diff --git a/pkg/cmd/build.go b/pkg/cmd/build.go
index d6d5722..52cfb13 100644
--- a/pkg/cmd/build.go
+++ b/pkg/cmd/build.go
@@ -5,10 +5,12 @@ import (
 	"bytes"
 	"compress/gzip"
 	"context"
+	"encoding/hex"
 	"fmt"
 	"io"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"github.com/kernel/hypeman-go"
 	"github.com/kernel/hypeman-go/option"
@@ -19,9 +21,9 @@ import (
 var buildCmd = cli.Command{
 	Name:      "build",
 	Aliases:   []string{"builds"},
-	Usage:     "Build an image from a Dockerfile",
+	Usage:     "Build an image from a Dockerfile or native macOS recipe",
 	ArgsUsage: "[path]",
-	Description: `Build an image from a Dockerfile and source context.
+	Description: `Build an image from a Dockerfile or native macOS recipe and source context.
 
 The path argument specifies the build context directory containing the
 source code and Dockerfile. If not specified, the current directory is used.
@@ -42,7 +44,11 @@ Examples:
   hypeman build -f Dockerfile.prod ./myapp
 
   # Build with custom timeout
-  hypeman build --timeout 1200 ./myapp`,
+  hypeman build --timeout 1200 ./myapp
+
+  # Build from hypeman-macos-build.json using an installed, digest-pinned base
+  hypeman build --machine-base-image registry.example/macos/base@sha256:<digest> ./macos`,
+
 	Flags: []cli.Flag{
 		&cli.StringFlag{
 			Name:    "file",
@@ -58,6 +64,14 @@ Examples:
 			Name:  "base-image-digest",
 			Usage: "Pinned base image digest for reproducible builds",
 		},
+		&cli.StringFlag{
+			Name:  "machine-base-image",
+			Usage: "Digest-pinned machine base image for a native macOS build",
+		},
+		&cli.StringFlag{
+			Name:  "machine-network-mode",
+			Usage: "Native macOS build networking: isolated (default) or unrestricted NAT egress",
+		},
 		&cli.StringFlag{
 			Name:    "builder",
 			Aliases: []string{"builder-id"},
@@ -162,37 +176,83 @@ func handleBuild(ctx context.Context, cmd *cli.Command) error {
 		opts = append(opts, debugMiddlewareOption)
 	}
 
-	// Build params
-	params := hypeman.BuildNewParams{
-		Source:         bytes.NewReader(tarball.Bytes()),
-		TimeoutSeconds: hypeman.Opt(int64(timeout)),
+	params, err := buildNewParams(cmd, tarball.Bytes(), dockerfileContent, timeout)
+	if err != nil {
+		return err
 	}
 
-	if dockerfileContent != "" {
-		params.Dockerfile = hypeman.Opt(dockerfileContent)
+	// Start build
+	build, err := client.Builds.New(ctx, params, opts...)
+	if err != nil {
+		return fmt.Errorf("failed to start build: %w", err)
 	}
 
-	if v := cmd.String("base-image-digest"); v != "" {
-		params.BaseImageDigest = hypeman.Opt(v)
-	}
-	if v := cmd.String("builder"); v != "" {
-		params.BuilderID = hypeman.Opt(v)
-	}
-	if v := cmd.String("cache-scope"); v != "" {
-		params.CacheScope = hypeman.Opt(v)
-	}
-	if v := cmd.String("global-cache-key"); v != "" {
-		params.GlobalCacheKey = hypeman.Opt(v)
-	}
-	if v := cmd.String("is-admin-build"); v != "" {
-		params.IsAdminBuild = hypeman.Opt(v)
+	fmt.Fprintf(os.Stderr, "Build started: %s\n", build.ID)
+
+	// Stream build events
+	err = streamBuildEventsSDK(ctx, client, build.ID, opts)
+	if err != nil {
+		return fmt.Errorf("build failed: %w", err)
 	}
-	if v := cmd.String("secrets"); v != "" {
-		params.Secrets = hypeman.Opt(v)
+
+	return nil
+}
+
+func buildNewParams(cmd *cli.Command, source []byte, dockerfile string, timeout int) (hypeman.BuildNewParams, error) {
+	params := hypeman.BuildNewParams{
+		Source:         bytes.NewReader(source),
+		TimeoutSeconds: hypeman.Opt(int64(timeout)),
 	}
-	if v := cmd.String("image-name"); v != "" {
-		params.ImageName = hypeman.Opt(v)
+
+	machineBaseImage := cmd.String("machine-base-image")
+	if machineBaseImage != "" {
+		if err := validateMachineBaseImage(machineBaseImage); err != nil {
+			return params, err
+		}
+		for _, flag := range []string{"file", "base-image-digest", "builder", "cache-scope", "global-cache-key", "is-admin-build", "secrets", "image-name"} {
+			if cmd.IsSet(flag) {
+				return params, fmt.Errorf("--%s cannot be used with --machine-base-image", flag)
+			}
+		}
+		extra := map[string]any{"machine_base_image": machineBaseImage}
+		if cmd.IsSet("machine-network-mode") {
+			mode := cmd.String("machine-network-mode")
+			if mode != "isolated" && mode != "egress" {
+				return params, fmt.Errorf("--machine-network-mode must be isolated or egress")
+			}
+			extra["machine_network_mode"] = mode
+		}
+		params.SetExtraFields(extra)
+	} else {
+		if cmd.IsSet("machine-network-mode") {
+			return params, fmt.Errorf("--machine-network-mode requires --machine-base-image")
+		}
+		if dockerfile != "" {
+			params.Dockerfile = hypeman.Opt(dockerfile)
+		}
+		if v := cmd.String("base-image-digest"); v != "" {
+			params.BaseImageDigest = hypeman.Opt(v)
+		}
+		if v := cmd.String("builder"); v != "" {
+			params.BuilderID = hypeman.Opt(v)
+		}
+		if v := cmd.String("cache-scope"); v != "" {
+			params.CacheScope = hypeman.Opt(v)
+		}
+		if v := cmd.String("global-cache-key"); v != "" {
+			params.GlobalCacheKey = hypeman.Opt(v)
+		}
+		if v := cmd.String("is-admin-build"); v != "" {
+			params.IsAdminBuild = hypeman.Opt(v)
+		}
+		if v := cmd.String("secrets"); v != "" {
+			params.Secrets = hypeman.Opt(v)
+		}
+		if v := cmd.String("image-name"); v != "" {
+			params.ImageName = hypeman.Opt(v)
+		}
 	}
+
 	if cmd.IsSet("cpus") {
 		params.CPUs = hypeman.Opt(int64(cmd.Int("cpus")))
 	}
@@ -206,25 +266,21 @@ func handleBuild(ctx context.Context, cmd *cli.Command) error {
 	if len(tags) > 0 {
 		tagsJSON, err := marshalStringMap(tags)
 		if err != nil {
-			return fmt.Errorf("failed to encode tags: %w", err)
+			return params, fmt.Errorf("failed to encode tags: %w", err)
 		}
 		params.Tags = hypeman.Opt(tagsJSON)
 	}
+	return params, nil
+}
 
-	// Start build
-	build, err := client.Builds.New(ctx, params, opts...)
-	if err != nil {
-		return fmt.Errorf("failed to start build: %w", err)
+func validateMachineBaseImage(image string) error {
+	repository, digest, ok := strings.Cut(image, "@sha256:")
+	if !ok || repository == "" || strings.ContainsAny(repository, "@ \t\r\n") || len(digest) != 64 || digest != strings.ToLower(digest) {
+		return fmt.Errorf("--machine-base-image must be pinned by a sha256 digest")
 	}
-
-	fmt.Fprintf(os.Stderr, "Build started: %s\n", build.ID)
-
-	// Stream build events
-	err = streamBuildEventsSDK(ctx, client, build.ID, opts)
-	if err != nil {
-		return fmt.Errorf("build failed: %w", err)
+	if _, err := hex.DecodeString(digest); err != nil {
+		return fmt.Errorf("--machine-base-image must be pinned by a sha256 digest")
 	}
-
 	return nil
 }
 
diff --git a/pkg/cmd/build_test.go b/pkg/cmd/build_test.go
new file mode 100644
index 0000000..c532b73
--- /dev/null
+++ b/pkg/cmd/build_test.go
@@ -0,0 +1,132 @@
+package cmd
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"mime"
+	"mime/multipart"
+	"sort"
+	"strings"
+	"testing"
+
+	"github.com/kernel/hypeman-go"
+	"github.com/stretchr/testify/require"
+	"github.com/urfave/cli/v3"
+)
+
+const testMachineBaseImage = "registry.example.com/macos/base@sha256:" + "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"
+
+func parseBuildParams(t *testing.T, args ...string) (hypeman.BuildNewParams, error) {
+	t.Helper()
+	var params hypeman.BuildNewParams
+	command := &cli.Command{
+		Name:  "build",
+		Flags: testBuildFlags(),
+		Action: func(_ context.Context, cmd *cli.Command) error {
+			var err error
+			params, err = buildNewParams(cmd, []byte("source archive"), "", cmd.Int("timeout"))
+			return err
+		},
+	}
+	argv := append([]string{"build"}, args...)
+	return params, command.Run(context.Background(), argv)
+}
+
+func testBuildFlags() []cli.Flag {
+	return []cli.Flag{
+		&cli.StringFlag{Name: "file", Aliases: []string{"f"}},
+		&cli.IntFlag{Name: "timeout", Value: 600},
+		&cli.StringFlag{Name: "base-image-digest"},
+		&cli.StringFlag{Name: "machine-base-image"},
+		&cli.StringFlag{Name: "machine-network-mode"},
+		&cli.StringFlag{Name: "builder", Aliases: []string{"builder-id"}},
+		&cli.StringFlag{Name: "cache-scope"},
+		&cli.StringFlag{Name: "global-cache-key"},
+		&cli.StringFlag{Name: "is-admin-build"},
+		&cli.StringFlag{Name: "secrets"},
+		&cli.StringFlag{Name: "image-name"},
+		&cli.IntFlag{Name: "cpus"},
+		&cli.IntFlag{Name: "memory"},
+		&cli.StringSliceFlag{Name: "tag"},
+	}
+}
+
+func multipartFieldNames(t *testing.T, params hypeman.BuildNewParams) []string {
+	t.Helper()
+	body, contentType, err := params.MarshalMultipart()
+	require.NoError(t, err)
+	_, parameter, err := mime.ParseMediaType(contentType)
+	require.NoError(t, err)
+	reader := multipart.NewReader(bytes.NewReader(body), parameter["boundary"])
+	var names []string
+	for {
+		part, err := reader.NextPart()
+		if err == io.EOF {
+			break
+		}
+		require.NoError(t, err)
+		names = append(names, part.FormName())
+		_ = part.Close()
+	}
+	sort.Strings(names)
+	return names
+}
+
+func TestMachineBuildMultipartFields(t *testing.T) {
+	params, err := parseBuildParams(t,
+		"--machine-base-image", testMachineBaseImage,
+		"--cpus", "4", "--memory", "8192", "--tag", "team=cli")
+	require.NoError(t, err)
+
+	got := multipartFieldNames(t, params)
+	want := []string{"cpus", "machine_base_image", "memory_mb", "source", "tags", "timeout_seconds"}
+	require.Equal(t, want, got)
+}
+
+func TestMachineBuildNetworkSelection(t *testing.T) {
+	params, err := parseBuildParams(t, "--machine-base-image", testMachineBaseImage, "--machine-network-mode", "egress")
+	require.NoError(t, err)
+	require.Equal(t, []string{"machine_base_image", "machine_network_mode", "source", "timeout_seconds"}, multipartFieldNames(t, params))
+	_, err = parseBuildParams(t, "--machine-base-image", testMachineBaseImage, "--machine-network-mode", "bridge")
+	require.ErrorContains(t, err, "must be isolated or egress")
+	_, err = parseBuildParams(t, "--machine-network-mode", "egress")
+	require.ErrorContains(t, err, "requires --machine-base-image")
+}
+
+func TestMachineBuildRejectsLinuxOptions(t *testing.T) {
+	for _, option := range []string{
+		"--file", "--base-image-digest", "--builder", "--cache-scope",
+		"--global-cache-key", "--is-admin-build", "--secrets", "--image-name",
+	} {
+		t.Run(strings.TrimLeft(option, "-"), func(t *testing.T) {
+			value := "value"
+			if option == "--file" {
+				value = "Dockerfile"
+			}
+			args := []string{"--machine-base-image", testMachineBaseImage, option, value}
+			_, err := parseBuildParams(t, args...)
+			require.ErrorContains(t, err, option+" cannot be used with --machine-base-image")
+		})
+	}
+}
+
+func TestMachineBuildRequiresDigestPinnedImage(t *testing.T) {
+	for _, image := range []string{
+		"registry.example.com/macos/base:latest", "registry.example.com/macos/base@sha256:abc",
+		"@sha256:" + strings.Repeat("a", 64),
+		"registry.example.com/macos/base@sha256:" + strings.Repeat("A", 64),
+		"registry.example.com/macos/base@extra@sha256:" + strings.Repeat("a", 64),
+	} {
+		_, err := parseBuildParams(t, "--machine-base-image", image)
+		require.ErrorContains(t, err, "must be pinned by a sha256 digest")
+	}
+}
+
+func TestLinuxBuildMultipartFieldsRemainUnchanged(t *testing.T) {
+	params, err := parseBuildParams(t, "--base-image-digest", "sha256:base")
+	require.NoError(t, err)
+	got := multipartFieldNames(t, params)
+	want := []string{"base_image_digest", "source", "timeout_seconds"}
+	require.Equal(t, want, got)
+}