feat: Introduce robust hashline anchor validation and new editing tools.

Hashline/HashlineValidator.cs

@@ -62,17 +62,14 @@ internal static class HashlineValidator
 
         if (lineNumber < 1 || lineNumber > lines.Length)
         {
-            error = $"Anchor '{anchor}': line {lineNumber} is out of range " +
+            error = $"Anchor '{anchor}': line {lineNumber} is out of range. Re-read the file ({lines.Length} lines).";
-                    $"(file has {lines.Length} line(s)).";
             return false;
         }
 
         string actualHash = HashlineEncoder.ComputeHash(lines[lineNumber - 1].AsSpan(), lineNumber);
         if (!string.Equals(actualHash, expectedHash, StringComparison.OrdinalIgnoreCase))
         {
-            error = $"Anchor '{anchor}': hash mismatch at line {lineNumber} " +
+            error = $"Anchor '{anchor}': hash mismatch at line {lineNumber}. The file has changed — re-read before editing.";
-                    $"(expected '{expectedHash}', got '{actualHash}'). " +
-                    $"The file has changed — re-read before editing.";
             return false;
         }
 
@@ -98,10 +95,7 @@ internal static class HashlineValidator
         out int endIndex,
         out string error)
     {
-        startIndex = -1;
         endIndex = -1;
-        error = string.Empty;
-
         if (!TryResolve(startAnchor, lines, out startIndex, out error))
             return false;
 
@@ -110,8 +104,7 @@ internal static class HashlineValidator
 
         if (startIndex > endIndex)
         {
-            error = $"Range error: start anchor '{startAnchor}' (line {startIndex + 1}) " +
+            error = $"Range error: start anchor is after end anchor.";
-                    $"is after end anchor '{endAnchor}' (line {endIndex + 1}).";
             return false;
         }
 

ReplLoop.cs

@@ -216,20 +216,48 @@ internal sealed class ReplLoop
                     }
                     AnsiConsole.WriteLine();
                 }
-            }
-            catch (OperationCanceledException)
-            {
-                AnsiConsole.WriteLine();
-                AnsiConsole.MarkupLine("[dim grey]  ✗ Cancelled[/]");
-                AnsiConsole.Write(new Rule().RuleStyle(Style.Parse("grey dim")));
-                AnsiConsole.WriteLine();
 
-                if (!string.IsNullOrEmpty(fullResponse))
+                // Save session after each LLM turn completes
+                try
                 {
-                    _session.History.Add(new ChatMessage(ChatRole.Assistant, fullResponse));
+                    const string sessionPath = ".anchor/session.json";
+                    var directory = Path.GetDirectoryName(sessionPath);
+                    if (!string.IsNullOrEmpty(directory) && !Directory.Exists(directory))
+                    {
+                        Directory.CreateDirectory(directory);
+                    }
+                    await _session.SaveAsync(sessionPath, default);
+                }
+                catch (OperationCanceledException)
+                {
+                    AnsiConsole.WriteLine();
+                    AnsiConsole.MarkupLine("[dim grey]  ✗ Cancelled[/]");
+                    AnsiConsole.Write(new Rule().RuleStyle(Style.Parse("grey dim")));
+                    AnsiConsole.WriteLine();
+
+                    if (!string.IsNullOrEmpty(fullResponse))
+                    {
+                        _session.History.Add(new ChatMessage(ChatRole.Assistant, fullResponse));
+                    }
+                    _session.History.Add(new ChatMessage(ChatRole.User,
+                        "[Response cancelled by user. Acknowledge briefly and wait for the next instruction. Do not repeat what was already said.]"));
+                }
+                catch (Exception ex)
+                {
+                    AnsiConsole.WriteLine();
+                    AnsiConsole.Write(
+                        new Panel($"[red]{Markup.Escape(ex.Message)}[/]")
+                            .Header("[bold red] Error [/]")
+                            .BorderColor(Color.Red)
+                            .RoundedBorder()
+                            .Padding(1, 0));
+                    AnsiConsole.WriteLine();
+                }
+                finally
+                {
+                    responseCts?.Dispose();
+                    responseCts = null;
                 }
-                _session.History.Add(new ChatMessage(ChatRole.User,
-                    "[Response cancelled by user. Acknowledge briefly and wait for the next instruction. Do not repeat what was already said.]"));
             }
             catch (Exception ex)
             {
@@ -242,11 +270,6 @@ internal sealed class ReplLoop
                         .Padding(1, 0));
                 AnsiConsole.WriteLine();
             }
-            finally
-            {
-                responseCts?.Dispose();
-                responseCts = null;
-            }
         }
     }
 }

Tools/EditTools.cs

@@ -66,7 +66,7 @@ internal static partial class EditTools
         Log($"  Replacing {endAnchor.Split(':')[0]}-{startAnchor.Split(':')[0]} lines with {newLines.Length} new lines");
 
         if (!File.Exists(path))
-            return $"ERROR: File not found: {path}";
+            return $"ERROR: File not found: {path}\n Check the correct path and try again.";
 
         try
         {
@@ -74,7 +74,7 @@ internal static partial class EditTools
 
             if (!HashlineValidator.TryResolveRange(startAnchor, endAnchor, lines,
                     out int startIdx, out int endIdx, out string error))
-                return $"ERROR: {error}";
+                return $"ERROR: Anchor validation failed\n{error}";
 
             var result = new List<string>(lines.Length - (endIdx - startIdx + 1) + newLines.Length);
             result.AddRange(lines[..startIdx]);
@@ -86,7 +86,7 @@ internal static partial class EditTools
         }
         catch (Exception ex)
         {
-            return $"ERROR modifying '{path}': {ex.Message}";
+            return $"ERROR modifying '{path}': {ex.Message}.\nThis is a bug. Tell the user about it.";
         }
     }
 
@@ -120,22 +120,22 @@ internal static partial class EditTools
         }
         catch (Exception ex)
         {
-            return $"ERROR modifying '{path}': {ex.Message}";
+            return $"ERROR modifying '{path}': {ex.Message}\nThis is a bug. Tell the user about it.";
         }
     }
 
 
 
-    [Description("Delete a file or directory. Use mode='file' to delete a file, mode='dir' to delete a directory.")] 
+    [Description("Delete a file or directory. Use mode='file' to delete a file, mode='dir' to delete a directory.")]
     public static string Delete(
         [Description("Path to the file or directory to delete.")] string path,
         [Description("Type of deletion: 'file' or 'dir'. Defaults to 'file'.")] string mode = "file")
     {
         path = FileTools.ResolvePath(path);
-        string targetType = mode.ToLower() == "dir" ? "directory" : "file";
+        string targetType = mode.Equals("dir", StringComparison.CurrentCultureIgnoreCase) ? "directory" : "file";
         Log($"Deleting {targetType}: {path}");
 
-        if (mode.ToLower() == "dir")
+        if (mode.Equals("dir", StringComparison.CurrentCultureIgnoreCase))
         {
             if (!Directory.Exists(path))
                 return $"ERROR: Directory not found: {path}";
@@ -147,7 +147,7 @@ internal static partial class EditTools
             }
             catch (Exception ex)
             {
-                return $"ERROR deleting directory '{path}': {ex.Message}";
+                return $"ERROR deleting directory '{path}': {ex.Message}\nThis is a bug. Tell the user about it.";
             }
         }
         else
@@ -162,12 +162,12 @@ internal static partial class EditTools
             }
             catch (Exception ex)
             {
-                return $"ERROR deleting '{path}': {ex.Message}";
+                return $"ERROR deleting '{path}': {ex.Message}\nThis is a bug. Tell the user about it.";
             }
         }
     }
 
-    [Description("Move or copy a file to a new location.")] 
+    [Description("Move or copy a file to a new location.")]
     public static string MoveFile(
         [Description("Current path to the file.")] string sourcePath,
         [Description("New path for the file.")] string destinationPath,
@@ -198,7 +198,7 @@ internal static partial class EditTools
         }
         catch (Exception ex)
         {
-            return $"ERROR {action.ToLower()} file: {ex.Message}";
+            return $"ERROR {action.ToLower()} file: {ex.Message}\nThis is a bug. Tell the user about it.";
         }
     }
 
@@ -241,7 +241,7 @@ internal static partial class EditTools
                         File.WriteAllText(path, "");
                         Log($"  (created new file)");
                     }
-                    
+
                     using (var writer = new System.IO.StreamWriter(path, true))
                     {
                         foreach (var line in content)
@@ -279,7 +279,7 @@ internal static partial class EditTools
         }
         catch (Exception ex)
         {
-            return $"ERROR writing to '{path}': {ex.Message}";
+            return $"ERROR writing to '{path}': {ex.Message}\nThis is a bug. Tell the user about it.";
         }
     }