diff --git a/beam/beam.go b/beam/beam.go
index fab5f62..b1e4667 100644
--- a/beam/beam.go
+++ b/beam/beam.go
@@ -24,6 +24,11 @@ type SendCloser interface {
 	Close() error
 }
 
+type ReceiveSender interface {
+	Receiver
+	Sender
+}
+
 func SendPipe(dst Sender, data []byte) (*os.File, error) {
 	r, w, err := os.Pipe()
 	if err != nil {
@@ -111,3 +116,20 @@ func MsgDesc(payload []byte, attachment *os.File) string {
 	}
 	return fmt.Sprintf("'%s'[%s]", payload, filedesc)
 }
+
+type devnull struct{}
+
+func Devnull() ReceiveSender {
+	return devnull{}
+}
+
+func (d devnull) Send(p []byte, a *os.File) error {
+	if a != nil {
+		a.Close()
+	}
+	return nil
+}
+
+func (d devnull) Receive() ([]byte, *os.File, error) {
+	return nil, nil, io.EOF
+}
diff --git a/beam/examples/beamsh/beamsh.go b/beam/examples/beamsh/beamsh.go
index af20916..c444d0a 100644
--- a/beam/examples/beamsh/beamsh.go
+++ b/beam/examples/beamsh/beamsh.go
@@ -23,9 +23,19 @@ var rootPlugins = []string{
 
 var (
 	flX bool
+	flPing bool
+	introspect beam.ReceiveSender = beam.Devnull()
 )
 
 func main() {
+	fd3 := os.NewFile(3, "beam-introspect")
+	if introsp, err := beam.FileConn(fd3); err == nil {
+		introspect = introsp
+		Logf("introspection enabled\n")
+	} else {
+		Logf("introspection disabled\n")
+	}
+	fd3.Close()
 	flag.BoolVar(&flX, "x", false, "print commands as they are being executed")
 	flag.Parse()
 	if flag.NArg() == 0{
@@ -33,7 +43,7 @@ func main() {
 			// No arguments, stdin is terminal --> interactive mode
 			input := bufio.NewScanner(os.Stdin)
 			for {
-				os.Stdout.Write([]byte("beamsh> "))
+				fmt.Printf("[%d] beamsh> ", os.Getpid())
 				if !input.Scan() {
 					break
 				}
@@ -103,11 +113,34 @@ func executeRootScript(script []*dockerscript.Command) error {
 		lastCmd.Children = script
 		script = []*dockerscript.Command{rootCmd}
 	}
-	handlers, err := Handlers()
+	handlers, err := Handlers(introspect)
 	if err != nil {
 		return err
 	}
 	defer handlers.Close()
+	var tasks sync.WaitGroup
+	defer func() {
+		Debugf("Waiting for introspection...\n")
+		tasks.Wait()
+		Debugf("DONE Waiting for introspection\n")
+	}()
+	if introspect != nil {
+		tasks.Add(1)
+		go func() {
+			Debugf("starting introspection\n")
+			defer Debugf("done with introspection\n")
+			defer tasks.Done()
+			introspect.Send(data.Empty().Set("cmd", "log", "stdout").Set("message", "introspection worked!").Bytes(), nil)
+			Debugf("XXX starting reading introspection messages\n")
+			r := beam.NewRouter(handlers)
+			r.NewRoute().All().Handler(func(p []byte, a *os.File) error {
+				Logf("[INTROSPECTION] %s\n", beam.MsgDesc(p, a))
+				return handlers.Send(p, a)
+			})
+			n, err := beam.Copy(r, introspect)
+			Debugf("XXX done reading %d introspection messages: %v\n", n, err)
+		}()
+	}
 	if err := executeScript(handlers, script); err != nil {
 		return err
 	}
@@ -188,7 +221,7 @@ func executeCommand(out beam.Sender, cmd *dockerscript.Command) error {
 type Handler func([]string, io.Writer, io.Writer, beam.Receiver, beam.Sender)
 
 
-func Handlers() (*beam.UnixConn, error) {
+func Handlers(sink beam.Sender) (*beam.UnixConn, error) {
 	var tasks sync.WaitGroup
 	pub, priv, err := beam.USocketPair()
 	if err != nil {
@@ -202,15 +235,16 @@ func Handlers() (*beam.UnixConn, error) {
 			priv.CloseWrite()
 			Debugf("[handlers] done closewrite() on endpoint\n")
 		}()
-		for {
-			Debugf("[handlers] waiting for next job...\n")
-			payload, conn, err := beam.ReceiveConn(priv)
-			Debugf("[handlers] ReceiveConn() returned %v\n", err)
+		r := beam.NewRouter(sink)
+		r.NewRoute().HasAttachment().KeyIncludes("type", "job").Handler(func(payload []byte, attachment *os.File) error {
+			conn, err := beam.FileConn(attachment)
 			if err != nil {
-				return
+				attachment.Close()
+				return err
 			}
+			// attachment.Close()
 			tasks.Add(1)
-			go func(payload []byte, conn *beam.UnixConn) {
+			go func() {
 				defer tasks.Done()
 				defer func() {
 					Debugf("[handlers] '%s' closewrite\n", payload)
@@ -239,8 +273,10 @@ func Handlers() (*beam.UnixConn, error) {
 				Debugf("[handlers] calling %s\n", strings.Join(cmd, " "))
 				handler(cmd, stdout, stderr, beam.Receiver(conn), beam.Sender(conn))
 				Debugf("[handlers] returned: %s\n", strings.Join(cmd, " "))
-			}(payload, conn)
-		}
+			}()
+			return nil
+		})
+		beam.Copy(r, priv)
 		Debugf("[handlers] waiting for all tasks\n")
 		tasks.Wait()
 		Debugf("[handlers] all tasks returned\n")
@@ -285,6 +321,8 @@ func GetHandler(name string) Handler {
 		return CmdConnect
 	} else if name == "openfile" {
 		return CmdOpenfile
+	} else if name == "spawn" {
+		return CmdSpawn
 	}
 	return nil
 }
diff --git a/beam/examples/beamsh/builtins.go b/beam/examples/beamsh/builtins.go
index da767f1..d4e084d 100644
--- a/beam/examples/beamsh/builtins.go
+++ b/beam/examples/beamsh/builtins.go
@@ -6,6 +6,7 @@ import (
 	"github.com/dotcloud/docker/pkg/beam"
 	"github.com/dotcloud/docker/pkg/beam/data"
 	"github.com/dotcloud/docker/pkg/term"
+	"github.com/dotcloud/docker/utils"
 	"text/template"
 	"fmt"
 	"sync"
@@ -167,6 +168,27 @@ func CmdPass(args []string, stdout, stderr io.Writer, in beam.Receiver, out beam
 	}
 }
 
+func CmdSpawn(args []string, stdout, stderr io.Writer, in beam.Receiver, out beam.Sender) {
+	c := exec.Command(utils.SelfPath())
+	r, w, err := os.Pipe()
+	if err != nil {
+		fmt.Fprintf(stderr, "%v\n", err)
+		return
+	}
+	c.Stdin = r
+	c.Stdout = stdout
+	c.Stderr = stderr
+	go func() {
+		fmt.Fprintf(w, strings.Join(args[1:], " "))
+		w.Sync()
+		w.Close()
+	}()
+	if err := c.Run(); err != nil {
+		fmt.Fprintf(stderr, "%v\n", err)
+		return
+	}
+}
+
 func CmdIn(args []string, stdout, stderr io.Writer, in beam.Receiver, out beam.Sender) {
 	os.Chdir(args[1])
 	GetHandler("pass")([]string{"pass"}, stdout, stderr, in, out)
@@ -176,8 +198,46 @@ func CmdExec(args []string, stdout, stderr io.Writer, in beam.Receiver, out beam
 	cmd := exec.Command(args[1], args[2:]...)
 	cmd.Stdout = stdout
 	cmd.Stderr = stderr
-	cmd.Stdin = os.Stdin
+	//cmd.Stdin = os.Stdin
+	local, remote, err := beam.SocketPair()
+	if err != nil {
+		fmt.Fprintf(stderr, "%v\n", err)
+		return
+	}
+	child, err := beam.FileConn(local)
+	if err != nil {
+		local.Close()
+		remote.Close()
+		fmt.Fprintf(stderr, "%v\n", err)
+		return
+	}
+	local.Close()
+	cmd.ExtraFiles = append(cmd.ExtraFiles, remote)
+
+	var tasks sync.WaitGroup
+	tasks.Add(1)
+	go func() {
+		defer Debugf("done copying to child\n")
+		defer tasks.Done()
+		defer child.CloseWrite()
+		beam.Copy(child, in)
+	}()
+
+	tasks.Add(1)
+	go func() {
+		defer Debugf("done copying from child %d\n")
+		defer tasks.Done()
+		r := beam.NewRouter(out)
+		r.NewRoute().All().Handler(func(p []byte, a *os.File) error {
+			return out.Send(data.Message(p).Set("pid", fmt.Sprintf("%d", cmd.Process.Pid)).Bytes(), a)
+		})
+		beam.Copy(r, child)
+	}()
 	execErr := cmd.Run()
+	// We can close both ends of the socket without worrying about data stuck in the buffer,
+	// because unix socket writes are fully synchronous.
+	child.Close()
+	tasks.Wait()
 	var status string
 	if execErr != nil {
 		status = execErr.Error()
@@ -190,7 +250,11 @@ func CmdExec(args []string, stdout, stderr io.Writer, in beam.Receiver, out beam
 func CmdTrace(args []string, stdout, stderr io.Writer, in beam.Receiver, out beam.Sender) {
 	r := beam.NewRouter(out)
 	r.NewRoute().All().Handler(func(payload []byte, attachment *os.File) error {
-		fmt.Printf("===> %s\n", beam.MsgDesc(payload, attachment))
+		var sfd string = "nil"
+		if attachment != nil {
+			sfd = fmt.Sprintf("%d", attachment.Fd())
+		}
+		fmt.Printf("===> %s [%s]\n", data.Message(payload).Pretty(), sfd)
 		out.Send(payload, attachment)
 		return nil
 	})
diff --git a/beam/router.go b/beam/router.go
index e19ec9d..abdfe61 100644
--- a/beam/router.go
+++ b/beam/router.go
@@ -27,7 +27,7 @@ func (r *Router) Send(payload []byte, attachment *os.File) (err error) {
 		}
 	}
 	if r.sink != nil {
-		//fmt.Printf("[Router.Send] no match. sending to sink\n")
+		// fmt.Printf("[%d] [Router.Send] no match. sending %s to sink %#v\n", os.Getpid(), MsgDesc(payload, attachment), r.sink)
 		return r.sink.Send(payload, attachment)
 	}
 	//fmt.Printf("[Router.Send] no match. return error.\n")
@@ -101,9 +101,17 @@ func (route *Route) Tee(dst Sender) *Route {
 	return route
 }
 
+func (r *Route) Filter(f func([]byte, *os.File) bool) *Route {
+	r.rules = append(r.rules, f)
+	return r
+}
+
 func (r *Route) KeyStartsWith(k string, beginning ...string) *Route {
 	r.rules = append(r.rules, func(payload []byte, attachment *os.File) bool {
 		values := data.Message(payload).Get(k)
+		if values == nil {
+			return false
+		}
 		if len(values) < len(beginning) {
 			return false
 		}
@@ -117,6 +125,7 @@ func (r *Route) KeyStartsWith(k string, beginning ...string) *Route {
 	return r
 }
 
+
 func (r *Route) KeyEquals(k string, full...string) *Route {
 	r.rules = append(r.rules, func(payload []byte, attachment *os.File) bool {
 		values := data.Message(payload).Get(k)
@@ -152,6 +161,13 @@ func (r *Route) NoKey(k string) *Route {
 	return r
 }
 
+func (r *Route) KeyExists(k string) *Route {
+	r.rules = append(r.rules, func(payload []byte, attachment *os.File) bool {
+		return data.Message(payload).Get(k) != nil
+	})
+	return r
+}
+
 func (r *Route) Passthrough(dst Sender) *Route {
 	r.handler = func(payload []byte, attachment *os.File) error {
 		return dst.Send(payload, attachment)