VM global_env sync + isomorphic nav store primitives

Reverse hook syncs VM GLOBAL_SET mutations back to global_env so CEK reads
see JIT-written values. Isomorphic nav: store primitives, event-bridge,
client? predicate. Browser JS and bytecode rebuilt.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hosts/ocaml/browser/sx_browser.ml

@@ -223,6 +223,13 @@ let () =
     if env == global_env then
       Hashtbl.replace _vm_globals name v)
 
+(* Reverse hook: sync VM GLOBAL_SET mutations back to global_env.
+   Without this, set! inside JIT-compiled functions writes to _vm_globals
+   but leaves global_env stale — CEK reads then see the old value. *)
+let () =
+  Sx_types._vm_global_set_hook := Some (fun name v ->
+    Hashtbl.replace global_env.bindings (Sx_types.intern name) v)
+
 (* ================================================================== *)
 (* Core API                                                            *)
 (* ================================================================== *)

hosts/ocaml/lib/sx_runtime.ml

@@ -50,7 +50,12 @@ let sx_call f args =
     Thunk (l.l_body, local)
   | Continuation (k, _) ->
     k (match args with x :: _ -> x | [] -> Nil)
-  | _ -> raise (Eval_error ("Not callable: " ^ inspect f))
+  | _ ->
+    let nargs = List.length args in
+    let args_preview = if nargs = 0 then "" else
+      let s = String.concat ", " (List.map (fun a -> let s = inspect a in if String.length s > 40 then String.sub s 0 40 ^ ".." else s) args) in
+      " with args=[" ^ s ^ "]" in
+    raise (Eval_error ("Not callable: " ^ inspect f ^ args_preview))
 
 (* Initialize forward ref so primitives can call SX functions *)
 let () = Sx_primitives._sx_call_fn := sx_call

hosts/ocaml/lib/sx_types.ml

@@ -185,8 +185,18 @@ let make_env () =
 let env_extend parent =
   { bindings = Hashtbl.create 16; parent = Some parent }
 
+(* Optional hook: called after every env_bind with (env, name, value).
+   Used by browser kernel to sync VM globals table. *)
+let _env_bind_hook : (env -> string -> value -> unit) option ref = ref None
+
+(* Optional hook: called after VM GLOBAL_SET writes to vm.globals.
+   Used by browser kernel to sync mutations back to global_env. *)
+let _vm_global_set_hook : (string -> value -> unit) option ref = ref None
+
 let env_bind env name v =
-  Hashtbl.replace env.bindings (intern name) v; Nil
+  Hashtbl.replace env.bindings (intern name) v;
+  (match !_env_bind_hook with Some f -> f env name v | None -> ());
+  Nil
 
 (* Internal: scope-chain lookup with pre-interned ID *)
 let rec env_has_id env id =

hosts/ocaml/lib/sx_vm.ml

@@ -303,7 +303,11 @@ and run vm =
               in find_env env
             | None -> false
           in
-          if not written then Hashtbl.replace vm.globals name (peek vm)
+          if not written then begin
+            let v = peek vm in
+            Hashtbl.replace vm.globals name v;
+            (match !Sx_types._vm_global_set_hook with Some f -> f name v | None -> ())
+          end
 
         (* ---- Control flow ---- *)
         | 32 (* OP_JUMP *) ->