diff --git a/backends/aggregate.go b/backends/aggregate.go
index a836e235d6..158229869b 100644
--- a/backends/aggregate.go
+++ b/backends/aggregate.go
@@ -11,22 +11,21 @@ import (
 
 func Aggregate() beam.Sender {
 	backend := beam.NewServer()
-	backend.OnVerb(beam.Spawn, beam.Handler(func(ctx *beam.Message) error {
+	backend.OnSpawn(func(cmd ...string) (beam.Sender, error) {
 		allBackends := New()
 		instance := beam.NewServer()
 
-		a, err := newAggregator(allBackends, instance, ctx.Args)
+		a, err := newAggregator(allBackends, instance, cmd)
 		if err != nil {
-			return err
+			return nil, err
 		}
 
-		instance.OnVerb(beam.Attach, beam.Handler(a.attach))
-		instance.OnVerb(beam.Start, beam.Handler(a.start))
-		instance.OnVerb(beam.Ls, beam.Handler(a.ls))
+		instance.OnAttach(a.attach)
+		instance.OnStart(a.start)
+		instance.OnLs(a.ls)
 
-		_, err = ctx.Ret.Send(&beam.Message{Verb: beam.Ack, Ret: instance})
-		return err
-	}))
+		return instance, nil
+	})
 	return backend
 }
 
@@ -61,13 +60,13 @@ func newAggregator(allBackends *beam.Object, server *beam.Server, args []string)
 	return a, nil
 }
 
-func (a *aggregator) attach(ctx *beam.Message) error {
-	if ctx.Args[0] != "" {
+func (a *aggregator) attach(name string, ret beam.Sender) error {
+	if name != "" {
 		// TODO: implement this?
 		return fmt.Errorf("attaching to a child is not implemented")
 	}
 
-	if _, err := ctx.Ret.Send(&beam.Message{Verb: beam.Ack, Ret: a.server}); err != nil {
+	if _, err := ret.Send(&beam.Message{Verb: beam.Ack, Ret: a.server}); err != nil {
 		return err
 	}
 
@@ -81,7 +80,7 @@ func (a *aggregator) attach(ctx *beam.Message) error {
 		copies.Add(1)
 		go func() {
 			log.Printf("copying output from %#v\n", b)
-			beam.Copy(ctx.Ret, r)
+			beam.Copy(ret, r)
 			log.Printf("finished output from %#v\n", b)
 			copies.Done()
 		}()
@@ -91,29 +90,26 @@ func (a *aggregator) attach(ctx *beam.Message) error {
 	return nil
 }
 
-func (a *aggregator) start(ctx *beam.Message) error {
+func (a *aggregator) start() error {
 	for _, b := range a.backends {
 		err := b.Start()
 		if err != nil {
 			return err
 		}
 	}
-	_, err := ctx.Ret.Send(&beam.Message{Verb: beam.Ack})
-	return err
+	return nil
 }
 
-func (a *aggregator) ls(ctx *beam.Message) error {
+func (a *aggregator) ls() ([]string, error) {
 	var children []string
 
 	for _, b := range a.backends {
 		bChildren, err := b.Ls()
 		if err != nil {
-			return err
+			return nil, err
 		}
 		children = append(children, bChildren...)
 	}
 
-	ctx.Ret.Send(&beam.Message{Verb: beam.Set, Args: children})
-
-	return nil
+	return children, nil
 }
diff --git a/backends/orchard.go b/backends/orchard.go
index 3425c1e8bd..f16d5aebf3 100644
--- a/backends/orchard.go
+++ b/backends/orchard.go
@@ -13,11 +13,11 @@ import (
 
 func Orchard() beam.Sender {
 	backend := beam.NewServer()
-	backend.OnVerb(beam.Spawn, beam.Handler(func(ctx *beam.Message) error {
-		if len(ctx.Args) != 2 {
-			return fmt.Errorf("orchard: spawn expects 2 arguments: API token and name of host")
+	backend.OnSpawn(func(cmd ...string) (beam.Sender, error) {
+		if len(cmd) != 2 {
+			return nil, fmt.Errorf("orchard: spawn expects 2 arguments: API token and name of host")
 		}
-		apiToken, hostName := ctx.Args[0], ctx.Args[1]
+		apiToken, hostName := cmd[0], cmd[1]
 
 		apiClient := &api.HTTPClient{
 			BaseURL: "https://api.orchardup.com/v2",
@@ -26,13 +26,13 @@ func Orchard() beam.Sender {
 
 		host, err := apiClient.GetHost(hostName)
 		if err != nil {
-			return err
+			return nil, err
 		}
 
 		url := fmt.Sprintf("tcp://%s:4243", host.IPAddress)
 		tlsConfig, err := getTLSConfig([]byte(host.ClientCert), []byte(host.ClientKey))
 		if err != nil {
-			return err
+			return nil, err
 		}
 
 		backend := DockerClientWithConfig(&DockerClientConfig{
@@ -43,12 +43,11 @@ func Orchard() beam.Sender {
 		forwardBackend := beam.Obj(backend)
 		forwardInstance, err := forwardBackend.Spawn(url)
 		if err != nil {
-			return err
+			return nil, err
 		}
 
-		_, err = ctx.Ret.Send(&beam.Message{Verb: beam.Ack, Ret: forwardInstance})
-		return err
-	}))
+		return forwardInstance, nil
+	})
 	return backend
 }