feat: wire up extra_packages config to Docker image build

assets/Dockerfile

@@ -19,6 +19,12 @@ RUN apt-get update && apt-get install -y \
     && apt-get install -y nodejs \
     && rm -rf /var/lib/apt/lists/*
 
+ARG EXTRA_PACKAGES=""
+RUN if [ -n "$EXTRA_PACKAGES" ]; then \
+    apt-get update && apt-get install -y $EXTRA_PACKAGES \
+    && rm -rf /var/lib/apt/lists/*; \
+    fi
+
 RUN npm install -g @anthropic-ai/claude-code
 
 RUN userdel -r ubuntu 2>/dev/null; useradd -m -s /bin/bash -u 1000 agent

internal/daemon/daemon.go

@@ -311,7 +311,7 @@ func Run(projectDir string, cfg *config.Config, apiKey, oauthToken string, docke
 
 	// Build image.
 	slog.Info("building docker image")
-	if err := d.docker.BuildImage(projectDir); err != nil {
+	if err := d.docker.BuildImage(projectDir, cfg.Docker.ExtraPackages); err != nil {
 		return fmt.Errorf("daemon: failed to build image: %w", err)
 	}
 

internal/daemon/daemon_test.go

@@ -32,7 +32,7 @@ type mockDockerClient struct {
 	logsErr     error
 }
 
-func (m *mockDockerClient) BuildImage(projectDir string) error {
+func (m *mockDockerClient) BuildImage(projectDir string, extraPackages []string) error {
 	return m.buildErr
 }
 

internal/docker/docker.go

@@ -62,7 +62,7 @@ type AgentInfo struct {
 // DockerClient is the interface for Docker operations so the daemon and CLI
 // can be tested without a real Docker daemon.
 type DockerClient interface {
-	BuildImage(projectDir string) error
+	BuildImage(projectDir string, extraPackages []string) error
 	StartAgent(ctx context.Context, opts AgentOpts) (string, error)
 	StopAgent(ctx context.Context, agentID int) error
 	StopAllAgents(ctx context.Context) error
@@ -113,7 +113,7 @@ func newClientWithAPI(projectName string, api dockerAPI) *Client {
 
 // BuildImage writes the embedded Dockerfile and entrypoint into .metamorph/docker/,
 // creates a tar build context, and builds the image.
-func (c *Client) BuildImage(projectDir string) error {
+func (c *Client) BuildImage(projectDir string, extraPackages []string) error {
 	buildDir := filepath.Join(projectDir, constants.DockerDir)
 	if err := os.MkdirAll(buildDir, 0755); err != nil {
 		return fmt.Errorf("docker: failed to create build dir: %w", err)
@@ -137,13 +137,20 @@ func (c *Client) BuildImage(projectDir string) error {
 		return fmt.Errorf("docker: failed to create build context: %w", err)
 	}
 
+	buildArgs := make(map[string]*string)
+	if len(extraPackages) > 0 {
+		pkgs := strings.Join(extraPackages, " ")
+		buildArgs["EXTRA_PACKAGES"] = &pkgs
+	}
+
 	ctx, cancel := context.WithTimeout(context.Background(), buildTimeout)
 	defer cancel()
 
 	resp, err := c.cli.ImageBuild(ctx, buildCtx, types.ImageBuildOptions{
 		Tags:       []string{defaultImageTag},
 		Dockerfile: "Dockerfile",
 		Remove:     true,
+		BuildArgs:  buildArgs,
 	})
 	if err != nil {
 		return fmt.Errorf("docker: failed to build image: %w", err)

internal/docker/docker_test.go

@@ -51,10 +51,11 @@ type mockDocker struct {
 	logsErr     error
 
 	// Track calls for assertions.
-	created []mockCreateCall
-	started []string
-	stopped []string
-	removed []string
+	buildOptions types.ImageBuildOptions
+	created      []mockCreateCall
+	started      []string
+	stopped      []string
+	removed      []string
 }
 
 type mockCreateCall struct {
@@ -68,6 +69,7 @@ func (m *mockDocker) Ping(ctx context.Context) (types.Ping, error) {
 }
 
 func (m *mockDocker) ImageBuild(ctx context.Context, buildContext io.Reader, options types.ImageBuildOptions) (types.ImageBuildResponse, error) {
+	m.buildOptions = options
 	if m.buildErr != nil {
 		return types.ImageBuildResponse{}, m.buildErr
 	}
@@ -121,7 +123,7 @@ func TestBuildImage(t *testing.T) {
 		mock := &mockDocker{buildBody: `{"stream":"Successfully built abc123"}`}
 		c := newClientWithAPI("test-project", mock)
 
-		if err := c.BuildImage(projectDir); err != nil {
+		if err := c.BuildImage(projectDir, nil); err != nil {
 			t.Fatalf("BuildImage: %v", err)
 		}
 
@@ -145,14 +147,48 @@ func TestBuildImage(t *testing.T) {
 		mock := &mockDocker{buildErr: fmt.Errorf("build failed")}
 		c := newClientWithAPI("test-project", mock)
 
-		err := c.BuildImage(projectDir)
+		err := c.BuildImage(projectDir, nil)
 		if err == nil {
 			t.Fatal("expected error")
 		}
 		if !strings.Contains(err.Error(), "failed to build image") {
 			t.Errorf("unexpected error: %v", err)
 		}
 	})
+
+	t.Run("passes extra packages as build arg", func(t *testing.T) {
+		projectDir := t.TempDir()
+
+		mock := &mockDocker{buildBody: `{"stream":"Successfully built abc123"}`}
+		c := newClientWithAPI("test-project", mock)
+
+		if err := c.BuildImage(projectDir, []string{"vim", "htop"}); err != nil {
+			t.Fatalf("BuildImage: %v", err)
+		}
+
+		got, ok := mock.buildOptions.BuildArgs["EXTRA_PACKAGES"]
+		if !ok || got == nil {
+			t.Fatal("expected EXTRA_PACKAGES build arg to be set")
+		}
+		if *got != "vim htop" {
+			t.Errorf("EXTRA_PACKAGES = %q, want %q", *got, "vim htop")
+		}
+	})
+
+	t.Run("omits build arg when no extra packages", func(t *testing.T) {
+		projectDir := t.TempDir()
+
+		mock := &mockDocker{buildBody: `{"stream":"Successfully built abc123"}`}
+		c := newClientWithAPI("test-project", mock)
+
+		if err := c.BuildImage(projectDir, nil); err != nil {
+			t.Fatalf("BuildImage: %v", err)
+		}
+
+		if _, ok := mock.buildOptions.BuildArgs["EXTRA_PACKAGES"]; ok {
+			t.Error("EXTRA_PACKAGES build arg should not be set when no extra packages")
+		}
+	})
 }
 
 func TestStartAgent(t *testing.T) {
@@ -716,7 +752,7 @@ func TestDockerClientInterface(t *testing.T) {
 // mockDockerClient is a full mock of the DockerClient interface for consumers.
 type mockDockerClient struct{}
 
-func (m *mockDockerClient) BuildImage(projectDir string) error { return nil }
+func (m *mockDockerClient) BuildImage(projectDir string, extraPackages []string) error { return nil }
 func (m *mockDockerClient) StartAgent(ctx context.Context, opts AgentOpts) (string, error) {
 	return "mock-id", nil
 }