압축 경계에서도 tool pair 불변식을 유지하도록 보강

claw-code의 sessionMemoryCompact 흐름을 참고해 AX Agent가 recent window를 자를 때도 tool_use/tool_result 짝이 끊기지 않도록 보정 범위를 넓혔다.

- AgentMessageInvariantHelper를 추가해 tool_result와 assistant _tool_use_blocks 대응 관계를 공용 로직으로 정리

- AgentQueryContextBuilder는 공용 helper를 사용하도록 단순화

- ContextCondenser의 microcompact, session memory compact, snip, 요약 단계가 모두 같은 split helper로 recent window를 계산하도록 조정

- compaction split 시 recent window 안의 tool_result가 old window의 tool_use를 잃는 상황을 줄여 API pairing 안정성을 높임

- README.md, docs/DEVELOPMENT.md에 2026-04-12 21:39 (KST) 기준 이력 반영

검증: dotnet build src/AxCopilot/AxCopilot.csproj -c Release -v minimal -p:OutputPath=bin\\verify\\ -p:IntermediateOutputPath=obj\\verify\\ / 경고 0, 오류 0

README.md

@@ -1628,3 +1628,8 @@ MIT License
   - 같은 helper에서 `tool_result`가 남아 있는 kept range를 검사해, 대응되는 assistant `_tool_use_blocks`가 잘리지 않도록 window start를 뒤로 보정합니다.
   - [AgentLoopService.cs](/E:/AX%20Copilot%20-%20Codex/src/AxCopilot/Services/Agent/AgentLoopService.cs)는 각 반복에서 `messagesForQuery`에 해당하는 전송 뷰를 만든 뒤 `SendWithToolsWithRecoveryAsync()`와 텍스트 fallback 호출에 사용하도록 바꿨습니다.
   - [ContextCondenser.cs](/E:/AX%20Copilot%20-%20Codex/src/AxCopilot/Services/Agent/ContextCondenser.cs)는 `triggerPercent`만 보던 기준에서 `effective context window - output reserve - buffer` 개념을 반영해 자동 압축 시작 지점을 더 보수적으로 계산하도록 바꿨습니다.
+- 업데이트: 2026-04-12 21:39 (KST)
+  - `claw-code`의 `sessionMemoryCompact`처럼 압축 경계 자체에서도 `tool_use / tool_result` 짝이 끊기지 않도록 보정 범위를 넓혔습니다.
+  - [AgentMessageInvariantHelper.cs](/E:/AX%20Copilot%20-%20Codex/src/AxCopilot/Services/Agent/AgentMessageInvariantHelper.cs)를 추가해 `tool_result`가 남는 kept range에서 필요한 assistant `_tool_use_blocks`를 공용 로직으로 다시 포함시키게 했습니다.
+  - [ContextCondenser.cs](/E:/AX%20Copilot%20-%20Codex/src/AxCopilot/Services/Agent/ContextCondenser.cs)는 `MicrocompactOlderMessages`, `SessionMemoryCompactOlderMessages`, `CollapseAndSnipOlderMessages`, `SummarizeOldMessagesAsync`가 모두 같은 split helper를 사용하도록 바꿨습니다.
+  - 이제 recent window가 `tool_result`로 시작하는 경우에도, 그 결과를 참조하는 이전 `tool_use`가 요약/압축 쪽으로 잘려 나가 API pairing 오류를 만드는 상황을 줄일 수 있습니다.

docs/DEVELOPMENT.md

@@ -585,3 +585,17 @@ owKindCounts를 함께 남겨 %APPDATA%\\AxCopilot\\perf 기준으로 transcript
 - 부가 정리
   - `src/AxCopilot/Views/ChatWindow.ComposerQueuePresentation.cs`의 미사용 필드를 제거해 빌드 경고를 없앴습니다.
 
+## 압축 경계에서 tool pair 불변식 보정 확대 (2026-04-12 21:39 KST)
+
+- 전송 직전 query view에서만 pair를 보정하던 상태에서 한 단계 더 나아가, compact split 자체도 `tool_use / tool_result` 불변식을 보존하도록 정리했습니다.
+- `src/AxCopilot/Services/Agent/AgentMessageInvariantHelper.cs`
+  - `tool_result`에서 `tool_use_id`를 읽고, assistant `_tool_use_blocks`에서 대응 `tool_use`를 찾는 공용 helper를 추가했습니다.
+  - query view builder와 context condenser가 같은 보정 규칙을 공유하도록 맞췄습니다.
+- `src/AxCopilot/Services/Agent/ContextCondenser.cs`
+  - `SplitCompactionWindow()`를 추가해 recent window를 자를 때 `AgentMessageInvariantHelper.AdjustStartIndexForToolPairs()`를 먼저 적용합니다.
+  - `MicrocompactOlderMessages`, `SessionMemoryCompactOlderMessages`, `CollapseAndSnipOlderMessages`, `SummarizeOldMessagesAsync`가 모두 같은 split helper를 사용하게 바꿨습니다.
+  - 결과적으로 recent window 안에 `tool_result`가 남아 있는데 대응 `tool_use`는 old window로 밀려 요약/압축돼 버리는 상황을 줄였습니다.
+- 기대 효과
+  - 자동 압축 직후 다음 API 호출에서 orphan `tool_result`로 인한 pairing 오류가 줄어듭니다.
+  - query view 보정과 compaction split 보정이 같은 규칙을 쓰므로, 저장 상태와 전송 상태 사이의 불일치가 줄어듭니다.
+

src/AxCopilot/Services/Agent/AgentMessageInvariantHelper.cs

@@ -0,0 +1,122 @@
+using System.Text.Json;
+using AxCopilot.Models;
+
+namespace AxCopilot.Services.Agent;
+
+/// <summary>
+/// tool_use / tool_result 불변식을 유지하기 위한 공용 helper입니다.
+/// </summary>
+internal static class AgentMessageInvariantHelper
+{
+    public static int AdjustStartIndexForToolPairs(
+        IReadOnlyList<ChatMessage> messages,
+        int startIndex,
+        out int preservedToolPairs)
+    {
+        preservedToolPairs = 0;
+        if (startIndex <= 0)
+            return startIndex;
+
+        var toolResultIds = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+        for (var i = startIndex; i < messages.Count; i++)
+        {
+            if (TryGetToolResultId(messages[i], out var toolResultId))
+                toolResultIds.Add(toolResultId);
+        }
+
+        if (toolResultIds.Count == 0)
+            return startIndex;
+
+        var toolUseIdsInWindow = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+        for (var i = startIndex; i < messages.Count; i++)
+        {
+            foreach (var toolUseId in EnumerateToolUseIds(messages[i]))
+                toolUseIdsInWindow.Add(toolUseId);
+        }
+
+        toolResultIds.ExceptWith(toolUseIdsInWindow);
+        if (toolResultIds.Count == 0)
+            return startIndex;
+
+        var adjustedStart = startIndex;
+        for (var i = startIndex - 1; i >= 0 && toolResultIds.Count > 0; i--)
+        {
+            var foundAny = false;
+            foreach (var toolUseId in EnumerateToolUseIds(messages[i]))
+            {
+                if (!toolResultIds.Remove(toolUseId))
+                    continue;
+
+                preservedToolPairs++;
+                foundAny = true;
+            }
+
+            if (foundAny)
+                adjustedStart = i;
+        }
+
+        return adjustedStart;
+    }
+
+    public static bool TryGetToolResultId(ChatMessage message, out string toolResultId)
+    {
+        toolResultId = "";
+        if (!string.Equals(message.Role, "user", StringComparison.OrdinalIgnoreCase))
+            return false;
+
+        var content = message.Content ?? "";
+        if (!content.StartsWith("{\"type\":\"tool_result\"", StringComparison.Ordinal))
+            return false;
+
+        try
+        {
+            using var doc = JsonDocument.Parse(content);
+            toolResultId = doc.RootElement.TryGetProperty("tool_use_id", out var idEl)
+                ? idEl.GetString() ?? ""
+                : "";
+            return !string.IsNullOrWhiteSpace(toolResultId);
+        }
+        catch
+        {
+            return false;
+        }
+    }
+
+    public static IEnumerable<string> EnumerateToolUseIds(ChatMessage message)
+    {
+        if (!string.Equals(message.Role, "assistant", StringComparison.OrdinalIgnoreCase))
+            yield break;
+
+        var content = message.Content ?? "";
+        if (!content.StartsWith("{\"_tool_use_blocks\"", StringComparison.Ordinal))
+            yield break;
+
+        JsonDocument? doc = null;
+        try
+        {
+            doc = JsonDocument.Parse(content);
+            if (!doc.RootElement.TryGetProperty("_tool_use_blocks", out var blocksEl) || blocksEl.ValueKind != JsonValueKind.Array)
+                yield break;
+
+            foreach (var block in blocksEl.EnumerateArray())
+            {
+                if (!block.TryGetProperty("type", out var typeEl)
+                    || !string.Equals(typeEl.GetString(), "tool_use", StringComparison.OrdinalIgnoreCase))
+                {
+                    continue;
+                }
+
+                if (block.TryGetProperty("id", out var idEl))
+                {
+                    var toolUseId = idEl.GetString();
+                    if (!string.IsNullOrWhiteSpace(toolUseId))
+                        yield return toolUseId!;
+                }
+            }
+        }
+        finally
+        {
+            doc?.Dispose();
+        }
+    }
+}

src/AxCopilot/Services/Agent/AgentQueryContextBuilder.cs

@@ -47,7 +47,7 @@ public static class AgentQueryContextBuilder
         }
 
         var startIndex = FindWindowStartIndex(sourceMessages, out var boundaryApplied);
-        var adjustedStartIndex = AdjustStartIndexForToolPairs(sourceMessages, startIndex, out var preservedToolPairs);
+        var adjustedStartIndex = AgentMessageInvariantHelper.AdjustStartIndexForToolPairs(sourceMessages, startIndex, out var preservedToolPairs);
         var toolPairExpanded = adjustedStartIndex < startIndex;
 
         var windowMessages = new List<ChatMessage>(sourceMessages.Count);
@@ -112,120 +112,6 @@ public static class AgentQueryContextBuilder
                || content.StartsWith("[이전 압축 경계 병합", StringComparison.Ordinal);
     }
 
-    private static int AdjustStartIndexForToolPairs(
-        IReadOnlyList<ChatMessage> sourceMessages,
-        int startIndex,
-        out int preservedToolPairs)
-    {
-        preservedToolPairs = 0;
-        if (startIndex <= 0)
-            return startIndex;
-
-        var toolResultIds = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
-        for (var i = startIndex; i < sourceMessages.Count; i++)
-        {
-            if (!TryGetToolResultId(sourceMessages[i], out var toolResultId))
-                continue;
-
-            toolResultIds.Add(toolResultId);
-        }
-
-        if (toolResultIds.Count == 0)
-            return startIndex;
-
-        var toolUseIdsInWindow = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
-        for (var i = startIndex; i < sourceMessages.Count; i++)
-        {
-            foreach (var toolUseId in EnumerateToolUseIds(sourceMessages[i]))
-                toolUseIdsInWindow.Add(toolUseId);
-        }
-
-        toolResultIds.ExceptWith(toolUseIdsInWindow);
-        if (toolResultIds.Count == 0)
-            return startIndex;
-
-        var adjustedStart = startIndex;
-        for (var i = startIndex - 1; i >= 0 && toolResultIds.Count > 0; i--)
-        {
-            var foundAny = false;
-            foreach (var toolUseId in EnumerateToolUseIds(sourceMessages[i]))
-            {
-                if (!toolResultIds.Remove(toolUseId))
-                    continue;
-
-                preservedToolPairs++;
-                foundAny = true;
-            }
-
-            if (foundAny)
-                adjustedStart = i;
-        }
-
-        return adjustedStart;
-    }
-
-    private static bool TryGetToolResultId(ChatMessage message, out string toolResultId)
-    {
-        toolResultId = "";
-        if (!string.Equals(message.Role, "user", StringComparison.OrdinalIgnoreCase))
-            return false;
-
-        var content = message.Content ?? "";
-        if (!content.StartsWith("{\"type\":\"tool_result\"", StringComparison.Ordinal))
-            return false;
-
-        try
-        {
-            using var doc = JsonDocument.Parse(content);
-            toolResultId = doc.RootElement.TryGetProperty("tool_use_id", out var idEl)
-                ? idEl.GetString() ?? ""
-                : "";
-            return !string.IsNullOrWhiteSpace(toolResultId);
-        }
-        catch
-        {
-            return false;
-        }
-    }
-
-    private static IEnumerable<string> EnumerateToolUseIds(ChatMessage message)
-    {
-        if (!string.Equals(message.Role, "assistant", StringComparison.OrdinalIgnoreCase))
-            yield break;
-
-        var content = message.Content ?? "";
-        if (!content.StartsWith("{\"_tool_use_blocks\"", StringComparison.Ordinal))
-            yield break;
-
-        JsonDocument? doc = null;
-        try
-        {
-            doc = JsonDocument.Parse(content);
-            if (!doc.RootElement.TryGetProperty("_tool_use_blocks", out var blocksEl) || blocksEl.ValueKind != JsonValueKind.Array)
-                yield break;
-
-            foreach (var block in blocksEl.EnumerateArray())
-            {
-                if (!block.TryGetProperty("type", out var typeEl)
-                    || !string.Equals(typeEl.GetString(), "tool_use", StringComparison.OrdinalIgnoreCase))
-                {
-                    continue;
-                }
-
-                if (block.TryGetProperty("id", out var idEl))
-                {
-                    var toolUseId = idEl.GetString();
-                    if (!string.IsNullOrWhiteSpace(toolUseId))
-                        yield return toolUseId!;
-                }
-            }
-        }
-        finally
-        {
-            doc?.Dispose();
-        }
-    }
-
     private static int ApplyOldToolResultBudget(List<ChatMessage> messages)
     {
         var nonSystemIndexes = messages
@@ -244,7 +130,7 @@ public static class AgentQueryContextBuilder
         for (var i = 0; i < protectedStart; i++)
         {
             var message = messages[i];
-            if (!TryGetToolResultId(message, out _))
+            if (!AgentMessageInvariantHelper.TryGetToolResultId(message, out _))
                 continue;
 
             var content = message.Content ?? "";

src/AxCopilot/Services/Agent/ContextCondenser.cs

@@ -43,6 +43,14 @@ public static class ContextCondenser
     private const int AutoCompactBufferTokens = 13_000;
     private const int SummaryReserveTokens = 20_000;
 
+    private sealed class CompactionWindow
+    {
+        public ChatMessage? SystemMessage { get; init; }
+        public required List<ChatMessage> OldMessages { get; init; }
+        public required List<ChatMessage> RecentMessages { get; init; }
+        public int PreservedToolPairs { get; init; }
+    }
+
     /// <summary>모델별 입력 토큰 한도 (대략).</summary>
     private static int GetModelInputLimit(string service, string model)
     {
@@ -212,6 +220,26 @@ public static class ContextCondenser
         return result;
     }
 
+    private static CompactionWindow SplitCompactionWindow(List<ChatMessage> messages, int extraTrailingProtection)
+    {
+        var systemMsg = messages.FirstOrDefault(m => m.Role == "system");
+        var nonSystemMessages = messages.Where(m => m.Role != "system").ToList();
+        var trailingCount = Math.Min(RecentKeepCount + Math.Max(0, extraTrailingProtection), nonSystemMessages.Count);
+        var splitStart = Math.Max(0, nonSystemMessages.Count - trailingCount);
+        var adjustedStart = AgentMessageInvariantHelper.AdjustStartIndexForToolPairs(
+            nonSystemMessages,
+            splitStart,
+            out var preservedToolPairs);
+
+        return new CompactionWindow
+        {
+            SystemMessage = systemMsg,
+            OldMessages = nonSystemMessages.Take(adjustedStart).ToList(),
+            RecentMessages = nonSystemMessages.Skip(adjustedStart).ToList(),
+            PreservedToolPairs = preservedToolPairs,
+        };
+    }
+
     /// <summary>
     /// 1단계: 대용량 도구 결과를 축약합니다.
     /// tool_result JSON이나 긴 파일 내용 등을 핵심만 남기고 자릅니다.
@@ -286,13 +314,10 @@ public static class ContextCondenser
     /// </summary>
     private static (int BoundaryCount, int SingleCount) MicrocompactOlderMessages(List<ChatMessage> messages)
     {
-        var systemMsg = messages.FirstOrDefault(m => m.Role == "system");
+        var window = SplitCompactionWindow(messages, extraTrailingProtection: 2);
-        var nonSystemMessages = messages.Where(m => m.Role != "system").ToList();
+        if (window.OldMessages.Count == 0 || window.RecentMessages.Count <= RecentKeepCount) return (0, 0);
-        if (nonSystemMessages.Count <= RecentKeepCount + 2) return (0, 0);
+        var oldMessages = window.OldMessages;
-
+        var recentMessages = window.RecentMessages;
-        var keepCount = Math.Min(RecentKeepCount, nonSystemMessages.Count);
-        var recentMessages = nonSystemMessages.Skip(nonSystemMessages.Count - keepCount).ToList();
-        var oldMessages = nonSystemMessages.Take(nonSystemMessages.Count - keepCount).ToList();
 
         var rewritten = new List<ChatMessage>(oldMessages.Count);
         bool changed = false;
@@ -347,7 +372,7 @@ public static class ContextCondenser
         if (!changed) return (0, 0);
 
         messages.Clear();
-        if (systemMsg != null) messages.Add(systemMsg);
+        if (window.SystemMessage != null) messages.Add(window.SystemMessage);
         messages.AddRange(rewritten);
         messages.AddRange(recentMessages);
         return (boundaryCount, singleCount);
@@ -355,13 +380,10 @@ public static class ContextCondenser
 
     private static int SessionMemoryCompactOlderMessages(List<ChatMessage> messages)
     {
-        var systemMsg = messages.FirstOrDefault(m => m.Role == "system");
+        var window = SplitCompactionWindow(messages, extraTrailingProtection: 3);
-        var nonSystemMessages = messages.Where(m => m.Role != "system").ToList();
+        if (window.OldMessages.Count == 0 || window.RecentMessages.Count <= RecentKeepCount) return 0;
-        if (nonSystemMessages.Count <= RecentKeepCount + 3) return 0;
+        var oldMessages = window.OldMessages;
-
+        var recentMessages = window.RecentMessages;
-        var keepCount = Math.Min(RecentKeepCount, nonSystemMessages.Count);
-        var recentMessages = nonSystemMessages.Skip(nonSystemMessages.Count - keepCount).ToList();
-        var oldMessages = nonSystemMessages.Take(nonSystemMessages.Count - keepCount).ToList();
 
         var candidates = oldMessages
             .Select((message, index) => new { message, index })
@@ -415,7 +437,7 @@ public static class ContextCondenser
         }
 
         messages.Clear();
-        if (systemMsg != null) messages.Add(systemMsg);
+        if (window.SystemMessage != null) messages.Add(window.SystemMessage);
         messages.AddRange(rewritten);
         messages.AddRange(recentMessages);
         return candidates.Count;
@@ -437,13 +459,10 @@ public static class ContextCondenser
 
     private static (int SnippedCount, int CollapsedCount) CollapseAndSnipOlderMessages(List<ChatMessage> messages)
     {
-        var systemMsg = messages.FirstOrDefault(m => m.Role == "system");
+        var window = SplitCompactionWindow(messages, extraTrailingProtection: 2);
-        var nonSystemMessages = messages.Where(m => m.Role != "system").ToList();
+        if (window.OldMessages.Count == 0 || window.RecentMessages.Count <= RecentKeepCount) return (0, 0);
-        if (nonSystemMessages.Count <= RecentKeepCount + 2) return (0, 0);
+        var oldMessages = window.OldMessages;
-
+        var recentMessages = window.RecentMessages;
-        var keepCount = Math.Min(RecentKeepCount, nonSystemMessages.Count);
-        var recentMessages = nonSystemMessages.Skip(nonSystemMessages.Count - keepCount).ToList();
-        var oldMessages = nonSystemMessages.Take(nonSystemMessages.Count - keepCount).ToList();
 
         var rewritten = new List<ChatMessage>(oldMessages.Count);
         int snippedCount = 0;
@@ -494,7 +513,7 @@ public static class ContextCondenser
         if (snippedCount == 0 && collapsedCount == 0) return (0, 0);
 
         messages.Clear();
-        if (systemMsg != null) messages.Add(systemMsg);
+        if (window.SystemMessage != null) messages.Add(window.SystemMessage);
         messages.AddRange(rewritten);
         messages.AddRange(recentMessages);
         return (snippedCount, collapsedCount);
@@ -680,13 +699,10 @@ public static class ContextCondenser
     private static async Task<bool> SummarizeOldMessagesAsync(
         List<ChatMessage> messages, ILlmService llm, CancellationToken ct)
     {
-        var systemMsg = messages.FirstOrDefault(m => m.Role == "system");
+        var window = SplitCompactionWindow(messages, extraTrailingProtection: 0);
-        var systemCount = systemMsg != null ? 1 : 0;
+        var systemMsg = window.SystemMessage;
-        var nonSystemMessages = messages.Where(m => m.Role != "system").ToList();
+        var oldMessages = window.OldMessages;
-
+        var recentMessages = window.RecentMessages;
-        var keepCount = Math.Min(RecentKeepCount, nonSystemMessages.Count);
-        var recentMessages = nonSystemMessages.Skip(nonSystemMessages.Count - keepCount).ToList();
-        var oldMessages = nonSystemMessages.Take(nonSystemMessages.Count - keepCount).ToList();
 
         if (oldMessages.Count < 3) return false;