feat(prompt): focused custom prompt for improvement children so they stay narrow

src/ClaudeDo.Data/PromptFiles.cs

@@ -2,7 +2,7 @@ using System.Text;
 
 namespace ClaudeDo.Data;
 
-public enum PromptKind { System, Planning, PlanningInitial, Retry, DailyPrep, WeeklyReport }
+public enum PromptKind { System, Planning, PlanningInitial, Retry, DailyPrep, WeeklyReport, ImprovementChild }
 
 public static class PromptFiles
 {
@@ -16,6 +16,7 @@ public static class PromptFiles
         PromptKind.Retry => Path.Combine(Root, "retry.md"),
         PromptKind.DailyPrep => Path.Combine(Root, "daily-prep.md"),
         PromptKind.WeeklyReport => Path.Combine(Root, "weekly-report.md"),
+        PromptKind.ImprovementChild => Path.Combine(Root, "improvement-child.md"),
         _ => throw new ArgumentOutOfRangeException(nameof(kind))
     };
 
@@ -59,6 +60,7 @@ public static class PromptFiles
         PromptKind.Retry => RetryDefault,
         PromptKind.DailyPrep => DailyPrepDefault,
         PromptKind.WeeklyReport => WeeklyReportDefault,
+        PromptKind.ImprovementChild => ImprovementChildDefault,
         _ => ""
     };
 
@@ -114,6 +116,21 @@ public static class PromptFiles
         blockers, not for routine decisions you can make yourself.
         """;
 
+    private const string ImprovementChildDefault = """
+        # Out-of-scope follow-up
+
+        You are an improvement follow-up that another task filed via SuggestImprovement.
+        It was deliberately scoped narrow. Do EXACTLY what this task's title and
+        description ask — nothing more.
+
+        - Make the smallest change that satisfies the task. No opportunistic refactors,
+          renames, reformatting, or "while I'm here" cleanup beyond what is asked.
+        - Touch as few files as possible. Do not restructure unrelated code.
+        - Do NOT file further improvements — improvements are one layer deep.
+        - Verify the build and relevant tests before finishing, and report what you ran.
+        - Make one focused commit using the repository's commit-message convention.
+        """;
+
     private const string PlanningSystemDefault = """
         You are the planning assistant for ClaudeDo. Your job is to break a task into
         smaller, independently executable subtasks — the session ends by creating those

src/ClaudeDo.Worker/Runner/TaskRunner.cs

@@ -459,8 +459,13 @@ public sealed class TaskRunner
 
         var systemFile = PromptFiles.ReadOrDefault(PromptKind.System);
 
+        // Improvement children (filed via SuggestImprovement; CreatedBy == ParentTaskId) get a
+        // narrow follow-up prompt so they stay tightly scoped instead of doing "too much".
+        var isImprovementChild = task.ParentTaskId is not null && task.CreatedBy == task.ParentTaskId;
+        var improvementPrompt = isImprovementChild ? PromptFiles.ReadOrDefault(PromptKind.ImprovementChild) : null;
+
         var instructions = MergeInstructions(
-            systemFile, global.DefaultClaudeInstructions, listConfig?.SystemPrompt, task.SystemPrompt);
+            systemFile, improvementPrompt, global.DefaultClaudeInstructions, listConfig?.SystemPrompt, task.SystemPrompt);
 
         return new ClaudeRunConfig(
             Model: task.Model ?? listConfig?.Model ?? global.DefaultModel,

tests/ClaudeDo.Data.Tests/SystemPromptTests.cs

@@ -12,4 +12,13 @@ public class SystemPromptTests
         Assert.Contains("Out-of-scope improvements", prompt);
         Assert.Contains("SuggestImprovement", prompt);
     }
+
+    [Fact]
+    public void ImprovementChildDefault_is_present_and_scopes_narrow()
+    {
+        var prompt = PromptFiles.DefaultFor(PromptKind.ImprovementChild);
+        Assert.False(string.IsNullOrWhiteSpace(prompt));
+        Assert.Contains("follow-up", prompt, StringComparison.OrdinalIgnoreCase);
+        Assert.Contains("nothing more", prompt, StringComparison.OrdinalIgnoreCase);
+    }
 }