.ai.deepseek.api.DeepSeekApi.ChatCompletionMessage.ChatCompletionFunction;
+import org.springframework.ai.deepseek.api.DeepSeekApi.ChatCompletionMessage.ToolCall;
+import org.springframework.ai.deepseek.api.DeepSeekApi.ChatCompletionRequest;
+import org.springframework.ai.tool.function.FunctionToolCallback;
+import org.springframework.http.ResponseEntity;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+/**
+ * Verifies that DeepSeekChatModel resets tool_choice to AUTO when resubmitting tool
+ * results (returnDirect=false) to avoid infinite tool call loops.
+ * @author Kuntal Maity
+ */
+class DeepSeekChatModelToolChoiceResetTests {
+
+	@Test
+	void resetsToolChoiceToAutoOnToolResultPushback() {
+		// Arrange: mock API to return a tool call first, then a normal assistant message
+		DeepSeekApi api = mock(DeepSeekApi.class);
+
+		// Capture requests to verify tool_choice on the second call
+		ArgumentCaptor<ChatCompletionRequest> reqCaptor = ArgumentCaptor.forClass(ChatCompletionRequest.class);
+
+		AtomicInteger apiCalls = new AtomicInteger(0);
+		when(api.chatCompletionEntity(reqCaptor.capture())).thenAnswer(invocation -> {
+			int call = apiCalls.incrementAndGet();
+			if (call == 1) {
+				// First response: model requests tool call
+				ChatCompletionMessage msg = new ChatCompletionMessage("", // content
+						ChatCompletionMessage.Role.ASSISTANT, null, null, List.of(new ToolCall("call_1", "function",
+								new ChatCompletionFunction("getMarineYetiDescription", "{}"))),
+						null, null);
+				ChatCompletion cc = new ChatCompletion("id-1",
+						List.of(new Choice(ChatCompletionFinishReason.TOOL_CALLS, 0, msg, null)),
+						Instant.now().getEpochSecond(), DeepSeekApi.ChatModel.DEEPSEEK_CHAT.getName(), null,
+						"chat.completion", null);
+				return ResponseEntity.ok(cc);
+			}
+			else {
+				// Second response: normal assistant message
+				ChatCompletionMessage msg = new ChatCompletionMessage("Marine yeti is orange.",
+						ChatCompletionMessage.Role.ASSISTANT, null, null, null, null, null);
+				ChatCompletion cc = new ChatCompletion("id-2",
+						List.of(new Choice(ChatCompletionFinishReason.STOP, 0, msg, null)),
+						Instant.now().getEpochSecond(), DeepSeekApi.ChatModel.DEEPSEEK_CHAT.getName(), null,
+						"chat.completion", null);
+				return ResponseEntity.ok(cc);
+			}
+		});
+
+		// Tool callback increments counter; returnDirect defaults to false
+		AtomicInteger toolInvocations = new AtomicInteger(0);
+		var tool = FunctionToolCallback.builder("getMarineYetiDescription", () -> {
+			toolInvocations.incrementAndGet();
+			return "Marine yeti is orange";
+		}).build();
+
+		DeepSeekChatOptions options = DeepSeekChatOptions.builder()
+			.model(DeepSeekApi.ChatModel.DEEPSEEK_CHAT)
+			.toolCallbacks(List.of(tool))
+			.toolChoice(ChatCompletionRequest.ToolChoiceBuilder.FUNCTION("getMarineYetiDescription"))
+			.build();
+
+		DeepSeekChatModel model = DeepSeekChatModel.builder().deepSeekApi(api).defaultOptions(options).build();
+
+		// Act
+		ChatResponse response = model.call(new Prompt("What is the color of a marine yeti?"));
+
+		// Assert: API was called twice (tool call, then final text)
+		assertThat(apiCalls.get()).isEqualTo(2);
+		// Second request tool_choice should be AUTO
+		assertThat(reqCaptor.getAllValues()).hasSize(2);
+		Object secondToolChoice = reqCaptor.getAllValues().get(1).toolChoice();
+		assertThat(secondToolChoice).isEqualTo(ChatCompletionRequest.ToolChoiceBuilder.AUTO);
+		// Tool executes exactly once
+		assertThat(toolInvocations.get()).isEqualTo(1);
+		// And final content is normal text
+		assertThat(response.getResult().getOutput().getText()).containsIgnoringCase("orange");
+	}
+
+}