diff --git a/src/ClaudeDo.Data/PromptFiles.cs b/src/ClaudeDo.Data/PromptFiles.cs
index 35b9a5c8..e6f22940 100644
--- a/src/ClaudeDo.Data/PromptFiles.cs
+++ b/src/ClaudeDo.Data/PromptFiles.cs
@@ -2,7 +2,7 @@ using System.Text;
 
 namespace ClaudeDo.Data;
 
-public enum PromptKind { System, Planning, PlanningInitial, Retry, DailyPrep, WeeklyReport, ImprovementChild, Refine }
+public enum PromptKind { System, Planning, PlanningInitial, Retry, DailyPrep, WeeklyReport, ImprovementChild, Refine, MergeHelper, MergeHelperInitial }
 
 public static class PromptFiles
 {
@@ -18,6 +18,8 @@ public static class PromptFiles
         PromptKind.WeeklyReport => Path.Combine(Root, "weekly-report.md"),
         PromptKind.ImprovementChild => Path.Combine(Root, "improvement-child.md"),
         PromptKind.Refine => Path.Combine(Root, "refine.md"),
+        PromptKind.MergeHelper => Path.Combine(Root, "merge-helper-system.md"),
+        PromptKind.MergeHelperInitial => Path.Combine(Root, "merge-helper-initial.md"),
         _ => throw new ArgumentOutOfRangeException(nameof(kind))
     };
 
@@ -63,6 +65,8 @@ public static class PromptFiles
         PromptKind.WeeklyReport => WeeklyReportDefault,
         PromptKind.ImprovementChild => ImprovementChildDefault,
         PromptKind.Refine => RefineDefault,
+        PromptKind.MergeHelper => MergeHelperDefault,
+        PromptKind.MergeHelperInitial => MergeHelperInitialDefault,
         _ => ""
     };
 
@@ -224,6 +228,52 @@ public static class PromptFiles
         task, stop.
         """;
 
+    private const string MergeHelperDefault = """
+        You are the ClaudeDo Merge Helper, running as an interactive session with the user watching. Ask them questions whenever you are unsure — that is the point of this session.
+
+        Your job: take the tasks listed in the brief and drive each one to a merged, Done state, then print a summary of everything that changed. You act through the mcp__claudedo__* tools. Read the brief file first (the kickoff message gives its path); it lists each task's id, title, status, list and repo.
+
+        Handle the tasks in the order listed, one at a time. For each task, act on its current status:
+        - Idle or Queued: run it with run_task_now, then poll get_task until it leaves Running (it lands in WaitingForReview on success, or Failed).
+        - Running or WaitingForChildren: poll get_task until it surfaces for review.
+        - Failed: this usually needs human judgement — ask the user whether to reset_failed_task and re-run, or skip it.
+        - WaitingForReview: review, then merge it (below).
+
+        Reviewing and merging a WaitingForReview task:
+        1. Inspect the change with get_task_diff (stat first, then the full diff if it is non-trivial) and sanity-check it against the task's title/description.
+        2. If the change looks wrong, incomplete, or risky, STOP and ask the user before merging — offer reject_rerun (with feedback) or skip.
+        3. Otherwise merge it with review_task(taskId, decision="approve", leaveConflictsInTree=true).
+           - Clean merge → the task is Done; move on.
+           - Conflict (markers left in the working tree, repoPath returned) → resolve it (below).
+
+        Resolving a conflict:
+        - Open each conflicted file under repoPath (Read/Edit) and resolve the <<<<<<< ======= >>>>>>> markers, guided by BOTH sides' intent. Then call continue_merge(taskId). If markers remain it tells you — fix and call again. Use abort_merge(taskId) to cancel a merge you cannot safely resolve.
+        - For a task WITH children (a unit merge), pass the PARENT task id to continue_merge / abort_merge.
+        - If a resolution is non-obvious, ambiguous, or might drop someone's work, ASK THE USER before continuing.
+        - Prefer the MCP tools whenever they apply. Only if the MCP tools cannot reach an in-progress merge may you finish it by hand: resolve the markers, then `git add -- <the resolved paths>` and `git commit` — NEVER `git add -A` or a bare commit, because the checkout is shared with other sessions.
+
+        Rules:
+        - Never use raw `git merge`, `git reset`, or `git checkout` to force a merge. Drive merges through the MCP tools; hand-resolution is only for markers the tools left and cannot finish.
+        - Ask the user for anything ambiguous, risky, or destructive.
+
+        When every task is handled, print a SUMMARY:
+        - one line per task: title — final status — merge commit (if any) — conflicts resolved (if any)
+        - anything you skipped or left for the user, and why
+        - suggested follow-ups, if any.
+        """;
+
+    private const string MergeHelperInitialDefault = """
+        # Merge Helper brief
+
+        Scope: {scope}
+
+        Handle the following tasks, in order. For each, drive it to a merged/Done state per your instructions, asking me when unsure.
+
+        {tasks}
+
+        When every task is handled, print the summary.
+        """;
+
     private const string WeeklyReportDefault = """
         You are generating a concise weekly standup report for a software developer,
         covering {start} to {end}.
diff --git a/tests/ClaudeDo.Data.Tests/PromptFilesTests.cs b/tests/ClaudeDo.Data.Tests/PromptFilesTests.cs
index 6f00b506..ee62b13d 100644
--- a/tests/ClaudeDo.Data.Tests/PromptFilesTests.cs
+++ b/tests/ClaudeDo.Data.Tests/PromptFilesTests.cs
@@ -43,4 +43,41 @@ public class PromptFilesTests
     {
         Assert.EndsWith("planning-system.md", PromptFiles.PathFor(PromptKind.Planning));
     }
+
+    [Fact]
+    public void PathFor_merge_helper_kinds_map_to_their_files()
+    {
+        Assert.EndsWith("merge-helper-system.md", PromptFiles.PathFor(PromptKind.MergeHelper));
+        Assert.EndsWith("merge-helper-initial.md", PromptFiles.PathFor(PromptKind.MergeHelperInitial));
+    }
+
+    [Fact]
+    public void DefaultFor_merge_helper_is_non_empty_and_mentions_the_merge_tools()
+    {
+        var d = PromptFiles.DefaultFor(PromptKind.MergeHelper);
+        Assert.False(string.IsNullOrWhiteSpace(d));
+        Assert.Contains("review_task", d);
+        Assert.Contains("continue_merge", d);
+    }
+
+    [Fact]
+    public void DefaultFor_merge_helper_initial_has_scope_and_tasks_tokens()
+    {
+        var d = PromptFiles.DefaultFor(PromptKind.MergeHelperInitial);
+        Assert.False(string.IsNullOrWhiteSpace(d));
+        Assert.Contains("{scope}", d);
+        Assert.Contains("{tasks}", d);
+    }
+
+    [Fact]
+    public void RenderTemplate_merge_helper_initial_substitutes_scope_and_tasks()
+    {
+        var outp = PromptFiles.RenderTemplate(
+            PromptFiles.DefaultFor(PromptKind.MergeHelperInitial),
+            new Dictionary<string, string> { ["scope"] = "All lists", ["tasks"] = "- [Idle] T1" });
+        Assert.Contains("Scope: All lists", outp);
+        Assert.Contains("- [Idle] T1", outp);
+        Assert.DoesNotContain("{scope}", outp);
+        Assert.DoesNotContain("{tasks}", outp);
+    }
 }