diff --git a/src/ClaudeDo.App/Program.cs b/src/ClaudeDo.App/Program.cs
index 8d274af..1757351 100644
--- a/src/ClaudeDo.App/Program.cs
+++ b/src/ClaudeDo.App/Program.cs
@@ -2,6 +2,7 @@ using Avalonia;
 using ClaudeDo.Data;
 using ClaudeDo.Data.Git;
 using ClaudeDo.Data.Repositories;
+using ClaudeDo.Data.Seeding;
 using ClaudeDo.Ui;
 using ClaudeDo.Ui.Services;
 using ClaudeDo.Ui.ViewModels;
@@ -28,8 +29,9 @@ sealed class Program
 
         using (var scope = services.CreateScope())
         {
-            ClaudeDoDbContext.MigrateAndConfigure(
-                scope.ServiceProvider.GetRequiredService<ClaudeDoDbContext>());
+            var db = scope.ServiceProvider.GetRequiredService<ClaudeDoDbContext>();
+            ClaudeDoDbContext.MigrateAndConfigure(db);
+            DefaultListsSeeder.SeedAsync(db).GetAwaiter().GetResult();
         }
 
         try
diff --git a/src/ClaudeDo.Data/Seeding/DefaultListsSeeder.cs b/src/ClaudeDo.Data/Seeding/DefaultListsSeeder.cs
new file mode 100644
index 0000000..e3ec03d
--- /dev/null
+++ b/src/ClaudeDo.Data/Seeding/DefaultListsSeeder.cs
@@ -0,0 +1,25 @@
+using ClaudeDo.Data.Models;
+using Microsoft.EntityFrameworkCore;
+
+namespace ClaudeDo.Data.Seeding;
+
+public static class DefaultListsSeeder
+{
+    private static readonly string[] Defaults = { "My Day", "Important", "Planned" };
+
+    public static async Task SeedAsync(ClaudeDoDbContext ctx, CancellationToken ct = default)
+    {
+        var existing = await ctx.Lists.Select(l => l.Name).ToListAsync(ct);
+        var now = DateTime.UtcNow;
+        foreach (var name in Defaults.Where(n => !existing.Contains(n)))
+        {
+            ctx.Lists.Add(new ListEntity
+            {
+                Id = Guid.NewGuid().ToString("N"),
+                Name = name,
+                CreatedAt = now,
+            });
+        }
+        await ctx.SaveChangesAsync(ct);
+    }
+}
diff --git a/src/ClaudeDo.Installer/Steps/InitDatabaseStep.cs b/src/ClaudeDo.Installer/Steps/InitDatabaseStep.cs
index 007b36c..3630996 100644
--- a/src/ClaudeDo.Installer/Steps/InitDatabaseStep.cs
+++ b/src/ClaudeDo.Installer/Steps/InitDatabaseStep.cs
@@ -1,4 +1,5 @@
 using ClaudeDo.Data;
+using ClaudeDo.Data.Seeding;
 using ClaudeDo.Installer.Core;
 using Microsoft.EntityFrameworkCore;
 
@@ -20,6 +21,7 @@ public sealed class InitDatabaseStep : IInstallStep
                 .Options;
             using var context = new ClaudeDoDbContext(options);
             ClaudeDoDbContext.MigrateAndConfigure(context);
+            DefaultListsSeeder.SeedAsync(context).GetAwaiter().GetResult();
 
             progress.Report("Schema applied successfully");
             return Task.FromResult(StepResult.Ok());
diff --git a/tests/ClaudeDo.Worker.Tests/UiSchema/DefaultListSeedTests.cs b/tests/ClaudeDo.Worker.Tests/UiSchema/DefaultListSeedTests.cs
new file mode 100644
index 0000000..2c610c5
--- /dev/null
+++ b/tests/ClaudeDo.Worker.Tests/UiSchema/DefaultListSeedTests.cs
@@ -0,0 +1,41 @@
+using ClaudeDo.Data;
+using ClaudeDo.Data.Seeding;
+using Microsoft.EntityFrameworkCore;
+using Xunit;
+
+namespace ClaudeDo.Worker.Tests.UiSchema;
+
+public class DefaultListSeedTests : IDisposable
+{
+    private readonly string _dbPath = Path.Combine(Path.GetTempPath(), $"claudedo-seed-{Guid.NewGuid():N}.db");
+
+    private ClaudeDoDbContext NewContext()
+    {
+        var opts = new DbContextOptionsBuilder<ClaudeDoDbContext>()
+            .UseSqlite($"Data Source={_dbPath}").Options;
+        var ctx = new ClaudeDoDbContext(opts);
+        ctx.Database.EnsureCreated();
+        return ctx;
+    }
+
+    [Fact]
+    public async Task Seeds_MyDay_Important_Planned_Lists_Idempotently()
+    {
+        await using (var ctx = NewContext())
+        {
+            await DefaultListsSeeder.SeedAsync(ctx);
+            await DefaultListsSeeder.SeedAsync(ctx); // idempotent
+        }
+
+        await using var verify = NewContext();
+        var names = verify.Lists.Select(l => l.Name).OrderBy(n => n).ToList();
+        Assert.Equal(new[] { "Important", "My Day", "Planned" }, names);
+    }
+
+    public void Dispose()
+    {
+        try { if (File.Exists(_dbPath)) File.Delete(_dbPath); } catch { }
+        try { if (File.Exists(_dbPath + "-wal")) File.Delete(_dbPath + "-wal"); } catch { }
+        try { if (File.Exists(_dbPath + "-shm")) File.Delete(_dbPath + "-shm"); } catch { }
+    }
+}