코드 탭 첫 LLM 응답 대기 진단을 강화하고 heartbeat 상태를 노출한다

설치형 환경에서 Code 탭 작업이 오래 걸릴 때 첫 도구 호출 전에 정체되는 구간을 추적할 수 있도록 StreamingToolExecutionCoordinator에 대기 heartbeat와 첫 응답 수신 로그를 추가했다.

첫 응답 전에는 모델 요청 시작, 응답 대기 시간, 첫 응답 수신 시점을 AgentLoopWait 로그와 Thinking 이벤트로 남기고, 이후 응답 지연도 heartbeat로 표시하도록 조정했다. 함께 StreamingToolExecutionCoordinatorTests를 추가해 첫 응답 지연 시 heartbeat가 노출되는 경로와 빠른 응답 시 불필요한 heartbeat가 생기지 않는 경로를 고정했다.

README.md와 docs/DEVELOPMENT.md에 2026-04-15 14:55 (KST) 기준 이력을 반영했고, dotnet build src/AxCopilot/AxCopilot.csproj -c Release -v minimal -p:OutputPath=bin\\verify_llm_wait_diag\\ -p:IntermediateOutputPath=obj\\verify_llm_wait_diag\\ 경고 0/오류 0, dotnet test src/AxCopilot.Tests/AxCopilot.Tests.csproj -c Release -v minimal --filter "StreamingToolExecutionCoordinatorTests|AgentLoopLlmRequestPreparationServiceTests|AgentLoopIterationPreparationServiceTests" -p:OutputPath=bin\\verify_llm_wait_diag_tests\\ -p:IntermediateOutputPath=obj\\verify_llm_wait_diag_tests\\ 통과 6을 확인했다.

src/AxCopilot/Services/Agent/StreamingToolExecutionCoordinator.cs

@@ -25,6 +25,8 @@ internal sealed class StreamingToolExecutionCoordinator : IToolExecutionCoordina
     private readonly Func<List<ChatMessage>, bool> _forceContextRecovery;
     private readonly Func<Exception, bool> _isTransientLlmError;
     private readonly Func<int, Exception, int> _computeTransientBackoffDelayMs;
+    private readonly TimeSpan _firstResponseHeartbeatDelay;
+    private readonly TimeSpan _responseHeartbeatInterval;
 
     public StreamingToolExecutionCoordinator(
         ILlmService llm,
@@ -34,7 +36,9 @@ internal sealed class StreamingToolExecutionCoordinator : IToolExecutionCoordina
         Func<string?, bool> isContextOverflowError,
         Func<List<ChatMessage>, bool> forceContextRecovery,
         Func<Exception, bool> isTransientLlmError,
-        Func<int, Exception, int> computeTransientBackoffDelayMs)
+        Func<int, Exception, int> computeTransientBackoffDelayMs,
+        TimeSpan? firstResponseHeartbeatDelay = null,
+        TimeSpan? responseHeartbeatInterval = null)
     {
         _llm = llm;
         _resolveRequestedToolName = resolveRequestedToolName;
@@ -44,6 +48,8 @@ internal sealed class StreamingToolExecutionCoordinator : IToolExecutionCoordina
         _forceContextRecovery = forceContextRecovery;
         _isTransientLlmError = isTransientLlmError;
         _computeTransientBackoffDelayMs = computeTransientBackoffDelayMs;
+        _firstResponseHeartbeatDelay = firstResponseHeartbeatDelay ?? TimeSpan.FromSeconds(8);
+        _responseHeartbeatInterval = responseHeartbeatInterval ?? TimeSpan.FromSeconds(15);
     }
 
     public async Task<ToolPrefetchResult?> TryPrefetchReadOnlyToolAsync(
@@ -105,8 +111,51 @@ internal sealed class StreamingToolExecutionCoordinator : IToolExecutionCoordina
 
                 var blocks = new List<ContentBlock>();
                 var textBuilder = new StringBuilder();
-                await foreach (var evt in _llm.StreamWithToolsAsync(messages, tools, forceToolCall, prefetchToolCallAsync, ct).WithCancellation(ct))
+                var (service, model) = _llm.GetCurrentModelInfo();
+                LogService.Info(
+                    $"[AgentLoopWait] {phaseLabel}: LLM 요청 시작 (service={service}, model={model}, messages={messages.Count}, tools={tools.Count}, forceToolCall={forceToolCall})");
+                _emitEvent(AgentEventType.Thinking, "", $"{phaseLabel}: 모델에 요청하는 중입니다...");
+
+                var waitStopwatch = Stopwatch.StartNew();
+                var firstEventReceived = false;
+                var nextHeartbeatAt = _firstResponseHeartbeatDelay;
+
+                await using var stream = _llm
+                    .StreamWithToolsAsync(messages, tools, forceToolCall, prefetchToolCallAsync, ct)
+                    .GetAsyncEnumerator(ct);
+
+                while (true)
                 {
+                    var moveNextTask = stream.MoveNextAsync().AsTask();
+                    while (!moveNextTask.IsCompleted)
+                    {
+                        var remaining = nextHeartbeatAt - waitStopwatch.Elapsed;
+                        if (remaining < TimeSpan.Zero)
+                            remaining = TimeSpan.Zero;
+
+                        var delayTask = Task.Delay(remaining, ct);
+                        var completedTask = await Task.WhenAny(moveNextTask, delayTask).ConfigureAwait(false);
+                        if (completedTask == moveNextTask)
+                            break;
+
+                        var waited = waitStopwatch.Elapsed;
+                        EmitWaitHeartbeat(phaseLabel, waited, firstEventReceived);
+                        nextHeartbeatAt = waited + _responseHeartbeatInterval;
+                    }
+
+                    if (!await moveNextTask.ConfigureAwait(false))
+                        break;
+
+                    var evt = stream.Current;
+                    if (!firstEventReceived)
+                    {
+                        firstEventReceived = true;
+                        LogService.Info(
+                            $"[AgentLoopWait] {phaseLabel}: 첫 응답 수신 ({waitStopwatch.ElapsedMilliseconds}ms, kind={evt.Kind})");
+                        if (waitStopwatch.Elapsed >= _firstResponseHeartbeatDelay)
+                            _emitEvent(AgentEventType.Thinking, "", $"{phaseLabel}: 모델 첫 응답을 받아 계속 진행합니다.");
+                    }
+
                     await onStreamEventAsync(evt);
                     if (evt.Kind == ToolStreamEventKind.TextDelta && !string.IsNullOrWhiteSpace(evt.Text))
                     {
@@ -170,4 +219,14 @@ internal sealed class StreamingToolExecutionCoordinator : IToolExecutionCoordina
             }
         }
     }
+
+    private void EmitWaitHeartbeat(string phaseLabel, TimeSpan waited, bool firstEventReceived)
+    {
+        var seconds = Math.Max(1, (int)Math.Round(waited.TotalSeconds));
+        var summary = firstEventReceived
+            ? $"{phaseLabel}: 모델 응답이 길어져 계속 기다리는 중입니다... ({seconds}초)"
+            : $"{phaseLabel}: 모델 첫 응답을 기다리는 중입니다... ({seconds}초)";
+        LogService.Info($"[AgentLoopWait] {summary}");
+        _emitEvent(AgentEventType.Thinking, "", summary);
+    }
 }