safely merge empty tool call name case(streaming mode)

spring-ai-model/src/main/java/org/springframework/ai/model/tool/DefaultToolCallingManager.java

@@ -17,6 +17,7 @@
 package org.springframework.ai.model.tool;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -136,7 +137,7 @@ public ToolExecutionResult executeToolCalls(Prompt prompt, ChatResponse chatResp
 			throw new IllegalStateException("No tool call requested by the chat model");
 		}
 
-		AssistantMessage assistantMessage = toolCallGeneration.get().getOutput();
+		AssistantMessage assistantMessage = safelyMergeAssistantMessageIfEmptyToolCallPresent(toolCallGeneration);
 
 		ToolContext toolContext = buildToolContext(prompt, assistantMessage);
 
@@ -152,6 +153,35 @@ public ToolExecutionResult executeToolCalls(Prompt prompt, ChatResponse chatResp
 			.build();
 	}
 
+	private AssistantMessage safelyMergeAssistantMessageIfEmptyToolCallPresent(
+			Optional<Generation> toolCallGeneration) {
+		if (toolCallGeneration.isEmpty()) {
+			throw new IllegalStateException("No tool call requested by the chat model");
+		}
+		AssistantMessage assistantMessage = toolCallGeneration.get().getOutput();
+		List<AssistantMessage.ToolCall> toolCalls = assistantMessage.getToolCalls();
+		List<AssistantMessage.ToolCall> reversedToolCalls = new ArrayList<>(toolCalls);
+		Collections.reverse(reversedToolCalls);
+		List<AssistantMessage.ToolCall> newToolCalls = new ArrayList<>();
+		StringBuilder args = new StringBuilder();
+		for (AssistantMessage.ToolCall toolCall : reversedToolCalls) {
+			args.append(toolCall.arguments());
+			if (StringUtils.hasText(toolCall.name())) {
+				AssistantMessage.ToolCall newToolCall = new AssistantMessage.ToolCall(toolCall.id(), toolCall.type(),
+						toolCall.name(), args.toString());
+				newToolCalls.add(newToolCall);
+				args = new StringBuilder();
+			}
+		}
+		Collections.reverse(newToolCalls);
+		return AssistantMessage.builder()
+			.content(assistantMessage.getText())
+			.toolCalls(newToolCalls)
+			.media(assistantMessage.getMedia())
+			.properties(assistantMessage.getMetadata())
+			.build();
+	}
+
 	private static ToolContext buildToolContext(Prompt prompt, AssistantMessage assistantMessage) {
 		Map<String, Object> toolContextMap = Map.of();
 

spring-ai-model/src/test/java/org/springframework/ai/model/tool/DefaultToolCallingManagerTest.java

@@ -423,4 +423,59 @@ public String call(String toolInput) {
 		assertThatNoException().isThrownBy(() -> manager.executeToolCalls(prompt, chatResponse));
 	}
 
+	@Test
+	void shouldHandleMultipleGenerationsWithToolCallsWhenNameIsEmpty() {
+		ToolCallback toolCallback = new ToolCallback() {
+			@Override
+			public ToolDefinition getToolDefinition() {
+				return DefaultToolDefinition.builder()
+					.name("multiGenTool")
+					.description("Tool for multiple generations")
+					.inputSchema("{}")
+					.build();
+			}
+
+			@Override
+			public ToolMetadata getToolMetadata() {
+				return ToolMetadata.builder().build();
+			}
+
+			@Override
+			public String call(String toolInput) {
+				return "{\"result\": \"success\"}";
+			}
+		};
+
+		// Create multiple generations with tool calls
+		AssistantMessage.ToolCall toolCall1 = new AssistantMessage.ToolCall("1", "function", "multiGenTool", "{}");
+		AssistantMessage.ToolCall toolCall2 = new AssistantMessage.ToolCall("2", "function", "multiGenTool", "{}");
+		AssistantMessage.ToolCall toolCall3 = new AssistantMessage.ToolCall("3", "function", "", "{}");
+
+		AssistantMessage assistantMessage1 = AssistantMessage.builder()
+			.content("")
+			.properties(Map.of())
+			.toolCalls(List.of(toolCall1))
+			.build();
+
+		AssistantMessage assistantMessage2 = AssistantMessage.builder()
+			.content("")
+			.properties(Map.of())
+			.toolCalls(List.of(toolCall2, toolCall3))
+			.build();
+
+		Generation generation1 = new Generation(assistantMessage1);
+		Generation generation2 = new Generation(assistantMessage2);
+
+		ChatResponse chatResponse = new ChatResponse(List.of(generation1, generation2));
+
+		Prompt prompt = new Prompt(List.of(new UserMessage("test multiple generations")));
+
+		DefaultToolCallingManager manager = DefaultToolCallingManager.builder()
+			.observationRegistry(ObservationRegistry.NOOP)
+			.toolCallbackResolver(toolName -> "multiGenTool".equals(toolName) ? toolCallback : null)
+			.build();
+
+		assertThatNoException().isThrownBy(() -> manager.executeToolCalls(prompt, chatResponse));
+	}
+
 }