diff --git a/os2.rkt b/os2.rkt
index f826392..371e572 100644
--- a/os2.rkt
+++ b/os2.rkt
@@ -6,6 +6,33 @@
 (require (only-in racket/list flatten))
 (require "unify.rkt")
 
+(provide nested-vm
+	 ground-vm
+
+	 (struct-out topic)
+	 topic-publisher
+	 topic-subscriber
+	 co-roles
+	 co-topics
+
+	 (struct-out handlers)
+
+	 (except-out (struct-out transition) transition)
+	 (rename-out [make-transition transition])
+	 extend-transition
+
+	 (except-out (struct-out add-role) add-role)
+	 (rename-out [make-add-role add-role])
+	 (except-out (struct-out delete-role) delete-role)
+	 (rename-out [make-delete-role delete-role])
+	 (struct-out send-message)
+	 (except-out (struct-out spawn) spawn)
+	 (rename-out [make-spawn spawn])
+	 (except-out (struct-out kill) kill)
+	 (rename-out [make-kill kill])
+
+	 (struct-out at-meta-level))
+
 ;; Endpoints are the units of deduplication.
 ;; Flows (in canonical form) are the units of presence.
 
@@ -69,6 +96,19 @@
 ;; An Action is either a Preaction or an (at-meta-level Preaction).
 (struct at-meta-level (preaction) #:prefab)
 
+;;---------------------------------------------------------------------------
+
+(define (make-transition state . actions) (transition state actions))
+(define (make-add-role topic handlers [k #f]) (add-role topic handlers k))
+(define (make-delete-role eid [reason #f]) (delete-role eid reason))
+(define (make-spawn thunk [k #f]) (spawn thunk k))
+(define (make-kill [pid #f] [reason #f]) (kill pid reason))
+
+(define (extend-transition t . more-actions)
+  (match t
+    [(transition state actions) (transition state (list actions more-actions))]
+    [state (transition state more-actions)]))
+
 ;;---------------------------------------------------------------------------
 ;; Topics and roles
 
@@ -307,7 +347,8 @@
      (spawn thunk (wrap-trapk pid k))]
     [(? kill?) preaction]))
 
-;;---------------------------------------------------------------------------
+(define (nested-vm boot)
+  (lambda () (run-vm (make-vm boot))))
 
 (define (ground-vm boot)
   (let run-kernel ((transition (run-vm (make-vm boot)))