코드탭 tool trace 사전 정규화와 인코딩 정리 적용

- AgentMessageInvariantHelper에 전송 직전 structured tool trace 정규화 로직을 추가해 missing tool_result assistant와 orphan tool_result를 plain transcript로 평탄화함

- AgentLoopLlmRequestPreparationService에서 query view를 clone한 뒤 normalization을 적용하고 query_context 로그에 tool_trace_repair 메타를 남기도록 확장함

- SessionLearningCollector와 AgentLoopDiagnosticsFormatter의 깨진 문자열과 주석을 영어 기준으로 정리해 active Code 경로의 mojibake 노출을 줄임

- AgentMessageInvariantHelperTests, AgentLoopLlmRequestPreparationServiceTests를 보강하고 dotnet build 및 targeted dotnet test(34 통과, 경고/오류 0)로 검증함

README.md

@@ -2389,3 +2389,28 @@ MIT License
 - 검증:
   - `dotnet build src/AxCopilot/AxCopilot.csproj -c Release -v minimal -p:OutputPath=bin\\verify_context_reliability_full\\ -p:IntermediateOutputPath=obj\\verify_context_reliability_full\\` 경고 0 / 오류 0
   - `dotnet test src/AxCopilot.Tests/AxCopilot.Tests.csproj -c Release -v minimal --filter "AgentQueryContextBuilderTests|AgentToolResultBudgetTests|AgentLoopIterationPreparationServiceTests|AgentLoopLlmRequestPreparationServiceTests|CodeTaskWorkingSetServiceTests|AgentLoopCodeQualityTests" -p:OutputPath=bin\\verify_context_reliability_full_tests\\ -p:IntermediateOutputPath=obj\\verify_context_reliability_full_tests\\` 통과 150
+- 업데이트: 2026-04-16 01:57 (KST)
+- Code 탭 컨텍스트 신뢰성 보강 2차 작업을 반영했습니다.
+  - `src/AxCopilot/Services/Agent/AgentMessageInvariantHelper.cs`
+    - 전송 직전 `tool_use/tool_result` 이력을 다시 검사하는 `NormalizeHistoricalToolTrace(...)`를 추가했습니다.
+    - 결과가 없는 structured assistant tool-call은 plain assistant transcript로 평탄화하고, 대응 assistant가 없는 `tool_result`는 plain user transcript로 바꿔 request payload 자체가 더 일관된 상태로 나가도록 조정했습니다.
+  - `src/AxCopilot/Services/Agent/AgentLoopLlmRequestPreparationService.cs`
+    - query view를 그대로 참조하지 않고 deep clone한 뒤 tool-trace normalization을 적용하도록 바꿨습니다.
+    - supplemental message도 clone해서 원본 대화 이력을 직접 변형하지 않도록 했습니다.
+    - normalization 결과(`flattened structured assistant`, `converted orphan tool_result`)를 preparation result에 함께 남깁니다.
+  - `src/AxCopilot/Services/Agent/AgentLoopContextReliability.cs`
+    - `query_context` workflow log에 `tool_trace_repair=assistants:X/orphan_results:Y`를 추가해, 전송 직전 어떤 보정이 들어갔는지 실행 단위로 추적 가능하게 했습니다.
+  - `src/AxCopilot/Services/Agent/AgentLoopDiagnosticsFormatter.cs`
+    - active Code 경로에서 보이던 깨진 컨텍스트 압축 완료 문구를 영어 기준으로 정리했습니다.
+  - `src/AxCopilot/Services/Agent/SessionLearningCollector.cs`
+    - 주석과 주입 메시지, 학습 추출 요약 문자열을 영어 기준으로 전면 정리해 인코딩 손상 시에도 깨진 문자열이 다시 노출되지 않게 했습니다.
+- 테스트:
+  - `src/AxCopilot.Tests/Services/AgentMessageInvariantHelperTests.cs`
+    - missing tool-result가 있는 structured assistant flatten
+    - orphan `tool_result` plain transcript 변환
+    - valid structured tool pair 보존
+  - `src/AxCopilot.Tests/Services/AgentLoopLlmRequestPreparationServiceTests.cs`
+    - request preparation 단계가 broken tool trace를 normalize하면서도 원본 query messages는 보존하는지 검증
+- 검증:
+  - `dotnet build src/AxCopilot/AxCopilot.csproj -c Release -v minimal -p:OutputPath=bin\\verify_tool_trace_hardening\\ -p:IntermediateOutputPath=obj\\verify_tool_trace_hardening\\` 경고 0 / 오류 0
+  - `dotnet test src/AxCopilot.Tests/AxCopilot.Tests.csproj -c Release -v minimal --filter "AgentMessageInvariantHelperTests|AgentLoopLlmRequestPreparationServiceTests|AgentQueryContextBuilderTests|CodeTaskWorkingSetServiceTests|AgentLoopE2ETests" -p:OutputPath=bin\\verify_tool_trace_hardening_tests\\ -p:IntermediateOutputPath=obj\\verify_tool_trace_hardening_tests\\` 통과 34

docs/CODE_CONTEXT_RELIABILITY_PLAN.md

@@ -272,3 +272,19 @@ Updated: 2026-04-16 01:41 (KST)
 - Remaining follow-up:
   - extend pre-request tool-trace validation so the flattening/orphan repair count trends toward zero rather than being logged after repair
   - replace more mojibake prompt/status strings in active Code execution paths with English equivalents
+
+Updated: 2026-04-16 01:57 (KST)
+
+- Delivered in this pass:
+  - Phase 4 partial delivery:
+    - `AgentMessageInvariantHelper.cs` now normalizes historical tool traces before the request leaves the agent loop.
+    - structured assistant tool-call messages without matching `tool_result` now flatten into plain assistant transcript text.
+    - orphan `tool_result` messages now flatten into plain user transcript text instead of relying only on late OpenAI payload repair.
+    - `AgentLoopLlmRequestPreparationService.cs` clones the query window first, then applies normalization, so request cleanup does not mutate stored conversation history.
+    - `AgentLoopContextReliability.cs` now logs tool-trace repair counts inside the `query_context` transition for run-by-run observability.
+  - Phase 5 partial delivery:
+    - `SessionLearningCollector.cs` was rewritten with English-only comments and English injection text.
+    - `AgentLoopDiagnosticsFormatter.cs` no longer emits mojibake-prone compaction status text in active Code paths.
+- Remaining follow-up:
+  - measure whether `tool_trace_repair` counts keep trending down in long Code runs after this preflight normalization
+  - continue replacing older mojibake strings outside the active Code execution path

docs/DEVELOPMENT.md

@@ -1804,3 +1804,29 @@ UI ?遺우쁽????域뱀뮆???귐뗫솯?醫딆춦 ???袁る퓮 ?臾믩씜 ??疫
 - 검증:
   - `dotnet build src/AxCopilot/AxCopilot.csproj -c Release -v minimal -p:OutputPath=bin\\verify_context_reliability_full\\ -p:IntermediateOutputPath=obj\\verify_context_reliability_full\\` 경고 0 / 오류 0
   - `dotnet test src/AxCopilot.Tests/AxCopilot.Tests.csproj -c Release -v minimal --filter "AgentQueryContextBuilderTests|AgentToolResultBudgetTests|AgentLoopIterationPreparationServiceTests|AgentLoopLlmRequestPreparationServiceTests|CodeTaskWorkingSetServiceTests|AgentLoopCodeQualityTests" -p:OutputPath=bin\\verify_context_reliability_full_tests\\ -p:IntermediateOutputPath=obj\\verify_context_reliability_full_tests\\` 통과 150
+
+업데이트: 2026-04-16 01:57 (KST)
+- Code 탭 컨텍스트 신뢰성 보강 2차 작업을 적용했습니다.
+  - `src/AxCopilot/Services/Agent/AgentMessageInvariantHelper.cs`
+    - `NormalizeHistoricalToolTrace(...)`를 추가했습니다.
+    - 결과가 없는 structured assistant tool-call은 plain assistant transcript로 바꾸고, 대응 assistant가 없는 `tool_result`는 plain user transcript로 바꿔 request payload가 더 일관된 상태로 전송되도록 조정했습니다.
+  - `src/AxCopilot/Services/Agent/AgentLoopLlmRequestPreparationService.cs`
+    - query view를 deep clone한 뒤 normalization을 적용하도록 변경했습니다.
+    - supplemental messages도 clone해서 원본 대화 이력 오염 없이 request 직전 정리를 수행합니다.
+    - preparation result에 `FlattenedStructuredAssistantCount`, `ConvertedOrphanToolResultCount`를 추가했습니다.
+  - `src/AxCopilot/Services/Agent/AgentLoopContextReliability.cs`
+    - `query_context` workflow log에 `tool_trace_repair=assistants:X/orphan_results:Y`를 남기도록 확장했습니다.
+  - `src/AxCopilot/Services/Agent/AgentLoopDiagnosticsFormatter.cs`
+    - active Code 경로에서 보이던 깨진 compaction 상태 문자열을 영어 기준으로 정리했습니다.
+  - `src/AxCopilot/Services/Agent/SessionLearningCollector.cs`
+    - 영어 주석 기준으로 전면 정리했고, 학습 주입 메시지와 추출 요약 문자열도 영어 기준으로 통일했습니다.
+- 테스트:
+  - `src/AxCopilot.Tests/Services/AgentMessageInvariantHelperTests.cs`
+    - missing tool-result가 있는 structured assistant flatten
+    - orphan `tool_result` plain transcript 변환
+    - valid tool pair 보존
+  - `src/AxCopilot.Tests/Services/AgentLoopLlmRequestPreparationServiceTests.cs`
+    - preparation 단계 normalization 적용과 원본 query message 보존을 검증
+- 검증:
+  - `dotnet build src/AxCopilot/AxCopilot.csproj -c Release -v minimal -p:OutputPath=bin\\verify_tool_trace_hardening\\ -p:IntermediateOutputPath=obj\\verify_tool_trace_hardening\\` 경고 0 / 오류 0
+  - `dotnet test src/AxCopilot.Tests/AxCopilot.Tests.csproj -c Release -v minimal --filter "AgentMessageInvariantHelperTests|AgentLoopLlmRequestPreparationServiceTests|AgentQueryContextBuilderTests|CodeTaskWorkingSetServiceTests|AgentLoopE2ETests" -p:OutputPath=bin\\verify_tool_trace_hardening_tests\\ -p:IntermediateOutputPath=obj\\verify_tool_trace_hardening_tests\\` 통과 34

src/AxCopilot.Tests/Services/AgentLoopLlmRequestPreparationServiceTests.cs

@@ -86,4 +86,34 @@ public class AgentLoopLlmRequestPreparationServiceTests
         result.SendMessages[1].MetaKind.Should().Be("code_working_set");
         result.SendMessages.Last().Content.Should().Contain("[TOOL_REQUIRED]");
     }
+
+    [Fact]
+    public void Prepare_ShouldNormalizeBrokenHistoricalToolTraceBeforeSend()
+    {
+        var queryMessages = new List<ChatMessage>
+        {
+            new()
+            {
+                Role = "assistant",
+                Content = """{"_tool_use_blocks":[{"type":"text","text":"Inspecting source"},{"type":"tool_use","id":"call-missing","name":"file_read","input":{"path":"App.xaml"}}]}"""
+            },
+            new()
+            {
+                Role = "user",
+                Content = "fix the latest build failure"
+            }
+        };
+
+        var result = AgentLoopLlmRequestPreparationService.Prepare(
+            queryMessages,
+            totalToolCalls: 1,
+            forceInitialToolCallEnabled: true,
+            injectPreCallToolReminder: true,
+            noToolCallLoopRetry: 0);
+
+        result.FlattenedStructuredAssistantCount.Should().Be(1);
+        result.ConvertedOrphanToolResultCount.Should().Be(0);
+        result.SendMessages[0].Content.Should().Be("Inspecting source\n[previous tool call] file_read");
+        queryMessages[0].Content.Should().StartWith("{\"_tool_use_blocks\"");
+    }
 }

src/AxCopilot.Tests/Services/AgentMessageInvariantHelperTests.cs

@@ -7,6 +7,66 @@ namespace AxCopilot.Tests.Services;
 
 public class AgentMessageInvariantHelperTests
 {
+    [Fact]
+    public void NormalizeHistoricalToolTrace_ShouldFlattenAssistantWithMissingToolResult()
+    {
+        var messages = new List<ChatMessage>
+        {
+            new()
+            {
+                Role = "assistant",
+                Content = """{"_tool_use_blocks":[{"type":"text","text":"Reviewing the project"},{"type":"tool_use","id":"call-missing","name":"file_read","input":{"path":"App.xaml"}}]}"""
+            }
+        };
+
+        var result = AgentMessageInvariantHelper.NormalizeHistoricalToolTrace(messages);
+
+        result.FlattenedAssistantCount.Should().Be(1);
+        messages[0].Content.Should().Be("Reviewing the project\n[previous tool call] file_read");
+    }
+
+    [Fact]
+    public void NormalizeHistoricalToolTrace_ShouldConvertOrphanToolResultToPlainUserTranscript()
+    {
+        var messages = new List<ChatMessage>
+        {
+            new()
+            {
+                Role = "user",
+                Content = """{"type":"tool_result","tool_use_id":"call-orphan","tool_name":"file_read","content":"line1\nline2"}"""
+            }
+        };
+
+        var result = AgentMessageInvariantHelper.NormalizeHistoricalToolTrace(messages);
+
+        result.ConvertedOrphanToolResultCount.Should().Be(1);
+        messages[0].Content.Should().Be("[previous tool result: file_read]\nline1 line2");
+    }
+
+    [Fact]
+    public void NormalizeHistoricalToolTrace_ShouldPreserveValidStructuredToolPair()
+    {
+        var messages = new List<ChatMessage>
+        {
+            new()
+            {
+                Role = "assistant",
+                Content = """{"_tool_use_blocks":[{"type":"text","text":"Reading source"},{"type":"tool_use","id":"call-valid","name":"file_read","input":{"path":"App.xaml"}}]}"""
+            },
+            new()
+            {
+                Role = "user",
+                Content = """{"type":"tool_result","tool_use_id":"call-valid","tool_name":"file_read","content":"file content"}"""
+            }
+        };
+
+        var result = AgentMessageInvariantHelper.NormalizeHistoricalToolTrace(messages);
+
+        result.TotalAdjustedCount.Should().Be(0);
+        messages[0].Content.Should().StartWith("{\"_tool_use_blocks\"");
+        messages[1].Content.Should().StartWith("{\"type\":\"tool_result\"");
+    }
+
     [Fact]
     public void PopulateMissingToolResultPreviews_ShouldSynthesizePreview_WhenNoStoredPreviewExists()
     {

src/AxCopilot/Services/Agent/AgentLoopContextReliability.cs

@@ -14,6 +14,9 @@ public partial class AgentLoopService
     {
         var estimatedSendTokens = TokenEstimator.EstimateMessages(llmRequest.SendMessages);
         var workingSetSummary = codeWorkingSet?.DescribeForLog() ?? "none";
-        return $"{AgentLoopDiagnosticsFormatter.BuildQueryViewSummary(queryView)}, profile={queryView.ProfileName}, protected_recent={queryView.ProtectedRecentNonSystemMessages}, send={llmRequest.SendMessages.Count}, send_tokens={estimatedSendTokens}, supplemental={llmRequest.SupplementalMessageCount}, tool_reminder={llmRequest.InjectedToolReminder}, working_set={workingSetSummary}";
+        var toolTraceRepair = llmRequest.FlattenedStructuredAssistantCount > 0 || llmRequest.ConvertedOrphanToolResultCount > 0
+            ? $"tool_trace_repair=assistants:{llmRequest.FlattenedStructuredAssistantCount}/orphan_results:{llmRequest.ConvertedOrphanToolResultCount}, "
+            : "";
+        return $"{AgentLoopDiagnosticsFormatter.BuildQueryViewSummary(queryView)}, profile={queryView.ProfileName}, protected_recent={queryView.ProtectedRecentNonSystemMessages}, send={llmRequest.SendMessages.Count}, send_tokens={estimatedSendTokens}, supplemental={llmRequest.SupplementalMessageCount}, {toolTraceRepair}tool_reminder={llmRequest.InjectedToolReminder}, working_set={workingSetSummary}";
     }
 }

src/AxCopilot/Services/Agent/AgentLoopDiagnosticsFormatter.cs

@@ -6,8 +6,8 @@ internal static class AgentLoopDiagnosticsFormatter
     {
         var compactSummary = !string.IsNullOrWhiteSpace(result.StageSummary)
             ? result.StageSummary
-            : "기본";
-        return $"컨텍스트 압축 완료 — {compactSummary} · {Services.TokenEstimator.Format(result.SavedTokens)} tokens 절감";
+            : "default";
+        return $"Context compaction complete: {compactSummary}, saved {Services.TokenEstimator.Format(result.SavedTokens)} tokens";
     }
 
     public static string BuildQueryViewSummary(AgentQueryContextWindowResult queryView)

src/AxCopilot/Services/Agent/AgentLoopLlmRequestPreparationService.cs

@@ -6,7 +6,9 @@ internal sealed record AgentLoopLlmRequestPreparationResult(
     List<ChatMessage> SendMessages,
     bool ForceInitialToolCall,
     bool InjectedToolReminder,
-    int SupplementalMessageCount);
+    int SupplementalMessageCount,
+    int FlattenedStructuredAssistantCount,
+    int ConvertedOrphanToolResultCount);
 
 /// <summary>
 /// Builds the final LLM request array from the query window and optional
@@ -22,7 +24,8 @@ internal static class AgentLoopLlmRequestPreparationService
         int noToolCallLoopRetry,
         IEnumerable<ChatMessage>? supplementalMessages = null)
     {
-        var sendMessages = queryMessages.ToList();
+        var sendMessages = queryMessages.Select(CloneMessage).ToList();
+        var normalization = AgentMessageInvariantHelper.NormalizeHistoricalToolTrace(sendMessages);
         var supplementalCount = AppendSupplementalMessages(sendMessages, supplementalMessages);
         var forceInitialToolCall = totalToolCalls == 0 && forceInitialToolCallEnabled;
         if (!forceInitialToolCall
@@ -33,7 +36,9 @@ internal static class AgentLoopLlmRequestPreparationService
                 sendMessages,
                 forceInitialToolCall,
                 false,
-                supplementalCount);
+                supplementalCount,
+                normalization.FlattenedAssistantCount,
+                normalization.ConvertedOrphanToolResultCount);
         }
 
         sendMessages.Add(BuildToolReminderMessage());
@@ -41,7 +46,9 @@ internal static class AgentLoopLlmRequestPreparationService
             sendMessages,
             forceInitialToolCall,
             true,
-            supplementalCount);
+            supplementalCount,
+            normalization.FlattenedAssistantCount,
+            normalization.ConvertedOrphanToolResultCount);
     }
 
     internal static ChatMessage BuildToolReminderMessage()
@@ -65,10 +72,35 @@ internal static class AgentLoopLlmRequestPreparationService
             if (message == null || string.IsNullOrWhiteSpace(message.Content))
                 continue;
 
-            sendMessages.Add(message);
+            sendMessages.Add(CloneMessage(message));
             added++;
         }
 
         return added;
     }
+
+    private static ChatMessage CloneMessage(ChatMessage source)
+    {
+        return new ChatMessage
+        {
+            MsgId = source.MsgId,
+            Role = source.Role,
+            Content = source.Content,
+            Timestamp = source.Timestamp,
+            MetaKind = source.MetaKind,
+            MetaRunId = source.MetaRunId,
+            Feedback = source.Feedback,
+            ResponseElapsedMs = source.ResponseElapsedMs,
+            PromptTokens = source.PromptTokens,
+            CompletionTokens = source.CompletionTokens,
+            AttachedFiles = source.AttachedFiles?.ToList(),
+            QueryPreviewContent = source.QueryPreviewContent,
+            Images = source.Images?.Select(image => new ImageAttachment
+            {
+                Base64 = image.Base64,
+                MimeType = image.MimeType,
+                FileName = image.FileName,
+            }).ToList(),
+        };
+    }
 }

src/AxCopilot/Services/Agent/AgentMessageInvariantHelper.cs

@@ -4,7 +4,7 @@ using AxCopilot.Models;
 namespace AxCopilot.Services.Agent;
 
 /// <summary>
-/// tool_use / tool_result 불변식을 유지하기 위한 공용 helper입니다.
+/// Shared helpers for preserving valid tool-use / tool-result history.
 /// </summary>
 internal static class AgentMessageInvariantHelper
 {
@@ -16,6 +16,19 @@ internal static class AgentMessageInvariantHelper
         IReadOnlyDictionary<string, string> ExplicitByFingerprint,
         IReadOnlyDictionary<string, string> SyntheticByToolResultId);
 
+    internal sealed record StructuredAssistantToolUseSnapshot(
+        int MessageIndex,
+        string AssistantText,
+        IReadOnlyList<string> ToolNames,
+        IReadOnlyList<string> ToolIds);
+
+    public sealed record HistoricalToolTraceNormalizationResult(
+        int FlattenedAssistantCount,
+        int ConvertedOrphanToolResultCount)
+    {
+        public int TotalAdjustedCount => FlattenedAssistantCount + ConvertedOrphanToolResultCount;
+    }
+
     public static Dictionary<string, string> BuildToolResultPreviewMap(IEnumerable<ChatMessage>? messages)
     {
         var snapshot = BuildToolResultPreviewSnapshot(messages);
@@ -52,7 +65,9 @@ internal static class AgentMessageInvariantHelper
             if (!TryGetToolResultId(message, out var toolResultId)
                 || explicitById.ContainsKey(toolResultId)
                 || syntheticById.ContainsKey(toolResultId))
+            {
                 continue;
+            }
 
             if (TryGetToolResultFingerprint(message, out var fingerprint)
                 && explicitByFingerprint.ContainsKey(fingerprint))
@@ -71,6 +86,67 @@ internal static class AgentMessageInvariantHelper
         return new ToolResultPreviewSnapshot(explicitById, explicitByFingerprint, syntheticById);
     }
 
+    public static HistoricalToolTraceNormalizationResult NormalizeHistoricalToolTrace(IList<ChatMessage>? messages)
+    {
+        if (messages == null || messages.Count == 0)
+            return new HistoricalToolTraceNormalizationResult(0, 0);
+
+        var structuredAssistants = new List<StructuredAssistantToolUseSnapshot>();
+        var assistantIndexByToolUseId = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
+        var toolResultIds = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+
+        for (var i = 0; i < messages.Count; i++)
+        {
+            if (TryParseStructuredAssistantToolUse(messages[i], i, out var assistantSnapshot))
+            {
+                structuredAssistants.Add(assistantSnapshot);
+                foreach (var toolUseId in assistantSnapshot.ToolIds)
+                {
+                    if (!assistantIndexByToolUseId.ContainsKey(toolUseId))
+                        assistantIndexByToolUseId[toolUseId] = i;
+                }
+            }
+
+            if (TryGetToolResultId(messages[i], out var toolResultId))
+                toolResultIds.Add(toolResultId);
+        }
+
+        var flattenedAssistantCount = 0;
+        var flattenedToolUseIds = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+        foreach (var assistant in structuredAssistants)
+        {
+            if (assistant.ToolIds.Count == 0
+                || assistant.ToolIds.All(toolResultIds.Contains))
+            {
+                continue;
+            }
+
+            messages[assistant.MessageIndex].Content = BuildAssistantToolTranscript(assistant.AssistantText, assistant.ToolNames);
+            messages[assistant.MessageIndex].QueryPreviewContent = null;
+            flattenedAssistantCount++;
+            foreach (var toolUseId in assistant.ToolIds)
+                flattenedToolUseIds.Add(toolUseId);
+        }
+
+        var convertedOrphanToolResultCount = 0;
+        for (var i = 0; i < messages.Count; i++)
+        {
+            if (!TryGetToolResultId(messages[i], out var toolUseId))
+                continue;
+
+            var hasStructuredAssistant = assistantIndexByToolUseId.ContainsKey(toolUseId);
+            var wasFlattened = flattenedToolUseIds.Contains(toolUseId);
+            if (hasStructuredAssistant && !wasFlattened)
+                continue;
+
+            messages[i].Content = BuildToolResultTranscript(messages[i]);
+            messages[i].QueryPreviewContent = null;
+            convertedOrphanToolResultCount++;
+        }
+
+        return new HistoricalToolTraceNormalizationResult(flattenedAssistantCount, convertedOrphanToolResultCount);
+    }
+
     internal static bool TryResolveToolResultPreview(
         ChatMessage message,
         ToolResultPreviewSnapshot snapshot,
@@ -119,7 +195,9 @@ internal static class AgentMessageInvariantHelper
         if (snapshot.ExplicitByToolResultId.Count == 0
             && snapshot.ExplicitByFingerprint.Count == 0
             && snapshot.SyntheticByToolResultId.Count == 0)
+        {
             return false;
+        }
 
         var changed = false;
         foreach (var message in messages)
@@ -127,9 +205,7 @@ internal static class AgentMessageInvariantHelper
             if (!string.IsNullOrWhiteSpace(message.QueryPreviewContent))
                 continue;
             if (!TryResolveToolResultPreview(message, snapshot, out var preview))
-            {
                 continue;
-            }
 
             message.QueryPreviewContent = preview;
             changed = true;
@@ -382,6 +458,140 @@ internal static class AgentMessageInvariantHelper
         }
     }
 
+    private static bool TryParseStructuredAssistantToolUse(
+        ChatMessage message,
+        int messageIndex,
+        out StructuredAssistantToolUseSnapshot snapshot)
+    {
+        snapshot = null!;
+        if (!string.Equals(message.Role, "assistant", StringComparison.OrdinalIgnoreCase))
+            return false;
+
+        var content = message.Content ?? "";
+        if (!content.StartsWith("{\"_tool_use_blocks\"", StringComparison.Ordinal))
+            return false;
+
+        try
+        {
+            using var doc = JsonDocument.Parse(content);
+            if (!doc.RootElement.TryGetProperty("_tool_use_blocks", out var blocksEl) || blocksEl.ValueKind != JsonValueKind.Array)
+                return false;
+
+            var assistantTextParts = new List<string>();
+            var toolNames = new List<string>();
+            var toolIds = new List<string>();
+            foreach (var block in blocksEl.EnumerateArray())
+            {
+                if (!block.TryGetProperty("type", out var typeEl))
+                    continue;
+
+                var type = typeEl.GetString() ?? "";
+                if (string.Equals(type, "text", StringComparison.OrdinalIgnoreCase))
+                {
+                    var text = block.TryGetProperty("text", out var textEl)
+                        ? NormalizePreviewText(textEl.GetString() ?? "")
+                        : "";
+                    if (!string.IsNullOrWhiteSpace(text))
+                        assistantTextParts.Add(text);
+                    continue;
+                }
+
+                if (!string.Equals(type, "tool_use", StringComparison.OrdinalIgnoreCase))
+                    continue;
+
+                var toolName = block.TryGetProperty("name", out var toolNameEl)
+                    ? toolNameEl.GetString() ?? ""
+                    : "";
+                var toolId = block.TryGetProperty("id", out var toolIdEl)
+                    ? toolIdEl.GetString() ?? ""
+                    : "";
+
+                if (!string.IsNullOrWhiteSpace(toolName))
+                    toolNames.Add(toolName);
+                if (!string.IsNullOrWhiteSpace(toolId))
+                    toolIds.Add(toolId);
+            }
+
+            snapshot = new StructuredAssistantToolUseSnapshot(
+                messageIndex,
+                string.Join(" ", assistantTextParts),
+                toolNames,
+                toolIds);
+            return toolIds.Count > 0;
+        }
+        catch
+        {
+            return false;
+        }
+    }
+
+    private static string BuildAssistantToolTranscript(string assistantText, IReadOnlyList<string> toolNames)
+    {
+        var distinctNames = toolNames
+            .Where(name => !string.IsNullOrWhiteSpace(name))
+            .Distinct(StringComparer.OrdinalIgnoreCase)
+            .ToList();
+        var toolSummary = distinctNames.Count > 0
+            ? "[previous tool call] " + string.Join(", ", distinctNames)
+            : "[previous tool call]";
+
+        if (string.IsNullOrWhiteSpace(assistantText))
+            return toolSummary;
+
+        return assistantText + "\n" + toolSummary;
+    }
+
+    private static string BuildToolResultTranscript(ChatMessage message)
+    {
+        var toolName = "";
+        var previewText = "";
+
+        if (!string.IsNullOrWhiteSpace(message.QueryPreviewContent)
+            && TryParseToolResultPreviewPayload(message.QueryPreviewContent!, out var previewToolName, out var previewPayloadText))
+        {
+            toolName = previewToolName;
+            previewText = previewPayloadText;
+        }
+
+        if (string.IsNullOrWhiteSpace(previewText)
+            && TryParseToolResultPreviewPayload(message.Content ?? "", out var contentToolName, out var contentPayloadText))
+        {
+            toolName = string.IsNullOrWhiteSpace(toolName) ? contentToolName : toolName;
+            previewText = contentPayloadText;
+        }
+
+        if (string.IsNullOrWhiteSpace(previewText))
+            previewText = "tool result available";
+
+        var header = string.IsNullOrWhiteSpace(toolName)
+            ? "[previous tool result]"
+            : $"[previous tool result: {toolName}]";
+        return header + "\n" + previewText;
+    }
+
+    private static bool TryParseToolResultPreviewPayload(string payload, out string toolName, out string previewText)
+    {
+        toolName = "";
+        previewText = "";
+        if (string.IsNullOrWhiteSpace(payload))
+            return false;
+
+        try
+        {
+            using var doc = JsonDocument.Parse(payload);
+            var root = doc.RootElement;
+            toolName = root.TryGetProperty("tool_name", out var toolNameEl)
+                ? toolNameEl.GetString() ?? ""
+                : "";
+            previewText = ExtractPreviewText(root);
+            return !string.IsNullOrWhiteSpace(previewText);
+        }
+        catch
+        {
+            return false;
+        }
+    }
+
     private static string ExtractPreviewText(JsonElement root)
     {
         if (root.TryGetProperty("content", out var contentEl))

src/AxCopilot/Services/Agent/SessionLearningCollector.cs

@@ -4,8 +4,8 @@ using System.Text.RegularExpressions;
 namespace AxCopilot.Services.Agent;
 
 /// <summary>
-/// 에이전트 루프 실행 중 도구 결과에서 학습 포인트를 자동 추출하여
-/// 후속 반복에 컨텍스트로 주입하는 세션 내 단기 학습 수집기.
+/// Extracts small reusable learnings from tool outputs and injects them back
+/// into later turns as lightweight session memory.
 /// </summary>
 internal sealed class SessionLearningCollector
 {
@@ -13,24 +13,33 @@ internal sealed class SessionLearningCollector
     private readonly object _lock = new();
     private readonly int _maxLearnings;
 
-    /// <summary>도구 출력이 이 크기를 초과하면 앞부분만 사용하여 메모리 보호.</summary>
+    /// <summary>
+    /// Limits how much tool output is analyzed so memory extraction does not
+    /// over-allocate when a tool prints very large logs.
+    /// </summary>
     private const int MaxOutputAnalysisLength = 32_000;
 
     public SessionLearningCollector(int maxLearnings = 10)
         => _maxLearnings = maxLearnings;
 
-    public int Count { get { lock (_lock) return _learnings.Count; } }
+    public int Count
+    {
+        get
+        {
+            lock (_lock)
+                return _learnings.Count;
+        }
+    }
 
     /// <summary>
-    /// 도구 실행 결과에서 학습 포인트를 추출합니다.
-    /// 추출 규칙에 매칭되면 자동으로 저장됩니다.
+    /// Attempts to infer a reusable session learning from a tool result.
+    /// Matching learnings are stored automatically.
     /// </summary>
     public void TryExtract(string toolName, string toolOutput, bool success)
     {
         if (string.IsNullOrWhiteSpace(toolName) || string.IsNullOrWhiteSpace(toolOutput))
             return;
 
-        // 대용량 출력 보호: 앞부분만 분석 (Split('\n') 메모리 폭발 방지)
         var safeOutput = toolOutput.Length > MaxOutputAnalysisLength
             ? toolOutput[..MaxOutputAnalysisLength]
             : toolOutput;
@@ -57,21 +66,22 @@ internal sealed class SessionLearningCollector
         }
         catch
         {
-            // 추출 실패는 무시 — 학습 수집은 부수 효과
+            // Learning extraction must never break the main agent loop.
         }
 
-        if (learning is null) return;
+        if (learning is null)
+            return;
 
-        // 중복 방지: 동일 카테고리+내용이 이미 있으면 건너뜀
         lock (_lock)
         {
             if (_learnings.Any(l => l.Category == learning.Category
                 && l.Content.Equals(learning.Content, StringComparison.OrdinalIgnoreCase)))
+            {
                 return;
+            }
 
             _learnings.Add(learning);
 
-            // FIFO: 초과 시 가장 오래된 항목 일괄 제거 (RemoveAt(0) 반복 대비 O(n) → O(1))
             var excess = _learnings.Count - _maxLearnings;
             if (excess > 0)
                 _learnings.RemoveRange(0, excess);
@@ -79,122 +89,120 @@ internal sealed class SessionLearningCollector
     }
 
     /// <summary>
-    /// 현재 누적 학습을 시스템 메시지 형태로 포맷합니다.
-    /// 학습이 없으면 null을 반환합니다.
+    /// Builds the current learnings as an injection block. Returns null when
+    /// there is nothing to inject.
     /// </summary>
     public string? BuildInjectionMessage()
     {
         List<SessionLearning> snapshot;
         lock (_lock)
         {
-            if (_learnings.Count == 0) return null;
+            if (_learnings.Count == 0)
+                return null;
+
             snapshot = _learnings.ToList();
         }
 
         var sb = new StringBuilder();
-        sb.AppendLine("[System:SessionLearnings] 이 세션에서 자동 수집된 학습 사항:");
-        foreach (var l in snapshot)
-        {
-            sb.AppendLine($"- [{l.Category}] {l.Content}");
-        }
-        sb.AppendLine("위 내용을 참고하여 동일 실수를 반복하지 마세요.");
+        sb.AppendLine("[System:SessionLearnings] Reusable learnings collected in this session:");
+        foreach (var learning in snapshot)
+            sb.AppendLine($"- [{learning.Category}] {learning.Content}");
+        sb.AppendLine("Use these notes to avoid repeating the same failed attempts.");
         return sb.ToString().TrimEnd();
     }
 
-    /// <summary>모든 학습 초기화.</summary>
+    /// <summary>Clears all collected learnings.</summary>
     public void Clear()
     {
-        lock (_lock) _learnings.Clear();
+        lock (_lock)
+            _learnings.Clear();
     }
 
-    // ════════════════════════════════════════════════════════════
-    //  추출 규칙
-    // ════════════════════════════════════════════════════════════
+    // Extraction rules
 
-    /// <summary>빌드/테스트 실패에서 프로젝트 설정 학습.</summary>
+    /// <summary>Extracts project/build configuration hints from failed builds or tests.</summary>
     private static SessionLearning? ExtractBuildConfig(string tool, string output)
     {
         var sb = new StringBuilder();
 
-        // .NET 타겟 프레임워크 감지
         var tfmMatch = Regex.Match(output, @"net\d+\.\d+(?:-windows[\d.]*)?", RegexOptions.IgnoreCase);
         if (tfmMatch.Success)
-            sb.Append($"타겟: {tfmMatch.Value}");
+            sb.Append($"target={tfmMatch.Value}");
 
-        // 에러 코드 추출 (CS, TS, etc.)
         var errorCodes = Regex.Matches(output, @"\b(CS|TS|E)\d{4}\b");
         if (errorCodes.Count > 0)
         {
             var codes = errorCodes.Cast<Match>().Select(m => m.Value).Distinct().Take(5);
-            if (sb.Length > 0) sb.Append(", ");
-            sb.Append($"에러: {string.Join(", ", codes)}");
+            if (sb.Length > 0)
+                sb.Append(", ");
+            sb.Append($"errors={string.Join(", ", codes)}");
         }
 
-        // 빌드 시스템 감지
         if (output.Contains("MSBuild", StringComparison.OrdinalIgnoreCase))
         {
-            if (sb.Length > 0) sb.Append(", ");
-            sb.Append("빌드: MSBuild");
+            if (sb.Length > 0)
+                sb.Append(", ");
+            sb.Append("build=MSBuild");
         }
         else if (output.Contains("npm", StringComparison.OrdinalIgnoreCase)
             || output.Contains("node", StringComparison.OrdinalIgnoreCase))
         {
-            if (sb.Length > 0) sb.Append(", ");
-            sb.Append("빌드: npm/node");
+            if (sb.Length > 0)
+                sb.Append(", ");
+            sb.Append("build=npm/node");
         }
 
-        // 주요 에러 메시지 첫 줄 (Split 대신 라인별 스캔으로 메모리 절약)
         var errorLine = FindFirstMatchingLine(output,
-            l => l.Contains("error", StringComparison.OrdinalIgnoreCase)
-                && l.Length > 10 && l.Length < 200);
+            line => line.Contains("error", StringComparison.OrdinalIgnoreCase)
+                && line.Length > 10 && line.Length < 200);
         if (errorLine != null)
         {
-            if (sb.Length > 0) sb.Append(" — ");
+            if (sb.Length > 0)
+                sb.Append(" :: ");
             sb.Append(Truncate(errorLine, 120));
         }
 
         return sb.Length > 0
-            ? new("build_config", sb.ToString(), DateTime.Now, tool)
+            ? new SessionLearning("build_config", sb.ToString(), DateTime.Now, tool)
             : null;
     }
 
-    /// <summary>grep/glob 결과에서 코드 위치 패턴 학습.</summary>
+    /// <summary>Extracts repeated code-location patterns from grep or glob results.</summary>
     private static SessionLearning? ExtractCodeLocation(string tool, string output)
     {
-        // 파일 경로 추출
         var paths = Regex.Matches(output, @"(?:^|\s)([\w./\\-]+\.\w{1,6})(?:\s|:|$)", RegexOptions.Multiline)
             .Cast<Match>()
             .Select(m => m.Groups[1].Value)
-            .Where(p => p.Contains('/') || p.Contains('\\'))
+            .Where(path => path.Contains('/') || path.Contains('\\'))
             .Distinct(StringComparer.OrdinalIgnoreCase)
             .Take(5)
             .ToList();
 
-        if (paths.Count < 2) return null; // 단일 파일이면 학습 가치 낮음
+        if (paths.Count < 2)
+            return null;
 
-        // 공통 디렉토리 패턴 추출
         var dirs = paths
-            .Select(p => string.Join("/", p.Replace('\\', '/').Split('/').SkipLast(1)))
-            .Where(d => !string.IsNullOrEmpty(d))
-            .GroupBy(d => d)
-            .OrderByDescending(g => g.Count())
+            .Select(path => string.Join("/", path.Replace('\\', '/').Split('/').SkipLast(1)))
+            .Where(dir => !string.IsNullOrEmpty(dir))
+            .GroupBy(dir => dir)
+            .OrderByDescending(group => group.Count())
             .FirstOrDefault();
 
-        if (dirs == null) return null;
+        if (dirs == null)
+            return null;
 
-        var content = $"관련 파일이 {dirs.Key}/ 에 집중 ({paths.Count}개 파일)";
-        return new("code_location", content, DateTime.Now, tool);
+        var content = $"related files are clustered under {dirs.Key}/ ({paths.Count} files)";
+        return new SessionLearning("code_location", content, DateTime.Now, tool);
     }
 
-    /// <summary>프로젝트 메타 파일 읽기에서 구조 학습.</summary>
+    /// <summary>Extracts structure hints from project metadata files.</summary>
     private static SessionLearning? ExtractProjectStructure(string tool, string output)
     {
         var sb = new StringBuilder();
 
-        // csproj: TargetFramework, PackageReference
         var tfm = Regex.Match(output, @"<TargetFramework[s]?>(.*?)</TargetFramework[s]?>", RegexOptions.IgnoreCase);
         if (tfm.Success)
-            sb.Append($"프레임워크: {tfm.Groups[1].Value}");
+            sb.Append($"framework={tfm.Groups[1].Value}");
 
         var packages = Regex.Matches(output, @"<PackageReference\s+Include=""([^""]+)""", RegexOptions.IgnoreCase)
             .Cast<Match>()
@@ -203,62 +211,64 @@ internal sealed class SessionLearningCollector
             .ToList();
         if (packages.Count > 0)
         {
-            if (sb.Length > 0) sb.Append(", ");
-            sb.Append($"주요 패키지: {string.Join(", ", packages)}");
+            if (sb.Length > 0)
+                sb.Append(", ");
+            sb.Append($"packages={string.Join(", ", packages)}");
         }
 
-        // package.json: name, dependencies
         var pkgName = Regex.Match(output, @"""name""\s*:\s*""([^""]+)""");
         if (pkgName.Success)
         {
-            if (sb.Length > 0) sb.Append(", ");
-            sb.Append($"패키지: {pkgName.Groups[1].Value}");
+            if (sb.Length > 0)
+                sb.Append(", ");
+            sb.Append($"package={pkgName.Groups[1].Value}");
         }
 
         return sb.Length > 0
-            ? new("project_structure", Truncate(sb.ToString(), 200), DateTime.Now, tool)
+            ? new SessionLearning("project_structure", Truncate(sb.ToString(), 200), DateTime.Now, tool)
             : null;
     }
 
-    /// <summary>런타임 감지 결과에서 의존성 학습.</summary>
+    /// <summary>Extracts environment and dependency hints from environment detection.</summary>
     private static SessionLearning? ExtractDependency(string tool, string output)
     {
-        if (output.Length < 10) return null;
+        if (output.Length < 10)
+            return null;
 
-        // 주요 런타임/SDK 정보만 추출 (Split 대신 라인별 스캔)
         var lines = FindMatchingLines(output, 4,
-            l => l.Length > 5 && l.Length < 150
-                && (l.Contains("SDK", StringComparison.OrdinalIgnoreCase)
-                    || l.Contains("runtime", StringComparison.OrdinalIgnoreCase)
-                    || l.Contains("version", StringComparison.OrdinalIgnoreCase)
-                    || l.Contains("node", StringComparison.OrdinalIgnoreCase)
-                    || l.Contains("python", StringComparison.OrdinalIgnoreCase)));
+            line => line.Length > 5 && line.Length < 150
+                && (line.Contains("SDK", StringComparison.OrdinalIgnoreCase)
+                    || line.Contains("runtime", StringComparison.OrdinalIgnoreCase)
+                    || line.Contains("version", StringComparison.OrdinalIgnoreCase)
+                    || line.Contains("node", StringComparison.OrdinalIgnoreCase)
+                    || line.Contains("python", StringComparison.OrdinalIgnoreCase)));
 
-        if (lines.Count == 0) return null;
+        if (lines.Count == 0)
+            return null;
 
-        return new("dependency", string.Join("; ", lines), DateTime.Now, tool);
+        return new SessionLearning("dependency", string.Join("; ", lines), DateTime.Now, tool);
     }
 
-    /// <summary>파일 조작 실패에서 에러 패턴 학습.</summary>
+    /// <summary>Extracts a stable failure pattern from file operation errors.</summary>
     private static SessionLearning? ExtractErrorPattern(string tool, string output)
     {
-        if (output.Length < 10) return null;
+        if (output.Length < 10)
+            return null;
 
-        var firstLine = FindFirstMatchingLine(output, l => l.Length > 5);
-        if (firstLine == null) return null;
+        var firstLine = FindFirstMatchingLine(output, line => line.Length > 5);
+        if (firstLine == null)
+            return null;
 
-        return new("error_pattern", $"{tool}: {Truncate(firstLine, 150)}", DateTime.Now, tool);
+        return new SessionLearning("error_pattern", $"{tool}: {Truncate(firstLine, 150)}", DateTime.Now, tool);
     }
 
-    // ════════════════════════════════════════════════════════════
-    //  유틸
-    // ════════════════════════════════════════════════════════════
+    // Helpers
 
     private static bool IsProjectMetaFile(string output)
-        => output.Contains("<Project", StringComparison.OrdinalIgnoreCase)      // csproj
-        || output.Contains("\"dependencies\"", StringComparison.OrdinalIgnoreCase) // package.json
-        || output.Contains("[package]", StringComparison.OrdinalIgnoreCase)       // Cargo.toml
-        || output.Contains("\"name\":", StringComparison.OrdinalIgnoreCase);       // package.json
+        => output.Contains("<Project", StringComparison.OrdinalIgnoreCase)
+           || output.Contains("\"dependencies\"", StringComparison.OrdinalIgnoreCase)
+           || output.Contains("[package]", StringComparison.OrdinalIgnoreCase)
+           || output.Contains("\"name\":", StringComparison.OrdinalIgnoreCase);
 
     private static bool IsFileOperationTool(string tool)
         => tool is "file_write" or "file_edit" or "file_read" or "file_manage";
@@ -267,8 +277,8 @@ internal sealed class SessionLearningCollector
         => text.Length <= maxLen ? text : text[..maxLen] + "...";
 
     /// <summary>
-    /// Split('\n') 없이 라인별 스캔하여 첫 매칭 라인을 반환합니다.
-    /// 대용량 출력에서 전체 배열 할당을 방지합니다.
+    /// Scans line by line without allocating a full Split('\n') array and
+    /// returns the first matching line.
     /// </summary>
     private static string? FindFirstMatchingLine(string text, Func<string, bool> predicate)
     {
@@ -280,14 +290,17 @@ internal sealed class SessionLearningCollector
             var line = lineSpan.Trim().ToString();
             if (predicate(line))
                 return line;
-            if (newlineIdx < 0) break;
+            if (newlineIdx < 0)
+                break;
             span = span[(newlineIdx + 1)..];
         }
+
         return null;
     }
 
     /// <summary>
-    /// Split('\n') 없이 라인별 스캔하여 최대 maxCount개의 매칭 라인을 반환합니다.
+    /// Scans line by line without allocating a full Split('\n') array and
+    /// returns up to <paramref name="maxCount"/> matching lines.
     /// </summary>
     private static List<string> FindMatchingLines(string text, int maxCount, Func<string, bool> predicate)
     {
@@ -300,9 +313,11 @@ internal sealed class SessionLearningCollector
             var line = lineSpan.Trim().ToString();
             if (predicate(line))
                 results.Add(line);
-            if (newlineIdx < 0) break;
+            if (newlineIdx < 0)
+                break;
             span = span[(newlineIdx + 1)..];
         }
+
         return results;
     }
 }