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fix(core): handle pending tool calls when maxIters reached (#1005) #1012

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fix(core): handle pending tool calls when maxIters reached (#1005) #1012

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9f966d8
fix(core): handle pending tool calls when maxIters reached (#1005)
Fancy-hjyp Mar 21, 2026
c672315
style: apply spotless formatting
Fancy-hjyp Mar 21, 2026
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31 changes: 31 additions & 0 deletions agentscope-core/src/main/java/io/agentscope/core/ReActAgent.java
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Original file line number Diff line number Diff line change
Expand Up @@ -630,6 +630,37 @@ private Mono<PostActingEvent> notifyPostActingHook(
protected Mono<Msg> summarizing() {
log.debug("Maximum iterations reached. Generating summary...");

// Handle pending tool calls that were not completed before max iterations
if (hasPendingToolUse()) {
List<ToolUseBlock> pendingTools = extractPendingToolCalls();
log.warn(
"Max iterations reached with {} pending tool calls. Adding error results.",
pendingTools.size());

for (ToolUseBlock toolUse : pendingTools) {
ToolResultBlock errorResult =
ToolResultBlock.builder()
.id(toolUse.getId())
.output(
TextBlock.builder()
.text(
"Error: Tool execution cancelled because"
+ " maximum iterations limit ("
+ maxIters
+ ") was reached")
.build())
.build();

Msg errorResultMsg =
Msg.builder()
.name(getName())
.role(MsgRole.ASSISTANT)
.content(errorResult)
.build();
memory.addMessage(errorResultMsg);
}
}

List<Msg> messageList = prepareSummaryMessages();
GenerateOptions generateOptions = buildGenerateOptions();

Expand Down
166 changes: 166 additions & 0 deletions agentscope-core/src/test/java/io/agentscope/core/agent/ReActAgentSummarizingTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@
import io.agentscope.core.message.Msg;
import io.agentscope.core.message.MsgRole;
import io.agentscope.core.message.TextBlock;
import io.agentscope.core.message.ToolResultBlock;
import io.agentscope.core.message.ToolUseBlock;
import io.agentscope.core.model.ChatResponse;
import io.agentscope.core.model.ChatUsage;
Expand Down Expand Up @@ -397,4 +398,169 @@ void testSummaryAddedToMemory() {
assertEquals(
MsgRole.ASSISTANT, lastMessage.getRole(), "Summary message should be ASSISTANT");
}

@Test
@DisplayName("Should handle second call after maxIters with pending tool calls - Issue #1005")
void testSecondCallAfterMaxItersWithPendingToolCalls() {
// This test reproduces the bug reported in Issue #1005:
// 1. User has multi-round conversation with tool call
// 2. Tool doesn't respond (or times out), leaving pending tool calls
// 3. maxIters is reached, session auto-ends
// 4. User sends new message -> Should NOT throw IllegalStateException

InMemoryMemory memory = new InMemoryMemory();
final String toolId = "call_638e428da2cf48ceb8b05762";

// Mock model that returns a tool call on first call, then summary
final int[] callCount = {0};
MockModel mockModel =
new MockModel(
messages -> {
int callNum = callCount[0]++;
if (callNum == 0) {
// First call: return tool use block (simulating tool call)
return List.of(
ChatResponse.builder()
.id("msg_0")
.content(
List.of(
ToolUseBlock.builder()
.name("search_tool")
.id(toolId)
.input(
Map.of(
"query",
"test"))
.build()))
.usage(new ChatUsage(10, 20, 30))
.build());
} else {
// Second call: summarizing (because maxIters=1 reached)
return List.of(
ChatResponse.builder()
.id("msg_summary")
.content(
List.of(
TextBlock.builder()
.text(
"I reached the"
+ " maximum"
+ " iteration"
+ " limit."
+ " Please try"
+ " again.")
.build()))
.usage(new ChatUsage(10, 20, 30))
.build());
}
});

MockToolkit mockToolkit = new MockToolkit();

// Create agent with maxIters=1 to quickly trigger summarizing
ReActAgent agent =
ReActAgent.builder()
.name("TestAgent")
.sysPrompt("You are a helpful assistant.")
.model(mockModel)
.toolkit(mockToolkit)
.memory(memory)
.maxIters(1)
.build();

// First user message - triggers tool call and maxIters summarizing
Msg firstUserMsg = TestUtils.createUserMessage("User", "Please search for something");
Msg firstResponse =
agent.call(firstUserMsg)
.block(Duration.ofMillis(TestConstants.DEFAULT_TEST_TIMEOUT_MS));

// Verify first response
assertNotNull(firstResponse, "First response should not be null");
assertEquals(MsgRole.ASSISTANT, firstResponse.getRole());

// CRITICAL: Verify that the pending tool call has been resolved in memory
// Before the fix, memory would have pending tool calls without results
// After the fix, summarizing() should add error results for pending tools
List<Msg> memoryMessages = memory.getMessages();

// Find if there's a tool result message for the pending tool
boolean hasToolResultForPendingTool =
memoryMessages.stream()
.flatMap(m -> m.getContentBlocks(ToolResultBlock.class).stream())
.anyMatch(tr -> tr.getId() != null && tr.getId().equals(toolId));

assertTrue(
hasToolResultForPendingTool,
"Memory should contain error result for pending tool call after summarizing");

// Verify the tool result indicates cancellation due to max iterations
ToolResultBlock toolResult =
memoryMessages.stream()
.flatMap(m -> m.getContentBlocks(ToolResultBlock.class).stream())
.filter(tr -> tr.getId() != null && tr.getId().equals(toolId))
.findFirst()
.orElse(null);

// Tool result should be present (either from toolkit or from summarizing fix)
assertNotNull(toolResult);

// SECOND CALL - This is the critical test for Issue #1005
// Before the fix, this would throw:
// IllegalStateException: Cannot add messages without tool results when pending tool calls
// exist

// Reset model for second user interaction
final int[] secondCallCount = {0};
MockModel secondMockModel =
new MockModel(
messages -> {
int callNum = secondCallCount[0]++;
if (callNum == 0) {
return List.of(
ChatResponse.builder()
.id("msg_second_0")
.content(
List.of(
TextBlock.builder()
.text(
"Hello! How can I"
+ " help you"
+ " today?")
.build()))
.usage(new ChatUsage(5, 10, 15))
.build());
}
return List.of();
});

ReActAgent secondAgent =
ReActAgent.builder()
.name("TestAgent")
.sysPrompt("You are a helpful assistant.")
.model(secondMockModel)
.toolkit(mockToolkit)
.memory(memory) // Same memory
.maxIters(2)
.build();

// Second user message - this would throw IllegalStateException before the fix
Msg secondUserMsg = TestUtils.createUserMessage("User", "Hello again");

// This should NOT throw: "Cannot add messages without tool results when pending tool calls
// exist"
Msg secondResponse =
secondAgent
.call(secondUserMsg)
.block(Duration.ofMillis(TestConstants.DEFAULT_TEST_TIMEOUT_MS));

// Verify second response succeeded
assertNotNull(secondResponse, "Second response should not be null");
assertEquals(MsgRole.ASSISTANT, secondResponse.getRole());
assertTrue(
secondResponse.getFirstContentBlock() instanceof TextBlock,
"Second response should contain TextBlock");

TextBlock secondText = (TextBlock) secondResponse.getFirstContentBlock();
assertEquals("Hello! How can I help you today?", secondText.getText());
}
}
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