Widthdom · Widthdom · Apr 24, 2026 · Apr 23, 2026 · Apr 23, 2026 · Apr 23, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
diff --git a/FolderDiffIL4DotNet.Tests/ProgramRunnerTests.HelpVersion.cs b/FolderDiffIL4DotNet.Tests/ProgramRunnerTests.HelpVersion.cs
@@ -586,11 +586,17 @@ public async Task RunAsync_OpenReportsFlag_WhenOutputTargetsExistingFile_Returns
                 Assert.Equal(4, exitCode);
                 string errorOutput = errorWriter.ToString();
                 Assert.Contains("Failed to open folder", errorOutput, StringComparison.Ordinal);
+                Assert.Contains("during stage 'validating target path'", errorOutput, StringComparison.Ordinal);
                 Assert.Contains(outputFile, errorOutput, StringComparison.Ordinal);
                 Assert.Contains("IOException", errorOutput, StringComparison.Ordinal);
+                Assert.Contains("TargetPathIsPathRooted=True", errorOutput, StringComparison.Ordinal);
+                Assert.Contains("TargetPathLooksPathLike=True", errorOutput, StringComparison.Ordinal);
                 Assert.Empty(startedProcesses);
                 var loggedMessage = Assert.Single(logger.Messages);
                 Assert.Contains("Failed to open folder", loggedMessage, StringComparison.Ordinal);
+                Assert.Contains("during stage 'validating target path'", loggedMessage, StringComparison.Ordinal);
+                Assert.Contains("TargetPathIsPathRooted=True", loggedMessage, StringComparison.Ordinal);
+                Assert.Contains("TargetPathLooksPathLike=True", loggedMessage, StringComparison.Ordinal);
             }
             finally
             {
@@ -635,10 +641,12 @@ public async Task RunAsync_OpenReportsFlag_WhenFolderLauncherThrows_ReturnsExecu
 
                 string errorOutput = errorWriter.ToString();
                 Assert.Contains("Failed to open folder", errorOutput, StringComparison.Ordinal);
+                Assert.Contains("during stage 'launching file manager'", errorOutput, StringComparison.Ordinal);
                 Assert.Contains(Path.GetFullPath(tempDir), errorOutput, StringComparison.Ordinal);
                 Assert.Contains("InvalidOperationException", errorOutput, StringComparison.Ordinal);
                 var loggedMessage = Assert.Single(logger.Messages);
                 Assert.Contains("Failed to open folder", loggedMessage, StringComparison.Ordinal);
+                Assert.Contains("during stage 'launching file manager'", loggedMessage, StringComparison.Ordinal);
             }
             finally
             {
@@ -853,8 +861,12 @@ public async Task RunAsync_MultipleOpenFolderFlags_WhenSecondLauncherFails_DoesN
                 Assert.Contains("Failed to open folder", errorOutput, StringComparison.Ordinal);
                 Assert.Contains(Path.GetFullPath(tempDir), errorOutput, StringComparison.Ordinal);
                 Assert.Contains("InvalidOperationException", errorOutput, StringComparison.Ordinal);
+                Assert.Contains("TargetPathIsPathRooted=True", errorOutput, StringComparison.Ordinal);
+                Assert.Contains("TargetPathLooksPathLike=True", errorOutput, StringComparison.Ordinal);
                 var loggedMessage = Assert.Single(logger.Messages);
                 Assert.Contains("Failed to open folder", loggedMessage, StringComparison.Ordinal);
+                Assert.Contains("TargetPathIsPathRooted=True", loggedMessage, StringComparison.Ordinal);
+                Assert.Contains("TargetPathLooksPathLike=True", loggedMessage, StringComparison.Ordinal);
             }
             finally
             {
@@ -998,7 +1010,10 @@ public async Task RunAsync_OpenReportsFlag_WhenLoggerInitializationFails_WithJso
                 Assert.Contains("UnauthorizedAccessException", root.GetProperty("message").GetString(), StringComparison.Ordinal);
                 Assert.Contains(typeof(UnauthorizedAccessException).FullName, root.GetProperty("exceptionType").GetString(), StringComparison.Ordinal);
                 Assert.Contains("Failed to open folder", errorLines[1], StringComparison.Ordinal);
+                Assert.Contains("during stage 'launching file manager'", errorLines[1], StringComparison.Ordinal);
                 Assert.Contains(Path.GetFullPath(appDataScope.ReportsRootAbsolutePath), errorLines[1], StringComparison.Ordinal);
+                Assert.Contains("TargetPathIsPathRooted=True", errorLines[1], StringComparison.Ordinal);
+                Assert.Contains("TargetPathLooksPathLike=True", errorLines[1], StringComparison.Ordinal);
             }
             finally
             {
@@ -1136,10 +1151,16 @@ public async Task RunAsync_MultipleOpenFolderFlags_WhenFirstLauncherFails_DoesNo
 
                 string errorOutput = errorWriter.ToString();
                 Assert.Contains("Failed to open folder", errorOutput, StringComparison.Ordinal);
+                Assert.Contains("during stage 'launching file manager'", errorOutput, StringComparison.Ordinal);
                 Assert.Contains(Path.GetFullPath(tempDir), errorOutput, StringComparison.Ordinal);
                 Assert.Contains("InvalidOperationException", errorOutput, StringComparison.Ordinal);
+                Assert.Contains("TargetPathIsPathRooted=True", errorOutput, StringComparison.Ordinal);
+                Assert.Contains("TargetPathLooksPathLike=True", errorOutput, StringComparison.Ordinal);
                 var loggedMessage = Assert.Single(logger.Messages);
                 Assert.Contains("Failed to open folder", loggedMessage, StringComparison.Ordinal);
+                Assert.Contains("during stage 'launching file manager'", loggedMessage, StringComparison.Ordinal);
+                Assert.Contains("TargetPathIsPathRooted=True", loggedMessage, StringComparison.Ordinal);
+                Assert.Contains("TargetPathLooksPathLike=True", loggedMessage, StringComparison.Ordinal);
             }
             finally
             {

diff --git a/FolderDiffIL4DotNet.Tests/Runner/DiffPipelineExecutorTests.cs b/FolderDiffIL4DotNet.Tests/Runner/DiffPipelineExecutorTests.cs
@@ -146,6 +146,11 @@ public async Task ExecuteAsync_WhenPostProcessActionThrows_LogsActionAndExceptio
             Assert.Contains(nameof(ThrowingPostProcessAction), warning.Message, StringComparison.Ordinal);
             Assert.Contains("position 1/1", warning.Message, StringComparison.Ordinal);
             Assert.Contains("Order=0", warning.Message, StringComparison.Ordinal);
+            Assert.Contains($"ReportsFolder='{reportDir}'", warning.Message, StringComparison.Ordinal);
+            Assert.Contains("Added=0", warning.Message, StringComparison.Ordinal);
+            Assert.Contains("Removed=0", warning.Message, StringComparison.Ordinal);
+            Assert.Contains("Modified=0", warning.Message, StringComparison.Ordinal);
+            Assert.Contains("Unchanged=0", warning.Message, StringComparison.Ordinal);
             Assert.Contains(nameof(InvalidOperationException), warning.Message, StringComparison.Ordinal);
             Assert.NotNull(warning.Exception);
         }

diff --git a/FolderDiffIL4DotNet.Tests/Runner/PluginLoaderTests.cs b/FolderDiffIL4DotNet.Tests/Runner/PluginLoaderTests.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Reflection;
 using System.Security.Cryptography;
 using FolderDiffIL4DotNet.Runner;
 using FolderDiffIL4DotNet.Tests.Helpers;
@@ -64,6 +65,27 @@ public void LoadPlugins_EmptySearchPath_ReturnsEmptyList()
             Assert.Empty(result);
         }
 
+        [Fact]
+        public void TryEnumeratePluginDirectories_InvalidSearchPath_LogsPathShapeDiagnosticsAndReturnsEmpty()
+        {
+            // Arrange / 準備
+            var method = typeof(PluginLoader).GetMethod("TryEnumeratePluginDirectories", BindingFlags.Instance | BindingFlags.NonPublic);
+            Assert.NotNull(method);
+
+            // Act / 実行
+            var result = method!.Invoke(_loader, new object[] { "bad\0plugin-search-path" });
+
+            // Assert / 検証
+            var directories = Assert.IsAssignableFrom<IEnumerable<string>>(result);
+            Assert.Empty(directories);
+
+            var entry = Assert.Single(_logger.Entries, e => e.Message.Contains("Failed to enumerate plugin search path", StringComparison.Ordinal));
+            Assert.NotNull(entry.Exception);
+            Assert.Contains("PluginSearchPathIsPathRooted=", entry.Message, StringComparison.Ordinal);
+            Assert.Contains("PluginSearchPathLooksPathLike=", entry.Message, StringComparison.Ordinal);
+            Assert.Contains(entry.Exception!.GetType().Name, entry.Message, StringComparison.Ordinal);
+        }
+
         [Fact]
         public void LoadPlugins_SubdirectoryWithoutMatchingDll_ReturnsEmptyList()
         {
@@ -102,6 +124,8 @@ public void LoadPlugins_InvalidDll_LogsWarningWithExceptionTypeAndReturnsEmptyLi
             Assert.Empty(result);
             var entry = Assert.Single(_logger.Entries, e => e.Message.Contains("Failed to load plugin", StringComparison.Ordinal));
             Assert.NotNull(entry.Exception);
+            Assert.Contains("PluginDllPathIsPathRooted=True", entry.Message, StringComparison.Ordinal);
+            Assert.Contains("PluginDllPathLooksPathLike=True", entry.Message, StringComparison.Ordinal);
             Assert.Contains(entry.Exception!.GetType().Name, entry.Message, StringComparison.Ordinal);
         }
 

diff --git a/FolderDiffIL4DotNet.Tests/Services/Caching/ILDiskCacheTests.cs b/FolderDiffIL4DotNet.Tests/Services/Caching/ILDiskCacheTests.cs
@@ -164,6 +164,8 @@ public void Remove_WhenCacheDirectoryBecomesInvalid_LogsCacheDirectoryAndKeyLeng
             Assert.Null(exception);
             var warning = Assert.Single(logger.Entries, entry => entry.LogLevel == AppLogLevel.Warning);
             Assert.Contains("Failed to remove disk cache file", warning.Message, StringComparison.Ordinal);
+            Assert.Contains("during explicit remove", warning.Message, StringComparison.Ordinal);
+            Assert.DoesNotContain("during LRU eviction", warning.Message, StringComparison.Ordinal);
             Assert.Contains(invalidCacheDir, warning.Message, StringComparison.Ordinal);
             Assert.Contains("CacheDirectoryIsPathRooted=True", warning.Message, StringComparison.Ordinal);
             Assert.Contains("CacheDirectoryLooksPathLike=True", warning.Message, StringComparison.Ordinal);

diff --git a/FolderDiffIL4DotNet.Tests/Services/FileDiffServiceUnitTests.Hooks.cs b/FolderDiffIL4DotNet.Tests/Services/FileDiffServiceUnitTests.Hooks.cs
@@ -127,6 +127,8 @@ public async Task FilesAreEqualAsync_BeforeCompareHookThrows_LogsAndProceedsToBu
             Assert.Contains(logger.Messages,
                 m => m.Contains("Plugin BeforeCompare hook 'FakeFileComparisonHook' failed", StringComparison.Ordinal)
                     && m.Contains("Order=0", StringComparison.Ordinal)
+                    && m.Contains("OldRoot='/virtual/old'", StringComparison.Ordinal)
+                    && m.Contains("NewRoot='/virtual/new'", StringComparison.Ordinal)
                     && m.Contains("InvalidOperationException", StringComparison.Ordinal));
         }
 
@@ -155,6 +157,8 @@ public async Task FilesAreEqualAsync_AfterCompareHookThrows_LogsButDoesNotAffect
             Assert.Contains(logger.Messages,
                 m => m.Contains("Plugin AfterCompare hook 'FakeFileComparisonHook' failed", StringComparison.Ordinal)
                     && m.Contains("Order=0", StringComparison.Ordinal)
+                    && m.Contains("OldRoot='/virtual/old'", StringComparison.Ordinal)
+                    && m.Contains("NewRoot='/virtual/new'", StringComparison.Ordinal)
                     && m.Contains("InvalidOperationException", StringComparison.Ordinal));
         }
 

diff --git a/FolderDiffIL4DotNet.Tests/Services/FolderDiffServiceUnitTests.cs b/FolderDiffIL4DotNet.Tests/Services/FolderDiffServiceUnitTests.cs
@@ -451,6 +451,10 @@ public async Task ExecuteFolderDiffAsync_WhenCreatingIlOutputDirectoryThrowsDire
                 entry => entry.LogLevel == AppLogLevel.Error
                     && entry.Exception is DirectoryNotFoundException
                     && entry.Message.Contains($"An error occurred while diffing '{oldDir}' and '{newDir}' during phase 'creating IL output directories'.", StringComparison.Ordinal)
+                    && entry.Message.Contains("OldFolderIsPathRooted=True", StringComparison.Ordinal)
+                    && entry.Message.Contains("OldFolderLooksPathLike=True", StringComparison.Ordinal)
+                    && entry.Message.Contains("NewFolderIsPathRooted=True", StringComparison.Ordinal)
+                    && entry.Message.Contains("NewFolderLooksPathLike=True", StringComparison.Ordinal)
                     && entry.Message.Contains("Failure=DirectoryNotFoundException: parent directory missing", StringComparison.Ordinal));
         }
 
@@ -489,6 +493,10 @@ public async Task ExecuteFolderDiffAsync_WhenFileDiffThrowsUnexpectedException_L
                 entry => entry.LogLevel == AppLogLevel.Error
                     && entry.Exception is FormatException
                     && entry.Message.Contains($"An unexpected error occurred while diffing '{oldDir}' and '{newDir}' during phase 'classifying files sequentially'.", StringComparison.Ordinal)
+                    && entry.Message.Contains("OldFolderIsPathRooted=True", StringComparison.Ordinal)
+                    && entry.Message.Contains("OldFolderLooksPathLike=True", StringComparison.Ordinal)
+                    && entry.Message.Contains("NewFolderIsPathRooted=True", StringComparison.Ordinal)
+                    && entry.Message.Contains("NewFolderLooksPathLike=True", StringComparison.Ordinal)
                     && entry.Message.Contains("Failure=FormatException: unexpected compare failure", StringComparison.Ordinal));
         }
 

diff --git a/FolderDiffIL4DotNet.Tests/Services/ReviewChecklistLoaderTests.cs b/FolderDiffIL4DotNet.Tests/Services/ReviewChecklistLoaderTests.cs
@@ -32,6 +32,7 @@ public void Load_WhenChecklistPathResolutionFails_LogsWarningWithExceptionTypeAn
                     && entry.Message.Contains("Review checklist path could not be resolved", StringComparison.Ordinal));
             Assert.Contains(AppDataPaths.LOCAL_APP_DATA_OVERRIDE_KEY, warning.Message, StringComparison.Ordinal);
             Assert.Contains("OverridePresent=True", warning.Message, StringComparison.Ordinal);
+            Assert.Contains("OverrideValueType=String", warning.Message, StringComparison.Ordinal);
             Assert.Contains(nameof(InvalidOperationException), warning.Message, StringComparison.Ordinal);
             Assert.True(warning.ShouldOutputMessageToConsole);
         }
@@ -55,6 +56,7 @@ public void Load_WhenChecklistPathOverrideIsMalformed_LogsWarningAndReturnsEmpty
                         && entry.Message.Contains("Review checklist path could not be resolved", StringComparison.Ordinal));
                 Assert.Contains(AppDataPaths.LOCAL_APP_DATA_OVERRIDE_KEY, warning.Message, StringComparison.Ordinal);
                 Assert.Contains("OverridePresent=True", warning.Message, StringComparison.Ordinal);
+                Assert.Contains("OverrideValueType=String", warning.Message, StringComparison.Ordinal);
                 Assert.Contains(nameof(ArgumentException), warning.Message, StringComparison.Ordinal);
                 Assert.True(warning.ShouldOutputMessageToConsole);
             }
@@ -93,5 +95,30 @@ public void Load_WhenChecklistPathIsUnreadable_LogsWarningWithConsistentExceptio
                 || warning.Message.Contains($", {nameof(IOException)}):", StringComparison.Ordinal));
             Assert.True(warning.ShouldOutputMessageToConsole);
         }
+
+        [Fact]
+        [Trait("Category", "Unit")]
+        public void Load_WhenChecklistJsonIsInvalid_LogsJsonCoordinatesAndReturnsEmpty()
+        {
+            using var appDataScope = new AppDataOverrideScope(
+                Path.Combine(Path.GetTempPath(), "fd-review-checklist-loader-" + Guid.NewGuid().ToString("N")));
+            var checklistPath = AppDataPaths.GetDefaultReviewChecklistFileAbsolutePath();
+            Directory.CreateDirectory(Path.GetDirectoryName(checklistPath)!);
+            File.WriteAllText(checklistPath, "{\n  invalid-json\n}", System.Text.Encoding.UTF8);
+
+            var logger = new TestLogger();
+
+            var items = ReviewChecklistLoader.Load(logger);
+
+            Assert.Empty(items);
+            var warning = Assert.Single(
+                logger.Entries,
+                entry => entry.LogLevel == AppLogLevel.Warning
+                    && entry.Message.Contains("invalid JSON", StringComparison.Ordinal));
+            Assert.Contains("LineNumber=", warning.Message, StringComparison.Ordinal);
+            Assert.Contains("BytePositionInLine=", warning.Message, StringComparison.Ordinal);
+            Assert.Contains(nameof(System.Text.Json.JsonException), warning.Message, StringComparison.Ordinal);
+            Assert.True(warning.ShouldOutputMessageToConsole);
+        }
     }
 }
diff --git a/Runner/DiffPipelineExecutor.cs b/Runner/DiffPipelineExecutor.cs
@@ -225,7 +225,7 @@ private async Task RunPostProcessActionsAsync(
                 catch (Exception ex)
                 {
                     _logger.LogMessage(AppLogLevel.Warning,
-                        $"Post-process action '{action.GetType().Name}' failed at position {actionIndex + 1}/{actions.Count} (Order={action.Order}, {ex.GetType().Name}): {ex.Message}",
+                        $"Post-process action '{action.GetType().Name}' failed at position {actionIndex + 1}/{actions.Count} (Order={action.Order}, ReportsFolder='{context.ReportsFolderAbsolutePath}', Added={context.AddedCount}, Removed={context.RemovedCount}, Modified={context.ModifiedCount}, Unchanged={context.UnchangedCount}, {ex.GetType().Name}): {ex.Message}",
                         shouldOutputMessageToConsole: true, ex);
                 }
 #pragma warning restore CA1031

diff --git a/Runner/PluginLoader.cs b/Runner/PluginLoader.cs
@@ -4,6 +4,7 @@
 using System.Linq;
 using System.Reflection;
 using System.Security.Cryptography;
+using FolderDiffIL4DotNet.Common;
 using FolderDiffIL4DotNet.Plugin.Abstractions;
 using FolderDiffIL4DotNet.Services;
 
@@ -96,7 +97,7 @@ private IEnumerable<string> TryEnumeratePluginDirectories(string searchPath)
                 or UnauthorizedAccessException or ArgumentException or NotSupportedException)
             {
                 _logger.LogMessage(AppLogLevel.Warning,
-                    $"Failed to enumerate plugin search path '{searchPath}' ({ex.GetType().Name}): {ex.Message}",
+                    $"Failed to enumerate plugin search path '{searchPath}' ({PathShapeDiagnostics.DescribeState("PluginSearchPath", searchPath)}, {ex.GetType().Name}): {ex.Message}",
                     shouldOutputMessageToConsole: true, ex);
                 return Array.Empty<string>();
             }
@@ -177,7 +178,7 @@ private IEnumerable<string> TryEnumeratePluginDirectories(string searchPath)
             catch (Exception ex)
             {
                 _logger.LogMessage(AppLogLevel.Warning,
-                    $"Failed to load plugin from '{pluginDllPath}': {ex.GetType().Name}: {ex.Message}",
+                    $"Failed to load plugin from '{pluginDllPath}' ({PathShapeDiagnostics.DescribeState("PluginDllPath", pluginDllPath)}, {ex.GetType().Name}): {ex.Message}",
                     shouldOutputMessageToConsole: true, ex);
                 return null;
             }