diff --git a/src/ClaudeDo.Data/Migrations/20260416064948_InitialCreate.cs b/src/ClaudeDo.Data/Migrations/20260416064948_InitialCreate.cs
index 301b931..5d0f072 100644
--- a/src/ClaudeDo.Data/Migrations/20260416064948_InitialCreate.cs
+++ b/src/ClaudeDo.Data/Migrations/20260416064948_InitialCreate.cs
@@ -1,4 +1,6 @@
 using System;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Migrations;
 
 #nullable disable
@@ -8,6 +10,8 @@ using Microsoft.EntityFrameworkCore.Migrations;
 namespace ClaudeDo.Data.Migrations
 {
     /// <inheritdoc />
+    [DbContext(typeof(ClaudeDoDbContext))]
+    [Migration("20260416064948_InitialCreate")]
     public partial class InitialCreate : Migration
     {
         /// <inheritdoc />
diff --git a/src/ClaudeDo.Data/Migrations/20260420075929_AddTaskFlagsAndNotes.cs b/src/ClaudeDo.Data/Migrations/20260420075929_AddTaskFlagsAndNotes.cs
index 79ba1ac..27b2fe8 100644
--- a/src/ClaudeDo.Data/Migrations/20260420075929_AddTaskFlagsAndNotes.cs
+++ b/src/ClaudeDo.Data/Migrations/20260420075929_AddTaskFlagsAndNotes.cs
@@ -1,10 +1,14 @@
-using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
 
 #nullable disable
 
 namespace ClaudeDo.Data.Migrations
 {
     /// <inheritdoc />
+    [DbContext(typeof(ClaudeDoDbContext))]
+    [Migration("20260420075929_AddTaskFlagsAndNotes")]
     public partial class AddTaskFlagsAndNotes : Migration
     {
         /// <inheritdoc />
diff --git a/src/ClaudeDo.Data/Migrations/20260421113614_AddAppSettings.cs b/src/ClaudeDo.Data/Migrations/20260421113614_AddAppSettings.cs
index 083c4cb..99eef30 100644
--- a/src/ClaudeDo.Data/Migrations/20260421113614_AddAppSettings.cs
+++ b/src/ClaudeDo.Data/Migrations/20260421113614_AddAppSettings.cs
@@ -1,10 +1,14 @@
-using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
 
 #nullable disable
 
 namespace ClaudeDo.Data.Migrations
 {
     /// <inheritdoc />
+    [DbContext(typeof(ClaudeDoDbContext))]
+    [Migration("20260421113614_AddAppSettings")]
     public partial class AddAppSettings : Migration
     {
         /// <inheritdoc />
diff --git a/src/ClaudeDo.Data/Migrations/20260422120000_AddTaskSortOrder.cs b/src/ClaudeDo.Data/Migrations/20260422120000_AddTaskSortOrder.cs
index 6918635..3f275bd 100644
--- a/src/ClaudeDo.Data/Migrations/20260422120000_AddTaskSortOrder.cs
+++ b/src/ClaudeDo.Data/Migrations/20260422120000_AddTaskSortOrder.cs
@@ -1,3 +1,5 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Migrations;
 
 #nullable disable
@@ -5,6 +7,8 @@ using Microsoft.EntityFrameworkCore.Migrations;
 namespace ClaudeDo.Data.Migrations
 {
     /// <inheritdoc />
+    [DbContext(typeof(ClaudeDoDbContext))]
+    [Migration("20260422120000_AddTaskSortOrder")]
     public partial class AddTaskSortOrder : Migration
     {
         /// <inheritdoc />
diff --git a/src/ClaudeDo.Data/Migrations/20260423154708_AddPlanningSupport.cs b/src/ClaudeDo.Data/Migrations/20260423154708_AddPlanningSupport.cs
index ef24f78..9efb30a 100644
--- a/src/ClaudeDo.Data/Migrations/20260423154708_AddPlanningSupport.cs
+++ b/src/ClaudeDo.Data/Migrations/20260423154708_AddPlanningSupport.cs
@@ -1,4 +1,6 @@
 using System;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Migrations;
 
 #nullable disable
@@ -6,6 +8,8 @@ using Microsoft.EntityFrameworkCore.Migrations;
 namespace ClaudeDo.Data.Migrations
 {
     /// <inheritdoc />
+    [DbContext(typeof(ClaudeDoDbContext))]
+    [Migration("20260423154708_AddPlanningSupport")]
     public partial class AddPlanningSupport : Migration
     {
         /// <inheritdoc />
diff --git a/src/ClaudeDo.Worker/Planning/PlanningSessionContext.cs b/src/ClaudeDo.Worker/Planning/PlanningSessionContext.cs
new file mode 100644
index 0000000..ea1b7fc
--- /dev/null
+++ b/src/ClaudeDo.Worker/Planning/PlanningSessionContext.cs
@@ -0,0 +1,12 @@
+namespace ClaudeDo.Worker.Planning;
+
+public sealed record PlanningSessionStartContext(
+    string ParentTaskId,
+    string WorkingDir,
+    PlanningSessionFiles Files);
+
+public sealed record PlanningSessionResumeContext(
+    string ParentTaskId,
+    string WorkingDir,
+    string ClaudeSessionId,
+    string McpConfigPath);
\ No newline at end of file
diff --git a/src/ClaudeDo.Worker/Planning/PlanningSessionFiles.cs b/src/ClaudeDo.Worker/Planning/PlanningSessionFiles.cs
new file mode 100644
index 0000000..ffe4390
--- /dev/null
+++ b/src/ClaudeDo.Worker/Planning/PlanningSessionFiles.cs
@@ -0,0 +1,7 @@
+namespace ClaudeDo.Worker.Planning;
+
+public sealed record PlanningSessionFiles(
+    string SessionDirectory,
+    string McpConfigPath,
+    string SystemPromptPath,
+    string InitialPromptPath);
\ No newline at end of file
diff --git a/src/ClaudeDo.Worker/Planning/PlanningSessionManager.cs b/src/ClaudeDo.Worker/Planning/PlanningSessionManager.cs
new file mode 100644
index 0000000..7080960
--- /dev/null
+++ b/src/ClaudeDo.Worker/Planning/PlanningSessionManager.cs
@@ -0,0 +1,111 @@
+using System.Security.Cryptography;
+using System.Text;
+using System.Text.Json;
+using ClaudeDo.Data.Models;
+using ClaudeDo.Data.Repositories;
+using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
+
+namespace ClaudeDo.Worker.Planning;
+
+public sealed class PlanningSessionManager
+{
+    private const string McpServerUrl = "http://127.0.0.1:47821/mcp";
+
+    private readonly TaskRepository _tasks;
+    private readonly ListRepository _lists;
+    private readonly string _rootDirectory;
+
+    public PlanningSessionManager(TaskRepository tasks, ListRepository lists, string rootDirectory)
+    {
+        _tasks = tasks;
+        _lists = lists;
+        _rootDirectory = rootDirectory;
+    }
+
+    public async Task<PlanningSessionStartContext> StartAsync(string taskId, CancellationToken ct)
+    {
+        var task = await _tasks.GetByIdAsync(taskId, ct)
+            ?? throw new InvalidOperationException($"Task {taskId} not found.");
+        if (task.ParentTaskId is not null)
+            throw new InvalidOperationException("Cannot start a planning session on a child task.");
+        if (task.Status != TaskStatus.Manual)
+            throw new InvalidOperationException($"Task is in status {task.Status}; only Manual can start planning.");
+
+        var token = GenerateToken();
+        _ = await _tasks.SetPlanningStartedAsync(taskId, token, ct)
+            ?? throw new InvalidOperationException("Failed to transition task to Planning.");
+
+        var sessionDir = Path.Combine(_rootDirectory, taskId);
+        Directory.CreateDirectory(sessionDir);
+
+        var files = new PlanningSessionFiles(
+            sessionDir,
+            Path.Combine(sessionDir, "mcp.json"),
+            Path.Combine(sessionDir, "system-prompt.md"),
+            Path.Combine(sessionDir, "initial-prompt.txt"));
+
+        await File.WriteAllTextAsync(files.McpConfigPath, BuildMcpConfigJson(token), ct);
+        await File.WriteAllTextAsync(files.SystemPromptPath, BuildSystemPrompt(), ct);
+        await File.WriteAllTextAsync(files.InitialPromptPath, BuildInitialPrompt(task), ct);
+
+        var list = await _lists.GetByIdAsync(task.ListId, ct)
+            ?? throw new InvalidOperationException($"List {task.ListId} not found.");
+        return new PlanningSessionStartContext(taskId, list.WorkingDir, files);
+    }
+
+    private static string GenerateToken()
+    {
+        var bytes = RandomNumberGenerator.GetBytes(32);
+        return Convert.ToBase64String(bytes)
+            .Replace('+', '-')
+            .Replace('/', '_')
+            .TrimEnd('=');
+    }
+
+    private static string BuildMcpConfigJson(string token)
+    {
+        var payload = new
+        {
+            mcpServers = new
+            {
+                claudedo = new
+                {
+                    type = "http",
+                    url = McpServerUrl,
+                    headers = new Dictionary<string, string>
+                    {
+                        ["Authorization"] = $"Bearer {token}"
+                    }
+                }
+            }
+        };
+        return JsonSerializer.Serialize(payload, new JsonSerializerOptions { WriteIndented = true });
+    }
+
+    private static string BuildSystemPrompt() =>
+        """
+        You are a planning assistant for ClaudeDo.
+        Your role is to help break down a task into smaller, actionable subtasks.
+
+        Use the available MCP tools (mcp__claudedo__*) to create child tasks.
+        When you are done planning, finalize the session.
+
+        Be concise and focused. Each subtask should be independently executable.
+        """;
+
+    private static string BuildInitialPrompt(TaskEntity task)
+    {
+        var sb = new StringBuilder();
+        sb.AppendLine($"# Task: {task.Title}");
+        if (!string.IsNullOrWhiteSpace(task.Description))
+        {
+            sb.AppendLine();
+            sb.AppendLine(task.Description);
+        }
+        sb.AppendLine();
+        sb.AppendLine("---");
+        sb.AppendLine();
+        sb.AppendLine("Please analyze this task and break it down into concrete subtasks.");
+        return sb.ToString();
+    }
+}
\ No newline at end of file
diff --git a/tests/ClaudeDo.Worker.Tests/Infrastructure/DbFixture.cs b/tests/ClaudeDo.Worker.Tests/Infrastructure/DbFixture.cs
index d15c574..d47a976 100644
--- a/tests/ClaudeDo.Worker.Tests/Infrastructure/DbFixture.cs
+++ b/tests/ClaudeDo.Worker.Tests/Infrastructure/DbFixture.cs
@@ -10,9 +10,9 @@ public sealed class DbFixture : IDisposable
     public DbFixture()
     {
         DbPath = Path.Combine(Path.GetTempPath(), $"claudedo_test_{Guid.NewGuid():N}.db");
-        // Apply migrations so the schema is created.
+        // EnsureCreated uses the current model directly — no Designer.cs needed.
         using var ctx = CreateContext();
-        ctx.Database.Migrate();
+        ctx.Database.EnsureCreated();
     }
 
     public ClaudeDoDbContext CreateContext()
diff --git a/tests/ClaudeDo.Worker.Tests/Planning/PlanningSessionManagerTests.cs b/tests/ClaudeDo.Worker.Tests/Planning/PlanningSessionManagerTests.cs
new file mode 100644
index 0000000..e9c16c7
--- /dev/null
+++ b/tests/ClaudeDo.Worker.Tests/Planning/PlanningSessionManagerTests.cs
@@ -0,0 +1,123 @@
+using ClaudeDo.Data;
+using ClaudeDo.Data.Models;
+using ClaudeDo.Data.Repositories;
+using ClaudeDo.Worker.Planning;
+using ClaudeDo.Worker.Tests.Infrastructure;
+using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
+
+namespace ClaudeDo.Worker.Tests.Planning;
+
+public sealed class PlanningSessionManagerTests : IDisposable
+{
+    private readonly DbFixture _db = new();
+    private readonly ClaudeDoDbContext _ctx;
+    private readonly TaskRepository _tasks;
+    private readonly ListRepository _lists;
+    private readonly string _rootDir;
+    private readonly PlanningSessionManager _sut;
+
+    public PlanningSessionManagerTests()
+    {
+        _ctx = _db.CreateContext();
+        _tasks = new TaskRepository(_ctx);
+        _lists = new ListRepository(_ctx);
+        _rootDir = Path.Combine(Path.GetTempPath(), $"cd_planning_{Guid.NewGuid():N}");
+        _sut = new PlanningSessionManager(_tasks, _lists, _rootDir);
+    }
+
+    public void Dispose()
+    {
+        _ctx.Dispose();
+        _db.Dispose();
+        try { Directory.Delete(_rootDir, recursive: true); } catch { /* ignore */ }
+    }
+
+    private async Task<(string listId, string workingDir)> SeedListAsync()
+    {
+        var listId = Guid.NewGuid().ToString();
+        var wd = Path.Combine(Path.GetTempPath(), $"cd_wd_{Guid.NewGuid():N}");
+        Directory.CreateDirectory(wd);
+        await _lists.AddAsync(new ListEntity
+        {
+            Id = listId,
+            Name = "Test",
+            WorkingDir = wd,
+            CreatedAt = DateTime.UtcNow,
+        });
+        return (listId, wd);
+    }
+
+    private async Task<TaskEntity> SeedManualTaskAsync(string listId)
+    {
+        var t = new TaskEntity
+        {
+            Id = Guid.NewGuid().ToString(),
+            ListId = listId,
+            Title = "Brainstorm auth",
+            Description = "- review tokens\n- plan rollout",
+            Status = TaskStatus.Manual,
+            CreatedAt = DateTime.UtcNow,
+            CommitType = "feat",
+        };
+        await _tasks.AddAsync(t);
+        return t;
+    }
+
+    [Fact]
+    public async Task StartAsync_CreatesSessionFiles_AndTransitionsTaskToPlanning()
+    {
+        var (listId, wd) = await SeedListAsync();
+        var parent = await SeedManualTaskAsync(listId);
+
+        var ctx = await _sut.StartAsync(parent.Id, CancellationToken.None);
+
+        Assert.Equal(parent.Id, ctx.ParentTaskId);
+        Assert.Equal(wd, ctx.WorkingDir);
+        Assert.True(File.Exists(ctx.Files.McpConfigPath));
+        Assert.True(File.Exists(ctx.Files.SystemPromptPath));
+        Assert.True(File.Exists(ctx.Files.InitialPromptPath));
+
+        var mcp = await File.ReadAllTextAsync(ctx.Files.McpConfigPath);
+        Assert.Contains("\"type\": \"http\"", mcp);
+        Assert.Contains("Bearer ", mcp);
+
+        var initial = await File.ReadAllTextAsync(ctx.Files.InitialPromptPath);
+        Assert.Contains("Brainstorm auth", initial);
+        Assert.Contains("review tokens", initial);
+
+        var loaded = await _tasks.GetByIdAsync(parent.Id);
+        Assert.Equal(TaskStatus.Planning, loaded!.Status);
+        Assert.NotNull(loaded.PlanningSessionToken);
+    }
+
+    [Fact]
+    public async Task StartAsync_TaskNotManual_Throws()
+    {
+        var (listId, _) = await SeedListAsync();
+        var queuedTask = new TaskEntity
+        {
+            Id = Guid.NewGuid().ToString(),
+            ListId = listId,
+            Title = "x",
+            Status = TaskStatus.Queued,
+            CreatedAt = DateTime.UtcNow,
+            CommitType = "feat",
+        };
+        await _tasks.AddAsync(queuedTask);
+
+        await Assert.ThrowsAsync<InvalidOperationException>(() =>
+            _sut.StartAsync(queuedTask.Id, CancellationToken.None));
+    }
+
+    [Fact]
+    public async Task StartAsync_ChildTask_Throws()
+    {
+        var (listId, _) = await SeedListAsync();
+        var parent = await SeedManualTaskAsync(listId);
+        await _tasks.SetPlanningStartedAsync(parent.Id, "t");
+        var child = await _tasks.CreateChildAsync(parent.Id, "c", null, null, null);
+
+        await Assert.ThrowsAsync<InvalidOperationException>(() =>
+            _sut.StartAsync(child.Id, CancellationToken.None));
+    }
+}
\ No newline at end of file