diff --git a/hosts/ocaml/bin/run_tests.ml b/hosts/ocaml/bin/run_tests.ml
index 4f9e891a..3b3ec8f4 100644
--- a/hosts/ocaml/bin/run_tests.ml
+++ b/hosts/ocaml/bin/run_tests.ml
@@ -1072,6 +1072,25 @@ let run_spec_tests env test_files =
   (* Pre-load test-handlers.sx so its mock definitions (reset-mocks!, helper, etc.)
      are available to test-examples.sx which loads before it alphabetically *)
   load_module "test-handlers.sx" web_tests_dir;
+
+  (* Re-bind render-to-sx AFTER adapter-sx.sx has loaded, wrapping the SX version.
+     The SX render-to-sx handles AST inputs; we add string→parse→aser support. *)
+  let sx_render_to_sx = try Some (Sx_types.env_get env "render-to-sx") with _ -> None in
+  ignore (Sx_types.env_bind env "render-to-sx" (NativeFn ("render-to-sx", fun args ->
+    match args with
+    | [String src] ->
+      (* String input: parse then evaluate via aser *)
+      let exprs = Sx_parser.parse_all src in
+      let expr = match exprs with [e] -> e | es -> List (Symbol "do" :: es) in
+      let result = eval_expr (List [Symbol "aser"; expr; Env env]) (Env env) in
+      (match result with SxExpr s -> String s | String s -> String s | _ -> String (Sx_runtime.value_to_str result))
+    | _ ->
+      (* AST input: delegate to the SX render-to-sx *)
+      match sx_render_to_sx with
+      | Some (NativeFn (_, f)) -> f args
+      | Some (Lambda _ as fn) -> Sx_ref.cek_call fn (List args)
+      | _ -> String "")));
+
   let files = if test_files = [] then begin
     (* Spec tests (core language — always run) *)
     let spec_entries = Sys.readdir spec_tests_dir in