diff --git a/internal/servicedef/servicedef.go b/internal/servicedef/servicedef.go
index 7135218..fae858d 100644
--- a/internal/servicedef/servicedef.go
+++ b/internal/servicedef/servicedef.go
@@ -16,8 +16,10 @@ import (
 // ServiceDef is the top-level TOML structure for a service definition file.
 type ServiceDef struct {
 	Name       string         `toml:"name"`
-	Node       string         `toml:"node"`
+	Node       string         `toml:"node,omitempty"`
+	Tier       string         `toml:"tier,omitempty"`
 	Active     *bool          `toml:"active,omitempty"`
+	Comment    string         `toml:"comment,omitempty"`
 	Path       string         `toml:"path,omitempty"`
 	Build      *BuildDef      `toml:"build,omitempty"`
 	Components []ComponentDef `toml:"components"`
@@ -36,6 +38,7 @@ type RouteDef struct {
 	Port     int    `toml:"port"`
 	Mode     string `toml:"mode,omitempty"`
 	Hostname string `toml:"hostname,omitempty"`
+	Public   bool   `toml:"public,omitempty"`
 }
 
 // ComponentDef describes a single container component within a service.
@@ -129,8 +132,9 @@ func validate(def *ServiceDef) error {
 	if def.Name == "" {
 		return fmt.Errorf("service name is required")
 	}
-	if def.Node == "" {
-		return fmt.Errorf("service node is required")
+	// v2: either node or tier must be set. Tier defaults to "worker" if both empty.
+	if def.Node == "" && def.Tier == "" {
+		def.Tier = "worker"
 	}
 	if len(def.Components) == 0 {
 		return fmt.Errorf("service %q must have at least one component", def.Name)
@@ -191,8 +195,11 @@ func validateRoutes(compName, svcName string, routes []RouteDef) error {
 // ToProto converts a ServiceDef to a proto ServiceSpec.
 func ToProto(def *ServiceDef) *mcpv1.ServiceSpec {
 	spec := &mcpv1.ServiceSpec{
-		Name:   def.Name,
-		Active: def.Active != nil && *def.Active,
+		Name:    def.Name,
+		Active:  def.Active != nil && *def.Active,
+		Comment: def.Comment,
+		Tier:    def.Tier,
+		Node:    def.Node,
 	}
 
 	for _, c := range def.Components {
@@ -213,6 +220,7 @@ func ToProto(def *ServiceDef) *mcpv1.ServiceSpec {
 				Port:     int32(r.Port), //nolint:gosec // port range validated
 				Mode:     r.Mode,
 				Hostname: r.Hostname,
+				Public:   r.Public,
 			})
 		}
 		spec.Components = append(spec.Components, cs)
@@ -227,9 +235,11 @@ func ToProto(def *ServiceDef) *mcpv1.ServiceSpec {
 func FromProto(spec *mcpv1.ServiceSpec, node string) *ServiceDef {
 	active := spec.GetActive()
 	def := &ServiceDef{
-		Name:   spec.GetName(),
-		Node:   node,
-		Active: &active,
+		Name:    spec.GetName(),
+		Node:    node,
+		Tier:    spec.GetTier(),
+		Active:  &active,
+		Comment: spec.GetComment(),
 	}
 
 	for _, c := range spec.GetComponents() {
@@ -250,6 +260,7 @@ func FromProto(spec *mcpv1.ServiceSpec, node string) *ServiceDef {
 				Port:     int(r.GetPort()),
 				Mode:     r.GetMode(),
 				Hostname: r.GetHostname(),
+				Public:   r.GetPublic(),
 			})
 		}
 		def.Components = append(def.Components, cd)
diff --git a/internal/servicedef/servicedef_test.go b/internal/servicedef/servicedef_test.go
index bfe3a6b..f33c25b 100644
--- a/internal/servicedef/servicedef_test.go
+++ b/internal/servicedef/servicedef_test.go
@@ -119,14 +119,8 @@ func TestValidation(t *testing.T) {
 			},
 			wantErr: "service name is required",
 		},
-		{
-			name: "missing node",
-			def: &ServiceDef{
-				Name:       "svc",
-				Components: []ComponentDef{{Name: "api", Image: "img:v1"}},
-			},
-			wantErr: "service node is required",
-		},
+		// v2: missing node no longer errors — defaults to tier=worker.
+		// Tested separately in TestValidationNodeTierDefault.
 		{
 			name: "empty components",
 			def: &ServiceDef{