feat(claude-do): MCP surface: worktree/diff/merge/log tools + status-enum doc

BUNDLE — all changes live in src/ClaudeDo.Worker/External/ExternalMcpService.cs only, so this is one worktree / one merge. Do NOT touch run-recording or data-layer code (those are separate tasks). Reuse the existing services behind the UI modals (WorktreesOverviewModalView, DiffModalView, MergeModalView) — do not reimplement git plumbing. Build green after each addition.

Add these MCP tools:
1. g

ClaudeDo-Task: f6bdfb5b-8cbf-4e65-93d4-6c758a160484

src/ClaudeDo.Worker/External/ExternalMcpService.cs

@@ -1,9 +1,15 @@
 using System.ComponentModel;
+using System.Diagnostics;
+using ClaudeDo.Data;
+using ClaudeDo.Data.Git;
 using ClaudeDo.Data.Models;
 using ClaudeDo.Data.Repositories;
 using ClaudeDo.Worker.Hub;
+using ClaudeDo.Worker.Lifecycle;
 using ClaudeDo.Worker.Queue;
 using ClaudeDo.Worker.State;
+using ClaudeDo.Worker.Worktrees;
+using Microsoft.EntityFrameworkCore;
 using ModelContextProtocol.Server;
 using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
 
@@ -12,6 +18,7 @@ namespace ClaudeDo.Worker.External;
 public sealed record TaskListDto(string Id, string Name, string? WorkingDir);
 public sealed record DeleteTaskResult(bool Deleted, string Id);
 public sealed record CancelTaskResult(bool Cancelled, string Id);
+public sealed record StatusValueDto(string Status, string Meaning);
 
 public sealed record TaskDto(
     string Id,
@@ -25,6 +32,23 @@ public sealed record TaskDto(
     DateTime? StartedAt,
     DateTime? FinishedAt);
 
+public sealed record WorktreeInfoDto(
+    string Path, string Branch, string HeadCommit, string BaseCommit,
+    int Ahead, int Behind, bool IsDirty);
+
+public sealed record TaskDiffDto(
+    string Content, IReadOnlyList<string> Files, bool Truncated, int TotalBytes);
+
+public sealed record MergeTaskResultDto(
+    bool Merged, string? MergeCommit, IReadOnlyList<string> Conflicts);
+
+public sealed record WorktreeListItemDto(
+    string? TaskId, string Path, string Branch,
+    string HeadCommit, bool IsDirty, bool MergedIntoMain);
+
+public sealed record CleanupWorktreeResult(
+    bool Removed, string WorktreePath, bool BranchDeleted);
+
 [McpServerToolType]
 public sealed class ExternalMcpService
 {
@@ -33,19 +57,31 @@ public sealed class ExternalMcpService
     private readonly QueueService _queue;
     private readonly HubBroadcaster _broadcaster;
     private readonly ITaskStateService _state;
+    private readonly GitService _git;
+    private readonly IDbContextFactory<ClaudeDoDbContext> _dbFactory;
+    private readonly WorktreeMaintenanceService _maintenance;
+    private readonly TaskMergeService _merge;
 
     public ExternalMcpService(
         TaskRepository tasks,
         ListRepository lists,
         QueueService queue,
         HubBroadcaster broadcaster,
-        ITaskStateService state)
+        ITaskStateService state,
+        GitService git,
+        IDbContextFactory<ClaudeDoDbContext> dbFactory,
+        WorktreeMaintenanceService maintenance,
+        TaskMergeService merge)
     {
         _tasks = tasks;
         _lists = lists;
         _queue = queue;
         _broadcaster = broadcaster;
         _state = state;
+        _git = git;
+        _dbFactory = dbFactory;
+        _maintenance = maintenance;
+        _merge = merge;
     }
 
     [McpServerTool, Description("List all task lists available in ClaudeDo.")]
@@ -55,7 +91,9 @@ public sealed class ExternalMcpService
         return lists.Select(l => new TaskListDto(l.Id, l.Name, l.WorkingDir)).ToList();
     }
 
-    [McpServerTool, Description("List tasks in a given list. Optionally filter by creator (CreatedBy) and/or status.")]
+    [McpServerTool, Description(
+        "List tasks in a given list. Optionally filter by creator (createdBy) and/or status. " +
+        "Valid status values: Idle, Queued, Running, Done, Failed, Cancelled.")]
     public async Task<IReadOnlyList<TaskDto>> ListTasks(
         string listId,
         string? createdBy,
@@ -66,7 +104,8 @@ public sealed class ExternalMcpService
         if (!string.IsNullOrWhiteSpace(status))
         {
             if (!Enum.TryParse<TaskStatus>(status, ignoreCase: true, out var parsed))
-                throw new InvalidOperationException($"Unknown status '{status}'.");
+                throw new InvalidOperationException(
+                    $"Unknown status '{status}'. Valid values: Idle, Queued, Running, Done, Failed, Cancelled.");
             statusFilter = parsed;
         }
 
@@ -80,7 +119,10 @@ public sealed class ExternalMcpService
         return query.Select(ToDto).ToList();
     }
 
-    [McpServerTool, Description("Get a single task by id, including its current status and result.")]
+    [McpServerTool, Description(
+        "Get a single task by id, including its current status and result. " +
+        "Status lifecycle: Idle → Queued → Running → Done | Failed | Cancelled. " +
+        "Done/Failed/Cancelled tasks can be reset to Idle for re-execution.")]
     public async Task<TaskDto> GetTask(string taskId, CancellationToken cancellationToken)
     {
         var task = await _tasks.GetByIdAsync(taskId, cancellationToken)
@@ -120,7 +162,6 @@ public sealed class ExternalMcpService
 
         if (queueImmediately)
         {
-            // Routes through TaskStateService so the queue is woken automatically.
             var enqueue = await _state.EnqueueAsync(entity.Id, cancellationToken);
             if (!enqueue.Ok)
                 throw new InvalidOperationException(enqueue.Reason ?? "Cannot enqueue task.");
@@ -154,14 +195,19 @@ public sealed class ExternalMcpService
         return ToDto(reload);
     }
 
-    [McpServerTool, Description("Update a task's status. Only 'Idle' and 'Queued' are permitted — use RunTaskNow or CancelTask for execution control.")]
+    [McpServerTool, Description(
+        "Update a task's status. Only 'Idle' and 'Queued' are permitted externally — " +
+        "use run_task_now or cancel_task for execution control. " +
+        "Settable: Idle (reset to editable), Queued (enqueue for execution). " +
+        "Full lifecycle: Idle → Queued → Running → Done | Failed | Cancelled.")]
     public async Task<TaskDto> UpdateTaskStatus(
         string taskId,
         string status,
         CancellationToken cancellationToken)
     {
         if (!Enum.TryParse<TaskStatus>(status, ignoreCase: true, out var target))
-            throw new InvalidOperationException($"Unknown status '{status}'.");
+            throw new InvalidOperationException(
+                $"Unknown status '{status}'. Valid values: Idle, Queued, Running, Done, Failed, Cancelled.");
 
         var task = await _tasks.GetByIdAsync(taskId, cancellationToken)
             ?? throw new InvalidOperationException($"Task {taskId} not found.");
@@ -181,7 +227,7 @@ public sealed class ExternalMcpService
 
             default:
                 throw new InvalidOperationException(
-                    $"Status '{target}' is not settable externally. Use RunTaskNow or CancelTask.");
+                    $"Status '{target}' is not settable externally. Use run_task_now or cancel_task.");
         }
 
         var reload = (await _tasks.GetByIdAsync(taskId, cancellationToken))!;
@@ -227,6 +273,256 @@ public sealed class ExternalMcpService
         return new DeleteTaskResult(true, taskId);
     }
 
+    // ── Status reference ─────────────────────────────────────────────────────
+
+    [McpServerTool, Description("Returns all valid task status values and their meanings. Use before filtering by status or interpreting task state.")]
+    public Task<IReadOnlyList<StatusValueDto>> GetTaskStatusValues() =>
+        Task.FromResult<IReadOnlyList<StatusValueDto>>([
+            new("Idle",      "Not yet queued; task is editable and will not run until enqueued."),
+            new("Queued",    "Waiting for an agent execution slot. Tasks with a blocker (BlockedByTaskId) are skipped by the queue picker until their predecessor finishes."),
+            new("Running",   "Agent is actively executing the task; cannot be edited or deleted until cancelled."),
+            new("Done",      "Completed successfully; result text is available in the result field. Can be reset to Idle for re-execution."),
+            new("Failed",    "Execution ended with an error; task can be reset to Idle or re-queued directly."),
+            new("Cancelled", "Cancelled by the user; task can be reset to Idle or re-queued directly."),
+        ]);
+
+    // ── Worktree / git tools ──────────────────────────────────────────────────
+
+    [McpServerTool, Description(
+        "Get git worktree details for a task: path, branch, headCommit (current HEAD SHA), " +
+        "baseCommit (SHA where the branch was created), ahead (commits on branch since base), " +
+        "behind (commits on main not yet on this branch; 0 if 'main' ref is unreachable), " +
+        "isDirty (has uncommitted changes in the worktree directory). " +
+        "Throws if the task or its worktree does not exist.")]
+    public async Task<WorktreeInfoDto> GetTaskWorktree(string taskId, CancellationToken cancellationToken)
+    {
+        var (_, _, wt) = await LoadWorktreeContextAsync(taskId, cancellationToken);
+
+        var headCommit = !string.IsNullOrWhiteSpace(wt.HeadCommit)
+            ? wt.HeadCommit
+            : await TryRunGitAsync(wt.Path, ["rev-parse", "HEAD"], cancellationToken) ?? wt.BaseCommit;
+
+        var isDirty = Directory.Exists(wt.Path) && await _git.HasChangesAsync(wt.Path, cancellationToken);
+        var ahead  = await GitRevListCountAsync(wt.Path, $"{wt.BaseCommit}..HEAD", cancellationToken);
+        var behind = await GitRevListCountAsync(wt.Path, "HEAD..main", cancellationToken);
+
+        return new WorktreeInfoDto(wt.Path, wt.BranchName, headCommit!, wt.BaseCommit, ahead, behind, isDirty);
+    }
+
+    [McpServerTool, Description(
+        "Get the diff for a task's worktree relative to its base commit. " +
+        "stat=false (default): returns the full unified diff, capped at 200 KB (truncated=true when larger). " +
+        "stat=true: returns a --stat summary (changed files with insertion/deletion counts). " +
+        "files always lists the changed file paths regardless of stat mode. " +
+        "totalBytes is the uncapped diff size (useful when truncated=true). " +
+        "Throws if the task has no worktree or the worktree directory is missing from disk.")]
+    public async Task<TaskDiffDto> GetTaskDiff(
+        string taskId, bool stat = false, CancellationToken cancellationToken = default)
+    {
+        var (_, _, wt) = await LoadWorktreeContextAsync(taskId, cancellationToken);
+
+        if (!Directory.Exists(wt.Path))
+            throw new InvalidOperationException($"Worktree directory does not exist on disk: {wt.Path}");
+
+        const int maxBytes = 200 * 1024;
+
+        if (stat)
+        {
+            var diffStat = await _git.DiffStatAsync(wt.Path, wt.BaseCommit, "HEAD", cancellationToken);
+            return new TaskDiffDto(diffStat, ParseDiffStatFileNames(diffStat), false, diffStat.Length);
+        }
+
+        var diff = await _git.GetBranchDiffAsync(wt.Path, wt.BaseCommit, cancellationToken);
+        var files = ParseDiffFileNames(diff);
+
+        if (diff.Length <= maxBytes)
+            return new TaskDiffDto(diff, files, false, diff.Length);
+
+        return new TaskDiffDto(diff[..maxBytes], files, true, diff.Length);
+    }
+
+    [McpServerTool, Description(
+        "Merge a task's worktree branch into targetBranch (default: main). " +
+        "noFf=true (default): always creates a merge commit (--no-ff). " +
+        "dryRun=true: validates preconditions only, does not perform the merge; merged=false in the result means 'not actually merged'. " +
+        "Refuses if task status is not Done (status values: Idle, Queued, Running, Done, Failed, Cancelled). " +
+        "On success: merged=true, mergeCommit contains the new merge commit SHA. " +
+        "On conflict: the merge is cleanly aborted (no half-merged state left); merged=false and conflicts lists the affected files.")]
+    public async Task<MergeTaskResultDto> MergeTask(
+        string taskId,
+        string targetBranch = "main",
+        bool noFf = true,
+        bool dryRun = false,
+        CancellationToken cancellationToken = default)
+    {
+        var task = await _tasks.GetByIdAsync(taskId, cancellationToken)
+            ?? throw new InvalidOperationException($"Task {taskId} not found.");
+        if (task.Status != TaskStatus.Done)
+            throw new InvalidOperationException(
+                $"Task must be Done to merge (current status: {task.Status}). " +
+                "Valid statuses for merge: Done.");
+
+        var list = await _lists.GetByIdAsync(task.ListId, cancellationToken);
+
+        if (dryRun)
+        {
+            using var ctx = _dbFactory.CreateDbContext();
+            var wt = await new WorktreeRepository(ctx).GetByTaskIdAsync(taskId, cancellationToken)
+                ?? throw new InvalidOperationException($"Task {taskId} has no worktree.");
+            if (wt.State != WorktreeState.Active)
+                throw new InvalidOperationException(
+                    $"Worktree state must be Active to merge (current: {wt.State}).");
+            return new MergeTaskResultDto(false, null, []);
+        }
+
+        var commitMessage = $"Merge task branch for: {task.Title}";
+        var result = await _merge.MergeAsync(
+            taskId, targetBranch, removeWorktree: false, commitMessage, cancellationToken);
+
+        if (result.Status == TaskMergeService.StatusMerged)
+        {
+            string? mergeCommit = null;
+            try
+            {
+                if (!string.IsNullOrWhiteSpace(list?.WorkingDir) && Directory.Exists(list.WorkingDir))
+                    mergeCommit = await _git.RevParseHeadAsync(list.WorkingDir, cancellationToken);
+            }
+            catch { /* mergeCommit is optional */ }
+            return new MergeTaskResultDto(true, mergeCommit, []);
+        }
+
+        if (result.Status == TaskMergeService.StatusConflict)
+            return new MergeTaskResultDto(false, null, result.ConflictFiles);
+
+        throw new InvalidOperationException(result.ErrorMessage ?? $"Merge blocked: {result.Status}");
+    }
+
+    [McpServerTool, Description(
+        "List all ClaudeDo-tracked worktrees. " +
+        "Each entry: taskId, path, branch, headCommit (empty if path missing on disk), " +
+        "isDirty (has uncommitted changes), mergedIntoMain (worktree state is Merged). " +
+        "Only worktrees recorded in the ClaudeDo database are returned.")]
+    public async Task<IReadOnlyList<WorktreeListItemDto>> ListWorktrees(CancellationToken cancellationToken)
+    {
+        var rows = await _maintenance.GetOverviewAsync(null, cancellationToken);
+        var results = await Task.WhenAll(rows.Select(async row =>
+        {
+            var isDirty = row.PathExistsOnDisk && await TryGetIsDirtyAsync(row.Path, cancellationToken);
+            var headCommit = row.PathExistsOnDisk
+                ? (await TryRunGitAsync(row.Path, ["rev-parse", "HEAD"], cancellationToken) ?? "")
+                : "";
+            return new WorktreeListItemDto(
+                row.TaskId, row.Path, row.BranchName, headCommit,
+                isDirty, row.State == WorktreeState.Merged);
+        }));
+        return results;
+    }
+
+    [McpServerTool, Description(
+        "Remove a task's worktree directory and delete its git branch. " +
+        "force=false (default): refuses if the worktree has uncommitted changes or the task is Running. " +
+        "force=true: removes even a dirty worktree (uncommitted changes are lost); task must not be Running. " +
+        "Returns removed=true on success; branchDeleted reflects whether the branch was also removed.")]
+    public async Task<CleanupWorktreeResult> CleanupTaskWorktree(
+        string taskId, bool force = false, CancellationToken cancellationToken = default)
+    {
+        using var ctx = _dbFactory.CreateDbContext();
+        var task = await new TaskRepository(ctx).GetByIdAsync(taskId, cancellationToken)
+            ?? throw new InvalidOperationException($"Task {taskId} not found.");
+        var wt = await new WorktreeRepository(ctx).GetByTaskIdAsync(taskId, cancellationToken)
+            ?? throw new InvalidOperationException($"Task {taskId} has no worktree.");
+
+        if (task.Status == TaskStatus.Running)
+            throw new InvalidOperationException("Cannot remove worktree of a running task.");
+
+        if (!force && Directory.Exists(wt.Path))
+        {
+            var isDirty = await _git.HasChangesAsync(wt.Path, cancellationToken);
+            if (isDirty)
+                throw new InvalidOperationException(
+                    "Worktree has uncommitted changes. Use force=true to remove anyway (changes will be lost).");
+        }
+
+        var path = wt.Path;
+        var result = await _maintenance.ForceRemoveAsync(taskId, cancellationToken);
+        return new CleanupWorktreeResult(result.Removed, path, result.Removed);
+    }
+
+    // ── Private helpers ───────────────────────────────────────────────────────
+
+    private async Task<(TaskEntity Task, ListEntity List, WorktreeEntity Wt)> LoadWorktreeContextAsync(
+        string taskId, CancellationToken ct)
+    {
+        using var ctx = _dbFactory.CreateDbContext();
+        var task = await new TaskRepository(ctx).GetByIdAsync(taskId, ct)
+            ?? throw new InvalidOperationException($"Task {taskId} not found.");
+        var list = await new ListRepository(ctx).GetByIdAsync(task.ListId, ct)
+            ?? throw new InvalidOperationException("List not found.");
+        var wt = await new WorktreeRepository(ctx).GetByTaskIdAsync(taskId, ct)
+            ?? throw new InvalidOperationException($"Task {taskId} has no worktree.");
+        return (task, list, wt);
+    }
+
+    private async Task<bool> TryGetIsDirtyAsync(string path, CancellationToken ct)
+    {
+        try { return await _git.HasChangesAsync(path, ct); }
+        catch { return false; }
+    }
+
+    // Minimal git runner for operations not covered by GitService (rev-list --count, rev-parse from worktree).
+    private static async Task<string?> TryRunGitAsync(string dir, string[] args, CancellationToken ct)
+    {
+        try
+        {
+            var psi = new ProcessStartInfo("git")
+            {
+                UseShellExecute = false,
+                RedirectStandardOutput = true,
+                CreateNoWindow = true,
+            };
+            psi.ArgumentList.Add("-C");
+            psi.ArgumentList.Add(dir);
+            foreach (var a in args) psi.ArgumentList.Add(a);
+            using var proc = Process.Start(psi)!;
+            await using var _ = ct.Register(() => { try { proc.Kill(entireProcessTree: true); } catch { } });
+            var stdout = await proc.StandardOutput.ReadToEndAsync();
+            await proc.WaitForExitAsync(CancellationToken.None);
+            ct.ThrowIfCancellationRequested();
+            return proc.ExitCode == 0 ? stdout.Trim() : null;
+        }
+        catch (OperationCanceledException) { throw; }
+        catch { return null; }
+    }
+
+    private static async Task<int> GitRevListCountAsync(string dir, string range, CancellationToken ct)
+    {
+        var result = await TryRunGitAsync(dir, ["rev-list", "--count", range], ct);
+        return int.TryParse(result, out var n) ? n : 0;
+    }
+
+    private static IReadOnlyList<string> ParseDiffFileNames(string diff)
+    {
+        var files = new List<string>();
+        foreach (var line in diff.Split('\n'))
+        {
+            var s = line.TrimEnd('\r');
+            if (s.StartsWith("+++ b/", StringComparison.Ordinal))
+                files.Add(s[6..]);
+        }
+        return files;
+    }
+
+    private static IReadOnlyList<string> ParseDiffStatFileNames(string stat)
+    {
+        var files = new List<string>();
+        foreach (var line in stat.Split('\n'))
+        {
+            var idx = line.IndexOf('|');
+            if (idx > 0) files.Add(line[..idx].Trim());
+        }
+        return files;
+    }
+
     private static TaskDto ToDto(TaskEntity t) => new(
         t.Id,
         t.ListId,

src/ClaudeDo.Worker/External/RunHistoryMcpTools.cs

@@ -11,6 +11,12 @@ public sealed record RunDto(
     int? ExitCode, int? TurnCount, int? TokensIn, int? TokensOut,
     DateTime? StartedAt, DateTime? FinishedAt);
 
+public sealed record TaskLogResult(
+    bool Available,
+    IReadOnlyList<string> Entries,
+    int TotalLines,
+    bool Truncated);
+
 [McpServerToolType]
 public sealed class RunHistoryMcpTools
 {
@@ -33,26 +39,68 @@ public sealed class RunHistoryMcpTools
         return ToDto(run);
     }
 
-    private const int MaxLogBytes = 256 * 1024;
+    [McpServerTool, Description(
-
+        "Fetch log entries from a task's latest run. " +
-    [McpServerTool, Description("Fetch the raw log output of a task's latest run. Throws if no log is available.")]
+        "Returns { available, entries, totalLines, truncated }. " +
-    public async Task<string> GetTaskLog(string taskId, CancellationToken cancellationToken)
+        "available=false means no log exists yet (task is queued or just started — not an error). " +
+        "entries are the individual lines (NDJSON messages) from Claude's streaming output. " +
+        "Default: returns the last 50 entries (tail=50). " +
+        "tail: override the number of trailing entries to return. " +
+        "offset+limit: return entries starting at position offset (0-based); overrides tail when provided. " +
+        "truncated=true when fewer entries are returned than totalLines.")]
+    public async Task<TaskLogResult> GetTaskLog(
+        string taskId,
+        int? tail = null,
+        int? offset = null,
+        int? limit = null,
+        CancellationToken cancellationToken = default)
     {
-        var run = await _runs.GetLatestByTaskIdAsync(taskId, cancellationToken)
+        var run = await _runs.GetLatestByTaskIdAsync(taskId, cancellationToken);
-            ?? throw new InvalidOperationException($"No runs found for task {taskId}.");
+        if (run is null || string.IsNullOrWhiteSpace(run.LogPath) || !File.Exists(run.LogPath))
-        if (string.IsNullOrWhiteSpace(run.LogPath) || !File.Exists(run.LogPath))
+            return new TaskLogResult(false, [], 0, false);
-            throw new InvalidOperationException("No log available for the latest run.");
 
-        var totalBytes = new FileInfo(run.LogPath).Length;
+        string allText;
-        if (totalBytes <= MaxLogBytes)
+        try
-            return await File.ReadAllTextAsync(run.LogPath, cancellationToken);
+        {
+            await using var fs = new FileStream(
+                run.LogPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
+            using var reader = new StreamReader(fs);
+            allText = await reader.ReadToEndAsync(cancellationToken);
+        }
+        catch (IOException)
+        {
+            return new TaskLogResult(false, [], 0, false);
+        }
 
-        var buffer = new byte[MaxLogBytes];
+        var lines = allText.Split(new[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries);
-        await using var fs = new FileStream(run.LogPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
+        var totalLines = lines.Length;
-        fs.Seek(totalBytes - MaxLogBytes, SeekOrigin.Begin);
+
-        var read = await fs.ReadAsync(buffer, cancellationToken);
+        IReadOnlyList<string> entries;
-        var tail = System.Text.Encoding.UTF8.GetString(buffer, 0, read);
+        bool truncated;
-        return $"[truncated: showing last {MaxLogBytes} of {totalBytes} bytes]\n{tail}";
+
+        if (offset.HasValue || limit.HasValue)
+        {
+            var start = Math.Max(0, offset ?? 0);
+            var count = limit.HasValue ? Math.Min(limit.Value, totalLines - start) : totalLines - start;
+            entries = lines.Skip(start).Take(count).ToArray();
+            truncated = start > 0 || (start + count) < totalLines;
+        }
+        else
+        {
+            var take = tail ?? 50;
+            if (totalLines <= take)
+            {
+                entries = lines;
+                truncated = false;
+            }
+            else
+            {
+                entries = lines[^take..];
+                truncated = true;
+            }
+        }
+
+        return new TaskLogResult(true, entries, totalLines, truncated);
     }
 
     private static RunDto ToDto(TaskRunEntity r) => new(

src/ClaudeDo.Worker/Program.cs

@@ -204,6 +204,9 @@ if (cfg.ExternalMcpPort > 0)
     externalBuilder.Services.AddSingleton(app.Services.GetRequiredService<WorktreeManager>());
     externalBuilder.Services.AddSingleton(app.Services.GetRequiredService<AgentFileService>());
     externalBuilder.Services.AddSingleton(app.Services.GetRequiredService<TaskResetService>());
+    externalBuilder.Services.AddSingleton(app.Services.GetRequiredService<GitService>());
+    externalBuilder.Services.AddSingleton(app.Services.GetRequiredService<WorktreeMaintenanceService>());
+    externalBuilder.Services.AddSingleton(app.Services.GetRequiredService<TaskMergeService>());
     externalBuilder.Services.AddScoped<ExternalMcpService>();
     externalBuilder.Services.AddScoped<ListMcpTools>();
     externalBuilder.Services.AddScoped<ConfigMcpTools>();

tests/ClaudeDo.Worker.Tests/External/ExternalMcpServiceTests.cs

@@ -5,10 +5,12 @@ using ClaudeDo.Data.Repositories;
 using ClaudeDo.Worker.Config;
 using ClaudeDo.Worker.External;
 using ClaudeDo.Worker.Hub;
+using ClaudeDo.Worker.Lifecycle;
 using ClaudeDo.Worker.Queue;
 using ClaudeDo.Worker.Runner;
 using ClaudeDo.Worker.Tests.Infrastructure;
 using ClaudeDo.Worker.Tests.Services;
+using ClaudeDo.Worker.Worktrees;
 using Microsoft.AspNetCore.SignalR;
 using Microsoft.Extensions.Logging.Abstractions;
 using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
@@ -87,9 +89,17 @@ public sealed class ExternalMcpServiceTests : IDisposable
         return task;
     }
 
-    private ExternalMcpService BuildSut(QueueService queue) =>
+    private ExternalMcpService BuildSut(QueueService queue)
-        new(_tasks, _lists, queue, _broadcaster,
+    {
-            TaskStateServiceBuilder.Build(_db.CreateFactory()).State);
+        var git = new GitService();
+        var factory = _db.CreateFactory();
+        var maintenance = new WorktreeMaintenanceService(factory, git, NullLogger<WorktreeMaintenanceService>.Instance);
+        var merge = new TaskMergeService(factory, git, _broadcaster, NullLogger<TaskMergeService>.Instance);
+        return new ExternalMcpService(
+            _tasks, _lists, queue, _broadcaster,
+            TaskStateServiceBuilder.Build(factory).State,
+            git, factory, maintenance, merge);
+    }
 
     private QueueService CreateQueue()
     {

tests/ClaudeDo.Worker.Tests/External/RunHistoryMcpToolsTests.cs

@@ -54,13 +54,16 @@ public sealed class RunHistoryMcpToolsTests : IDisposable
     }
 
     [Fact]
-    public async Task GetTaskLog_NoLog_Throws()
+    public async Task GetTaskLog_NoRun_ReturnsUnavailable()
     {
         var taskId = Guid.NewGuid().ToString();
         await SeedTaskAsync(taskId);
 
-        await Assert.ThrowsAsync<InvalidOperationException>(() =>
+        var result = await _sut.GetTaskLog(taskId, cancellationToken: CancellationToken.None);
-            _sut.GetTaskLog(taskId, CancellationToken.None));
+
+        Assert.False(result.Available);
+        Assert.Empty(result.Entries);
+        Assert.Equal(0, result.TotalLines);
     }
 
     [Fact]
@@ -69,24 +72,26 @@ public sealed class RunHistoryMcpToolsTests : IDisposable
         var taskId = Guid.NewGuid().ToString();
         await SeedTaskAsync(taskId);
         var logPath = Path.Combine(Path.GetTempPath(), $"claudedo_log_{Guid.NewGuid():N}.txt");
-        await File.WriteAllTextAsync(logPath, "hello log");
+        await File.WriteAllTextAsync(logPath, "line1\nline2\nline3");
         await _runs.AddAsync(new TaskRunEntity
         {
             Id = Guid.NewGuid().ToString(), TaskId = taskId, RunNumber = 1,
             IsRetry = false, Prompt = "p", LogPath = logPath,
         });
 
-        string content;
+        TaskLogResult result;
         try
         {
-            content = await _sut.GetTaskLog(taskId, CancellationToken.None);
+            result = await _sut.GetTaskLog(taskId, cancellationToken: CancellationToken.None);
         }
         finally
         {
             File.Delete(logPath);
         }
 
-        Assert.Equal("hello log", content);
+        Assert.True(result.Available);
+        Assert.Equal(3, result.TotalLines);
+        Assert.Contains("line1", result.Entries);
     }
 
     [Fact]
@@ -97,7 +102,7 @@ public sealed class RunHistoryMcpToolsTests : IDisposable
     }
 
     [Fact]
-    public async Task GetTaskLog_RunExistsButNoLogPath_Throws()
+    public async Task GetTaskLog_RunExistsButNoLogPath_ReturnsUnavailable()
     {
         var taskId = Guid.NewGuid().ToString();
         await SeedTaskAsync(taskId);
@@ -107,22 +112,22 @@ public sealed class RunHistoryMcpToolsTests : IDisposable
             IsRetry = false, Prompt = "p", LogPath = null,
         });
 
-        await Assert.ThrowsAsync<InvalidOperationException>(() =>
+        var result = await _sut.GetTaskLog(taskId, cancellationToken: CancellationToken.None);
-            _sut.GetTaskLog(taskId, CancellationToken.None));
+
+        Assert.False(result.Available);
+        Assert.Empty(result.Entries);
     }
 
     [Fact]
-    public async Task GetTaskLog_LargeFile_ReturnsTruncatedTail()
+    public async Task GetTaskLog_ManyLines_DefaultTailReturnsLast50()
     {
         var taskId = Guid.NewGuid().ToString();
         await SeedTaskAsync(taskId);
         var logPath = Path.Combine(Path.GetTempPath(), $"claudedo_log_{Guid.NewGuid():N}.txt");
 
-        // Write 300 KB so it exceeds the 256 KB cap
+        // Write 108 lines (the observed real-world size that exceeded token limits)
-        var chunk = new string('A', 1024);
+        var lines = Enumerable.Range(1, 108).Select(i => $"{{\"line\":{i}}}");
-        await using (var w = new StreamWriter(logPath, append: false))
+        await File.WriteAllLinesAsync(logPath, lines);
-            for (var i = 0; i < 300; i++)
-                await w.WriteAsync(chunk);
 
         await _runs.AddAsync(new TaskRunEntity
         {
@@ -130,17 +135,84 @@ public sealed class RunHistoryMcpToolsTests : IDisposable
             IsRetry = false, Prompt = "p", LogPath = logPath,
         });
 
-        string content;
+        TaskLogResult result;
         try
         {
-            content = await _sut.GetTaskLog(taskId, CancellationToken.None);
+            result = await _sut.GetTaskLog(taskId, cancellationToken: CancellationToken.None);
         }
         finally
         {
             File.Delete(logPath);
         }
 
-        Assert.StartsWith("[truncated:", content);
+        Assert.True(result.Available);
-        Assert.True(content.Length < 300 * 1024);
+        Assert.True(result.Truncated);
+        Assert.Equal(108, result.TotalLines);
+        Assert.Equal(50, result.Entries.Count);
+        Assert.Contains("{\"line\":108}", result.Entries);    // last line is present
+        Assert.DoesNotContain("{\"line\":1}", result.Entries); // first line is not
+    }
+
+    [Fact]
+    public async Task GetTaskLog_TailParam_ReturnsRequestedCount()
+    {
+        var taskId = Guid.NewGuid().ToString();
+        await SeedTaskAsync(taskId);
+        var logPath = Path.Combine(Path.GetTempPath(), $"claudedo_log_{Guid.NewGuid():N}.txt");
+        var lines = Enumerable.Range(1, 20).Select(i => $"line{i}");
+        await File.WriteAllLinesAsync(logPath, lines);
+
+        await _runs.AddAsync(new TaskRunEntity
+        {
+            Id = Guid.NewGuid().ToString(), TaskId = taskId, RunNumber = 1,
+            IsRetry = false, Prompt = "p", LogPath = logPath,
+        });
+
+        TaskLogResult result;
+        try
+        {
+            result = await _sut.GetTaskLog(taskId, tail: 5, cancellationToken: CancellationToken.None);
+        }
+        finally
+        {
+            File.Delete(logPath);
+        }
+
+        Assert.True(result.Available);
+        Assert.True(result.Truncated);
+        Assert.Equal(5, result.Entries.Count);
+        Assert.Equal("line20", result.Entries[^1]);
+    }
+
+    [Fact]
+    public async Task GetTaskLog_OffsetLimit_ReturnsSlice()
+    {
+        var taskId = Guid.NewGuid().ToString();
+        await SeedTaskAsync(taskId);
+        var logPath = Path.Combine(Path.GetTempPath(), $"claudedo_log_{Guid.NewGuid():N}.txt");
+        var lines = Enumerable.Range(1, 10).Select(i => $"line{i}");
+        await File.WriteAllLinesAsync(logPath, lines);
+
+        await _runs.AddAsync(new TaskRunEntity
+        {
+            Id = Guid.NewGuid().ToString(), TaskId = taskId, RunNumber = 1,
+            IsRetry = false, Prompt = "p", LogPath = logPath,
+        });
+
+        TaskLogResult result;
+        try
+        {
+            result = await _sut.GetTaskLog(taskId, offset: 2, limit: 3, cancellationToken: CancellationToken.None);
+        }
+        finally
+        {
+            File.Delete(logPath);
+        }
+
+        Assert.True(result.Available);
+        Assert.Equal(3, result.Entries.Count);
+        Assert.Equal("line3", result.Entries[0]);
+        Assert.Equal("line5", result.Entries[^1]);
+        Assert.True(result.Truncated);
     }
 }