diff --git a/src/ClaudeDo.Worker/Services/DefaultAgentSeeder.cs b/src/ClaudeDo.Worker/Services/DefaultAgentSeeder.cs
new file mode 100644
index 0000000..895197b
--- /dev/null
+++ b/src/ClaudeDo.Worker/Services/DefaultAgentSeeder.cs
@@ -0,0 +1,60 @@
+using Microsoft.Extensions.Logging;
+
+namespace ClaudeDo.Worker.Services;
+
+public sealed record SeedResult(int Copied, int Skipped);
+
+public sealed class DefaultAgentSeeder
+{
+    private readonly string _bundleDir;
+    private readonly string _targetDir;
+    private readonly ILogger<DefaultAgentSeeder>? _logger;
+
+    public DefaultAgentSeeder(string bundleDir, string targetDir, ILogger<DefaultAgentSeeder>? logger = null)
+    {
+        _bundleDir = bundleDir;
+        _targetDir = targetDir;
+        _logger = logger;
+    }
+
+    public async Task<SeedResult> SeedMissingAsync(CancellationToken ct = default)
+    {
+        if (!Directory.Exists(_bundleDir))
+        {
+            _logger?.LogWarning("DefaultAgents bundle dir not found: {Dir}", _bundleDir);
+            return new SeedResult(0, 0);
+        }
+
+        Directory.CreateDirectory(_targetDir);
+
+        int copied = 0;
+        int skipped = 0;
+
+        foreach (var src in Directory.EnumerateFiles(_bundleDir, "*.md"))
+        {
+            ct.ThrowIfCancellationRequested();
+            var fileName = Path.GetFileName(src);
+            var dst = Path.Combine(_targetDir, fileName);
+
+            if (File.Exists(dst))
+            {
+                skipped++;
+                continue;
+            }
+
+            try
+            {
+                using var input = File.OpenRead(src);
+                using var output = File.Create(dst);
+                await input.CopyToAsync(output, ct);
+                copied++;
+            }
+            catch (Exception ex)
+            {
+                _logger?.LogWarning(ex, "Failed to copy default agent {File}", fileName);
+            }
+        }
+
+        return new SeedResult(copied, skipped);
+    }
+}
diff --git a/tests/ClaudeDo.Worker.Tests/Services/DefaultAgentSeederTests.cs b/tests/ClaudeDo.Worker.Tests/Services/DefaultAgentSeederTests.cs
new file mode 100644
index 0000000..a5b53b6
--- /dev/null
+++ b/tests/ClaudeDo.Worker.Tests/Services/DefaultAgentSeederTests.cs
@@ -0,0 +1,112 @@
+using ClaudeDo.Worker.Services;
+
+namespace ClaudeDo.Worker.Tests.Services;
+
+public sealed class DefaultAgentSeederTests : IDisposable
+{
+    private readonly string _bundleDir;
+    private readonly string _targetDir;
+
+    public DefaultAgentSeederTests()
+    {
+        var root = Path.Combine(Path.GetTempPath(), $"claudedo_seeder_{Guid.NewGuid():N}");
+        _bundleDir = Path.Combine(root, "bundle");
+        _targetDir = Path.Combine(root, "target");
+        Directory.CreateDirectory(_bundleDir);
+        Directory.CreateDirectory(_targetDir);
+    }
+
+    public void Dispose()
+    {
+        try { Directory.Delete(Path.GetDirectoryName(_bundleDir)!, true); } catch { }
+    }
+
+    private async Task WriteBundleAsync(string name, string content)
+    {
+        await File.WriteAllTextAsync(Path.Combine(_bundleDir, name), content);
+    }
+
+    [Fact]
+    public async Task SeedMissing_CopiesAllFiles_WhenTargetEmpty()
+    {
+        await WriteBundleAsync("a.md", "A");
+        await WriteBundleAsync("b.md", "B");
+        var seeder = new DefaultAgentSeeder(_bundleDir, _targetDir);
+
+        var result = await seeder.SeedMissingAsync();
+
+        Assert.Equal(2, result.Copied);
+        Assert.Equal(0, result.Skipped);
+        Assert.True(File.Exists(Path.Combine(_targetDir, "a.md")));
+        Assert.True(File.Exists(Path.Combine(_targetDir, "b.md")));
+    }
+
+    [Fact]
+    public async Task SeedMissing_SkipsExistingFiles()
+    {
+        await WriteBundleAsync("a.md", "bundled");
+        await File.WriteAllTextAsync(Path.Combine(_targetDir, "a.md"), "user-modified");
+        var seeder = new DefaultAgentSeeder(_bundleDir, _targetDir);
+
+        var result = await seeder.SeedMissingAsync();
+
+        Assert.Equal(0, result.Copied);
+        Assert.Equal(1, result.Skipped);
+        var content = await File.ReadAllTextAsync(Path.Combine(_targetDir, "a.md"));
+        Assert.Equal("user-modified", content);
+    }
+
+    [Fact]
+    public async Task SeedMissing_MixedState_CopiesOnlyMissing()
+    {
+        await WriteBundleAsync("a.md", "A");
+        await WriteBundleAsync("b.md", "B");
+        await File.WriteAllTextAsync(Path.Combine(_targetDir, "a.md"), "existing");
+        var seeder = new DefaultAgentSeeder(_bundleDir, _targetDir);
+
+        var result = await seeder.SeedMissingAsync();
+
+        Assert.Equal(1, result.Copied);
+        Assert.Equal(1, result.Skipped);
+        Assert.Equal("existing", await File.ReadAllTextAsync(Path.Combine(_targetDir, "a.md")));
+        Assert.Equal("B", await File.ReadAllTextAsync(Path.Combine(_targetDir, "b.md")));
+    }
+
+    [Fact]
+    public async Task SeedMissing_ReturnsZero_WhenBundleDirMissing()
+    {
+        var missingBundle = Path.Combine(Path.GetTempPath(), $"claudedo_missing_{Guid.NewGuid():N}");
+        var seeder = new DefaultAgentSeeder(missingBundle, _targetDir);
+
+        var result = await seeder.SeedMissingAsync();
+
+        Assert.Equal(0, result.Copied);
+        Assert.Equal(0, result.Skipped);
+    }
+
+    [Fact]
+    public async Task SeedMissing_CreatesTargetDir_IfMissing()
+    {
+        await WriteBundleAsync("a.md", "A");
+        var missingTarget = Path.Combine(_targetDir, "nested", "created");
+        var seeder = new DefaultAgentSeeder(_bundleDir, missingTarget);
+
+        var result = await seeder.SeedMissingAsync();
+
+        Assert.Equal(1, result.Copied);
+        Assert.True(File.Exists(Path.Combine(missingTarget, "a.md")));
+    }
+
+    [Fact]
+    public async Task SeedMissing_IgnoresNonMarkdownFiles()
+    {
+        await WriteBundleAsync("a.md", "A");
+        await File.WriteAllTextAsync(Path.Combine(_bundleDir, "readme.txt"), "not an agent");
+        var seeder = new DefaultAgentSeeder(_bundleDir, _targetDir);
+
+        var result = await seeder.SeedMissingAsync();
+
+        Assert.Equal(1, result.Copied);
+        Assert.False(File.Exists(Path.Combine(_targetDir, "readme.txt")));
+    }
+}