diff --git a/examples/echo/main.go b/examples/echo/main.go
index 452460d..d61d429 100644
--- a/examples/echo/main.go
+++ b/examples/echo/main.go
@@ -6,6 +6,8 @@ import (
 	"flag"
 	"io"
 	"os"
+
+	"github.com/wetware/go/std/system"
 )
 
 //export echo
@@ -25,8 +27,16 @@ func main() {
 	}
 
 	if *serve {
-		// Signal to caller that this module is ready to handle
-		// incoming method calls.
-		os.Exit(0x00ff0000)
+		// Yield control to the scheduler.
+		os.Exit(system.StatusAwaiting)
+		// The caller will intercept interface{ExitCode() uint32} and
+		// check if e.ExitCode() == system.StatusAwaiting.
+		//
+		// The top-level command will block until the runtime context
+		// expires.
 	}
+
+	// Implicit status code 0 works as expected.
+	// Caller will resolve to err = nil.
+	// Top-level CLI command will unblock.
 }
diff --git a/std/system/system.go b/std/system/system.go
new file mode 100644
index 0000000..2b60aee
--- /dev/null
+++ b/std/system/system.go
@@ -0,0 +1,3 @@
+package system
+
+const StatusAwaiting = 0x00ff0000
diff --git a/ww.go b/ww.go
index 5beeeef..ef8ad6c 100644
--- a/ww.go
+++ b/ww.go
@@ -8,6 +8,7 @@ import (
 	"github.com/blang/semver/v4"
 	"github.com/tetratelabs/wazero"
 	"github.com/wetware/go/proc"
+	guest "github.com/wetware/go/std/system"
 	"github.com/wetware/go/system"
 
 	protoutils "github.com/wetware/go/util/proto"
@@ -68,7 +69,7 @@ func (env Env) Bind(ctx context.Context, r wazero.Runtime) error {
 		switch e.ExitCode() {
 		case 0:
 			return nil
-		case ExitCodePivot:
+		case guest.StatusAwaiting:
 			return env.Net.ServeProc(ctx, p)
 		}
 	}