Merge branch 'loops/sx-vm-extensions' into scratch/host-jit

# Conflicts:
#	hosts/ocaml/bin/sx_server.ml
#	lib/erlang/runtime.sx

hosts/ocaml/bin/integration_tests.ml

@@ -263,7 +263,7 @@ let make_integration_env () =
 
   (* Type predicates — needed by adapter-sx.sx *)
   bind "callable?" (fun args ->
-    match args with [NativeFn _] | [Lambda _] | [Component _] | [Island _] -> Bool true | _ -> Bool false);
+    match args with [NativeFn _] | [Lambda _] | [Component _] | [Island _] | [VmClosure _] -> Bool true | _ -> Bool false);
   bind "lambda?" (fun args -> match args with [Lambda _] -> Bool true | _ -> Bool false);
   bind "macro?" (fun args -> match args with [Macro _] -> Bool true | _ -> Bool false);
   bind "island?" (fun args -> match args with [Island _] -> Bool true | _ -> Bool false);

hosts/ocaml/bin/mcp_tree.ml

@@ -477,7 +477,7 @@ let setup_env () =
   bind "number?" (fun args -> match args with
     | [Number _] -> Bool true | _ -> Bool false);
   bind "callable?" (fun args -> match args with
-    | [NativeFn _ | Lambda _ | Component _ | Island _] -> Bool true | _ -> Bool false);
+    | [NativeFn _ | Lambda _ | Component _ | Island _ | VmClosure _] -> Bool true | _ -> Bool false);
   bind "empty?" (fun args -> match args with
     | [List []] | [ListRef { contents = [] }] -> Bool true
     | [Nil] -> Bool true | _ -> Bool false);

hosts/ocaml/bin/run_tests.ml

@@ -595,7 +595,7 @@ let make_test_env () =
   (* regex-find-all now provided by sx_primitives.ml *)
   bind "callable?" (fun args ->
     match args with
-    | [NativeFn _] | [Lambda _] | [Component _] | [Island _] -> Bool true
+    | [NativeFn _] | [Lambda _] | [Component _] | [Island _] | [VmClosure _] -> Bool true
     | _ -> Bool false);
   bind "make-sx-expr" (fun args -> match args with [String s] -> SxExpr s | _ -> raise (Eval_error "make-sx-expr: expected string"));
   bind "sx-expr-source" (fun args -> match args with [SxExpr s] -> String s | [String s] -> String s | _ -> raise (Eval_error "sx-expr-source: expected sx-expr or string"));

hosts/ocaml/bin/sx_server.ml

@@ -1138,7 +1138,11 @@ let setup_introspection env =
   bind "component?" (fun args ->
     match args with [Component _] | [Island _] -> Bool true | _ -> Bool false);
   bind "callable?" (fun args ->
-    match args with [NativeFn _] | [Lambda _] | [Component _] | [Island _] -> Bool true | _ -> Bool false);
+    (* VmClosure must count as callable: a JIT-compiled higher-order function
+       returns its inner closure as a VmClosure, and downstream code (e.g.
+       scheme-apply's `(callable? proc)` guard) must recognize it — it is
+       invocable via the normal call path. *)
+    match args with [NativeFn _] | [Lambda _] | [Component _] | [Island _] | [VmClosure _] -> Bool true | _ -> Bool false);
   bind "spread?" (fun args -> match args with [Spread _] -> Bool true | _ -> Bool false);
   bind "continuation?" (fun args ->
     match args with [Continuation _] -> Bool true | [_] -> Bool false | _ -> Bool false);
@@ -1523,6 +1527,22 @@ let sx_render_to_html expr env =
 
 let _jit_warned : (string, bool) Hashtbl.t = Hashtbl.create 16
 
+(* Bisection aid: env-var-driven JIT filter. Lets us narrow which named
+   lambda the VM miscompiles without rebuilding.
+   SX_JIT_DENY=name1,name2  — never JIT these (substring match on exact name).
+   SX_JIT_ONLY=name1,name2  — JIT ONLY these (exact name); skip all others. *)
+let _jit_deny_set =
+  match Sys.getenv_opt "SX_JIT_DENY" with
+  | None | Some "" -> []
+  | Some s -> String.split_on_char ',' s |> List.map String.trim
+let _jit_only_set =
+  match Sys.getenv_opt "SX_JIT_ONLY" with
+  | None | Some "" -> []
+  | Some s -> String.split_on_char ',' s |> List.map String.trim
+let _jit_name_allowed name =
+  (not (List.mem name _jit_deny_set))
+  && (match _jit_only_set with [] -> true | only -> List.mem name only)
+
 let rec make_vm_suspend_marker request saved_vm =
   let d = Hashtbl.create 3 in
   Hashtbl.replace d "__vm_suspended" (Bool true);
@@ -1541,6 +1561,8 @@ let rec make_vm_suspend_marker request saved_vm =
 let register_jit_hook env =
   Sx_runtime._jit_try_call_fn := Some (fun f args ->
     match f with
+    | Lambda l when (match l.l_name with Some n -> not (_jit_name_allowed n) | None -> false) ->
+      None  (* bisection filter excluded this name *)
     | Lambda l ->
       (match l.l_compiled with
        | Some cl when not (Sx_vm.is_jit_failed cl) ->
@@ -4917,6 +4939,38 @@ let () =
       match args with
       | expr :: _ -> String (sx_render_to_html expr env)
       | _ -> raise (Eval_error "render-page: (expr)"))));
+    (* JIT in the epoch serving mode is OPT-IN via SX_SERVING_JIT=1.
+       Default OFF: this mode is the shared command channel used by every
+       loop's conformance runner, and enabling JIT globally regresses
+       continuation-based guest interpreters (Scheme/Erlang/Prolog/CL: their
+       eval/dispatch cores capture call/cc continuations the stack VM can't
+       escape, and deep AST recursion can miscompile into a non-terminating
+       loop). Guests that are safe declare their interpret-only namespace with
+       `(jit-exclude! "<ns>-*")`; until every guest is validated, the safe
+       default is no JIT here. Opt in (SX_SERVING_JIT=1) for validated
+       workloads — e.g. the content/Smalltalk page server. *)
+    (match Sys.getenv_opt "SX_SERVING_JIT" with
+     | Some ("1" | "true" | "yes" | "on") ->
+       (* Load the SX bytecode compiler (lib/compiler.sx) as `compile` — the
+          native Sx_compiler.compile is an incomplete stub (arity-0 bytecode,
+          params as GLOBAL_GET). http/cli/site modes already load it. *)
+       (_import_env := Some env;
+        let project_dir = try Sys.getenv "SX_PROJECT_DIR" with Not_found ->
+          try Sys.getenv "SX_ROOT" with Not_found ->
+          if Sys.file_exists "/app/spec" then "/app" else Sys.getcwd () in
+        let lib_base = try Sys.getenv "SX_LIB_DIR" with Not_found ->
+          project_dir ^ "/lib" in
+        let compiler_path = lib_base ^ "/compiler.sx" in
+        let compiler_path =
+          if Sys.file_exists compiler_path then compiler_path
+          else if Sys.file_exists "lib/compiler.sx" then "lib/compiler.sx"
+          else compiler_path in
+        try load_library_file compiler_path; rebind_host_extensions env
+        with exn ->
+          Printf.eprintf "[sx-server] WARNING: failed to load compiler.sx for JIT (%s) — JIT disabled\n%!"
+            (Printexc.to_string exn));
+       register_jit_hook env
+     | _ -> ());
     send "(ready)";
     (* Main command loop *)
     try