OCaml CEK machine compiled to WebAssembly for browser execution

- wasm_of_ocaml compiles OCaml SX engine to WASM (722/722 spec tests) - js_of_ocaml fallback also working (722/722 spec tests) - Thin JS platform layer (sx-platform.js) with ~80 DOM/browser natives - Lambda callback bridge: SX lambdas callable from JS via handle table - Side-channel pattern bypasses js_of_ocaml return-value property stripping - Web adapters (signals, deps, router, adapter-html) load as SX source - Render mode dispatch: HTML tags + fragments route to OCaml renderer - Island/component accessors handle both Component and Island types - Dict-based signal support (signals.sx creates dicts, not native Signal) - Scope stack implementation (collect!/collected/emit!/emitted/context) - Bundle script embeds web adapters + WASM loader + platform layer - SX_USE_WASM env var toggles WASM engine in dev/production - Bootstrap extended: --web flag transpiles web adapters, :effects stripping Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-03-16 07:13:49 +00:00
44 changed files with 5167 additions and 171 deletions
--- a/docker-compose.dev-sx.yml
+++ b/docker-compose.dev-sx.yml
@@ -16,6 +16,7 @@ services:
      SX_USE_OCAML: "1"
      SX_OCAML_BIN: "/app/bin/sx_server"
      SX_BOUNDARY_STRICT: "1"
+      SX_USE_WASM: "1"
      SX_DEV: "1"
    volumes:
      - /root/rose-ash/_config/dev-sh-config.yaml:/app/config/app-config.yaml:ro
--- a/hosts/ocaml/bin/debug_set.ml
+++ b/hosts/ocaml/bin/debug_set.ml
@@ -1,6 +1,6 @@
-module T = Sx.Sx_types
-module P = Sx.Sx_parser
-module R = Sx.Sx_ref
+module T = Sx_types
+module P = Sx_parser
+module R = Sx_ref
 open T

 let () =
--- a/hosts/ocaml/bin/run_tests.ml
+++ b/hosts/ocaml/bin/run_tests.ml
@@ -10,13 +10,6 @@
      dune exec bin/run_tests.exe -- test-primitives  # specific test
      dune exec bin/run_tests.exe -- --foundation     # foundation only *)

-module Sx_types = Sx.Sx_types
-module Sx_parser = Sx.Sx_parser
-module Sx_primitives = Sx.Sx_primitives
-module Sx_runtime = Sx.Sx_runtime
-module Sx_ref = Sx.Sx_ref
-module Sx_render = Sx.Sx_render
-
 open Sx_types
 open Sx_parser
 open Sx_primitives
@@ -267,7 +260,7 @@ let make_test_env () =
    | _ -> raise (Eval_error "append!: expected list and value"));

  (* --- HTML Renderer (from sx_render.ml library module) --- *)
-  Sx.Sx_render.setup_render_env env;
+  Sx_render.setup_render_env env;

  (* --- Missing primitives referenced by tests --- *)

--- a/hosts/ocaml/bin/sx_server.ml
+++ b/hosts/ocaml/bin/sx_server.ml
@@ -14,13 +14,6 @@
    IO primitives (query, action, request-arg, request-method, ctx)
    yield (io-request ...) and block on stdin for (io-response ...). *)

-module Sx_types = Sx.Sx_types
-module Sx_parser = Sx.Sx_parser
-module Sx_primitives = Sx.Sx_primitives
-module Sx_runtime = Sx.Sx_runtime
-module Sx_ref = Sx.Sx_ref
-module Sx_render = Sx.Sx_render
-
 open Sx_types


--- a/hosts/ocaml/bootstrap.py
+++ b/hosts/ocaml/bootstrap.py
@@ -22,14 +22,22 @@ from shared.sx.types import Symbol


 def extract_defines(source: str) -> list[tuple[str, list]]:
-    """Parse .sx source, return list of (name, define-expr) for top-level defines."""
+    """Parse .sx source, return list of (name, define-expr) for top-level defines.
+    Strips :effects [...] annotations from defines."""
+    from shared.sx.types import Keyword
    exprs = parse_all(source)
    defines = []
    for expr in exprs:
        if isinstance(expr, list) and expr and isinstance(expr[0], Symbol):
            if expr[0].name == "define":
                name = expr[1].name if isinstance(expr[1], Symbol) else str(expr[1])
-                defines.append((name, expr))
+                # Strip :effects [...] annotation if present
+                # (define name :effects [...] body) → (define name body)
+                cleaned = list(expr)
+                if (len(cleaned) >= 4 and isinstance(cleaned[2], Keyword)
+                        and cleaned[2].name == "effects"):
+                    cleaned = [cleaned[0], cleaned[1]] + cleaned[4:]
+                defines.append((name, cleaned))
    return defines


@@ -50,7 +58,7 @@ let trampoline v = v  (* CEK machine doesn't produce thunks *)
 """


-# OCaml fixups — override iterative CEK run
+# OCaml fixups — override iterative CEK run + reactive subscriber fix
 FIXUPS = """\

 (* Override recursive cek_run with iterative loop *)
@@ -61,6 +69,40 @@ let cek_run_iterative state =
  done;
  cek_value !s

+(* Strict mode refs — used by test runner, stubbed here *)
+let _strict_ref = ref Nil
+let _prim_param_types_ref = ref Nil
+let value_matches_type_p _v _t = Bool true
+
+(* Override reactive_shift_deref to wrap subscriber as NativeFn.
+   The transpiler emits bare OCaml closures for (fn () ...) but
+   signal_add_sub_b expects SX values. *)
+let reactive_shift_deref sig' env kont =
+  let scan_result = kont_capture_to_reactive_reset kont in
+  let captured_frames = first scan_result in
+  let reset_frame = nth scan_result (Number 1.0) in
+  let remaining_kont = nth scan_result (Number 2.0) in
+  let update_fn = get reset_frame (String "update-fn") in
+  let sub_disposers = ref (List []) in
+  let subscriber_fn () =
+    List.iter (fun d -> ignore (cek_call d Nil)) (sx_to_list !sub_disposers);
+    sub_disposers := List [];
+    let new_reset = make_reactive_reset_frame env update_fn (Bool false) in
+    let new_kont = prim_call "concat" [captured_frames; List [new_reset]; remaining_kont] in
+    ignore (with_island_scope
+      (fun d -> sub_disposers := sx_append_b !sub_disposers d; Nil)
+      (fun () -> cek_run (make_cek_value (signal_value sig') env new_kont)));
+    Nil
+  in
+  let subscriber = NativeFn ("reactive-subscriber", fun _args -> subscriber_fn ()) in
+  ignore (signal_add_sub_b sig' subscriber);
+  ignore (register_in_scope (fun () ->
+    ignore (signal_remove_sub_b sig' subscriber);
+    List.iter (fun d -> ignore (cek_call d Nil)) (sx_to_list !sub_disposers);
+    Nil));
+  let initial_kont = prim_call "concat" [captured_frames; List [reset_frame]; remaining_kont] in
+  make_cek_value (signal_value sig') env initial_kont
+
 """


@@ -96,8 +138,15 @@ def compile_spec_to_ml(spec_dir: str | None = None) -> str:
            src = f.read()
        defines = extract_defines(src)

-        # Skip defines provided by preamble or fixups
-        skip = {"trampoline"}
+        # Skip defines provided by preamble/fixups or that belong in web module
+        skip = {"trampoline",
+                # Freeze functions depend on signals.sx (web spec)
+                "freeze-registry", "freeze-signal", "freeze-scope",
+                "cek-freeze-scope", "cek-freeze-all",
+                "cek-thaw-scope", "cek-thaw-all",
+                "freeze-to-sx", "thaw-from-sx",
+                "freeze-to-cid", "thaw-from-cid",
+                "content-hash", "content-put", "content-get", "content-store"}
        defines = [(n, e) for n, e in defines if n not in skip]

        # Deduplicate — keep last definition for each name (CEK overrides tree-walk)
@@ -125,6 +174,160 @@ def compile_spec_to_ml(spec_dir: str | None = None) -> str:
    return "\n".join(parts)


+WEB_PREAMBLE = """\
+(* sx_web.ml — Auto-generated from web adapters by hosts/ocaml/bootstrap.py *)
+(* Do not edit — regenerate with: python3 hosts/ocaml/bootstrap.py --web *)
+
+[@@@warning "-26-27"]
+
+open Sx_types
+open Sx_runtime
+
+"""
+
+# Web adapter files to transpile (dependency order)
+WEB_ADAPTER_FILES = [
+    ("signals.sx", "signals (reactive signal runtime)"),
+    ("deps.sx", "deps (component dependency analysis)"),
+    ("page-helpers.sx", "page-helpers (pure data transformation helpers)"),
+    ("router.sx", "router (client-side route matching)"),
+    ("adapter-html.sx", "adapter-html (HTML rendering adapter)"),
+]
+
+
+def compile_web_to_ml(web_dir: str | None = None) -> str:
+    """Compile web adapter SX files to OCaml source."""
+    from shared.sx.ref.sx_ref import eval_expr, trampoline, make_env, sx_parse
+
+    if web_dir is None:
+        web_dir = os.path.join(_PROJECT, "web")
+
+    # Load the transpiler
+    env = make_env()
+    transpiler_path = os.path.join(_HERE, "transpiler.sx")
+    with open(transpiler_path) as f:
+        transpiler_src = f.read()
+    for expr in sx_parse(transpiler_src):
+        trampoline(eval_expr(expr, env))
+
+    # Also load the evaluator defines so the transpiler knows about them
+    spec_dir = os.path.join(_PROJECT, "spec")
+    eval_path = os.path.join(spec_dir, "evaluator.sx")
+    if os.path.exists(eval_path):
+        with open(eval_path) as f:
+            eval_defines = extract_defines(f.read())
+        eval_names = [n for n, _ in eval_defines]
+    else:
+        eval_names = []
+
+    parts = [WEB_PREAMBLE]
+
+    # Collect all web adapter defines
+    all_defines = []
+    for filename, label in WEB_ADAPTER_FILES:
+        filepath = os.path.join(web_dir, filename)
+        if not os.path.exists(filepath):
+            print(f"Warning: {filepath} not found, skipping", file=sys.stderr)
+            continue
+
+        with open(filepath) as f:
+            src = f.read()
+        defines = extract_defines(src)
+
+        # Deduplicate within file
+        seen = {}
+        for i, (n, e) in enumerate(defines):
+            seen[n] = i
+        defines = [(n, e) for i, (n, e) in enumerate(defines) if seen[n] == i]
+
+        all_defines.extend(defines)
+        print(f"  {filename}: {len(defines)} defines", file=sys.stderr)
+
+    # Deduplicate across files (last wins)
+    seen = {}
+    for i, (n, e) in enumerate(all_defines):
+        seen[n] = i
+    all_defines = [(n, e) for i, (n, e) in enumerate(all_defines) if seen[n] == i]
+
+    print(f"  Total: {len(all_defines)} unique defines", file=sys.stderr)
+
+    # Build the defines list for the transpiler
+    defines_list = [[name, expr] for name, expr in all_defines]
+    env["_defines"] = defines_list
+
+    # Known defines = evaluator names + web adapter names
+    env["_known_defines"] = eval_names + [name for name, _ in all_defines]
+
+    # Translate
+    translate_expr = sx_parse("(ml-translate-file _defines)")[0]
+    result = trampoline(eval_expr(translate_expr, env))
+
+    parts.append("\n(* === Transpiled from web adapters === *)\n")
+    parts.append(result)
+
+    # Registration function — extract actual OCaml names from transpiled output
+    # by using the same transpiler mangling.
+    # Ask the transpiler for the mangled name of each define.
+    name_map = {}
+    for name, _ in all_defines:
+        mangle_expr = sx_parse(f'(ml-mangle "{name}")')[0]
+        mangled = trampoline(eval_expr(mangle_expr, env))
+        name_map[name] = mangled
+
+    def count_params(expr):
+        """Count actual params from a (define name [annotations] (fn (params...) body)) form."""
+        # Find the (fn ...) form — it might be at index 2, 3, or 4 depending on annotations
+        fn_expr = None
+        for i in range(2, min(len(expr), 6)):
+            if (isinstance(expr[i], list) and expr[i] and
+                isinstance(expr[i][0], Symbol) and expr[i][0].name in ("fn", "lambda")):
+                fn_expr = expr[i]
+                break
+        if fn_expr is None:
+            return -1  # not a function
+        params = fn_expr[1] if isinstance(fn_expr[1], list) else []
+        n = 0
+        skip = False
+        for p in params:
+            if skip:
+                skip = False
+                continue
+            if isinstance(p, Symbol) and p.name in ("&key", "&rest"):
+                skip = True
+                continue
+            if isinstance(p, list) and len(p) >= 3:  # (name :as type)
+                n += 1
+            elif isinstance(p, Symbol):
+                n += 1
+        return n
+
+    parts.append("\n\n(* Register all web adapter functions into an environment *)\n")
+    parts.append("let register_web_adapters env =\n")
+    for name, expr in all_defines:
+        mangled = name_map[name]
+        n = count_params(expr)
+        if n < 0:
+            # Non-function define (constant)
+            parts.append(f'  ignore (Sx_types.env_bind env "{name}" {mangled});\n')
+        elif n == 0:
+            parts.append(f'  ignore (Sx_types.env_bind env "{name}" '
+                         f'(NativeFn ("{name}", fun _args -> {mangled} Nil)));\n')
+        else:
+            # Generate match with correct arity
+            arg_names = [chr(97 + i) for i in range(n)]  # a, b, c, ...
+            pat = "; ".join(arg_names)
+            call = " ".join(arg_names)
+            # Pad with Nil for partial application
+            pad_call = " ".join(arg_names[:1] + ["Nil"] * (n - 1)) if n > 1 else arg_names[0]
+            parts.append(f'  ignore (Sx_types.env_bind env "{name}" '
+                         f'(NativeFn ("{name}", fun args -> match args with '
+                         f'| [{pat}] -> {mangled} {call} '
+                         f'| _ -> raise (Eval_error "{name}: expected {n} args"))));\n')
+    parts.append("  ()\n")
+
+    return "\n".join(parts)
+
+
 def main():
    import argparse
    parser = argparse.ArgumentParser(description="Bootstrap SX spec -> OCaml")
@@ -133,17 +336,37 @@ def main():
        default=None,
        help="Output file (default: stdout)",
    )
+    parser.add_argument(
+        "--web",
+        action="store_true",
+        help="Compile web adapters instead of evaluator spec",
+    )
+    parser.add_argument(
+        "--web-output",
+        default=None,
+        help="Output file for web adapters (default: stdout)",
+    )
    args = parser.parse_args()

-    result = compile_spec_to_ml()
-
-    if args.output:
-        with open(args.output, "w") as f:
-            f.write(result)
-        size = os.path.getsize(args.output)
-        print(f"Wrote {args.output} ({size} bytes)", file=sys.stderr)
+    if args.web or args.web_output:
+        result = compile_web_to_ml()
+        out = args.web_output or args.output
+        if out:
+            with open(out, "w") as f:
+                f.write(result)
+            size = os.path.getsize(out)
+            print(f"Wrote {out} ({size} bytes)", file=sys.stderr)
+        else:
+            print(result)
    else:
-        print(result)
+        result = compile_spec_to_ml()
+        if args.output:
+            with open(args.output, "w") as f:
+                f.write(result)
+            size = os.path.getsize(args.output)
+            print(f"Wrote {args.output} ({size} bytes)", file=sys.stderr)
+        else:
+            print(result)


 if __name__ == "__main__":
--- a/hosts/ocaml/browser/build.sh
+++ b/hosts/ocaml/browser/build.sh
@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+# Build the OCaml SX engine for browser use (WASM + JS fallback).
+#
+# Outputs:
+#   _build/default/browser/sx_browser.bc.wasm.js       WASM loader
+#   _build/default/browser/sx_browser.bc.wasm.assets/   WASM modules
+#   _build/default/browser/sx_browser.bc.js             JS fallback
+#
+# Usage:
+#   cd hosts/ocaml && ./browser/build.sh
+
+set -euo pipefail
+cd "$(dirname "$0")/.."
+
+eval $(opam env 2>/dev/null || true)
+
+echo "=== Building OCaml SX browser engine ==="
+
+# Build all targets: bytecode, JS, WASM
+dune build browser/sx_browser.bc.js browser/sx_browser.bc.wasm.js
+
+echo ""
+echo "--- Output sizes ---"
+echo -n "JS (unoptimized):  "; ls -lh _build/default/browser/sx_browser.bc.js | awk '{print $5}'
+echo -n "WASM loader:       "; ls -lh _build/default/browser/sx_browser.bc.wasm.js | awk '{print $5}'
+echo -n "WASM modules:      "; du -sh _build/default/browser/sx_browser.bc.wasm.assets/*.wasm | awk '{s+=$1}END{print s"K"}'
+
+# Optimized JS build
+js_of_ocaml --opt=3 -o _build/default/browser/sx_browser.opt.js _build/default/browser/sx_browser.bc
+echo -n "JS (optimized):    "; ls -lh _build/default/browser/sx_browser.opt.js | awk '{print $5}'
+
+echo ""
+echo "=== Build complete ==="
+echo ""
+echo "Test with:"
+echo "  node hosts/ocaml/browser/run_tests_js.js                                    # JS"
+echo "  node --experimental-wasm-imported-strings hosts/ocaml/browser/run_tests_wasm.js  # WASM"
--- a/hosts/ocaml/browser/bundle.sh
+++ b/hosts/ocaml/browser/bundle.sh
@@ -0,0 +1,139 @@
+#!/usr/bin/env bash
+# Bundle the WASM engine + platform + web adapters into shared/static/scripts/
+#
+# Usage: hosts/ocaml/browser/bundle.sh
+
+set -euo pipefail
+cd "$(dirname "$0")/../../.."
+
+WASM_LOADER="hosts/ocaml/_build/default/browser/sx_browser.bc.wasm.js"
+WASM_ASSETS="hosts/ocaml/_build/default/browser/sx_browser.bc.wasm.assets"
+PLATFORM="hosts/ocaml/browser/sx-platform.js"
+OUT="shared/static/scripts/sx-wasm.js"
+ASSET_DIR="shared/static/scripts/sx-wasm-assets"
+
+if [ ! -f "$WASM_LOADER" ]; then
+  echo "Build first: cd hosts/ocaml && eval \$(opam env) && dune build browser/sx_browser.bc.wasm.js"
+  exit 1
+fi
+
+# 1. WASM loader (patched asset path)
+sed 's|"src":"sx_browser.bc.wasm.assets"|"src":"sx-wasm-assets"|' \
+  "$WASM_LOADER" > "$OUT"
+
+# 2. Platform layer
+echo "" >> "$OUT"
+cat "$PLATFORM" >> "$OUT"
+
+# 3. Embedded web adapters — SX source as JS string constants
+echo "" >> "$OUT"
+echo "// =========================================================================" >> "$OUT"
+echo "// Embedded web adapters (loaded into WASM engine at boot)" >> "$OUT"
+echo "// =========================================================================" >> "$OUT"
+echo "globalThis.__sxAdapters = {};" >> "$OUT"
+
+# Adapters to embed (order matters for dependencies)
+ADAPTERS="signals deps page-helpers router adapter-html"
+
+for name in $ADAPTERS; do
+  file="web/${name}.sx"
+  if [ -f "$file" ]; then
+    echo -n "globalThis.__sxAdapters[\"${name}\"] = " >> "$OUT"
+    # Escape the SX source for embedding in a JS string
+    python3 -c "
+import json, sys
+with open('$file') as f:
+    print(json.dumps(f.read()) + ';')
+" >> "$OUT"
+  fi
+done
+
+# 4. Boot shim
+cat >> "$OUT" << 'BOOT'
+
+// =========================================================================
+// WASM Boot: load adapters, then process inline <script type="text/sx">
+// =========================================================================
+(function() {
+  "use strict";
+  if (typeof document === "undefined") return;
+
+  function sxWasmBoot() {
+    var K = globalThis.SxKernel;
+    if (!K || !globalThis.Sx) { setTimeout(sxWasmBoot, 50); return; }
+
+    console.log("[sx-wasm] booting, engine:", K.engine());
+
+    // Load embedded web adapters
+    var adapters = globalThis.__sxAdapters || {};
+    var adapterOrder = ["signals", "deps", "page-helpers", "router", "adapter-html"];
+    for (var j = 0; j < adapterOrder.length; j++) {
+      var name = adapterOrder[j];
+      if (adapters[name]) {
+        var r = K.loadSource(adapters[name]);
+        if (typeof r === "string" && r.startsWith("Error:")) {
+          console.error("[sx-wasm] adapter " + name + " error:", r);
+        } else {
+          console.log("[sx-wasm] loaded " + name + " (" + r + " defs)");
+        }
+      }
+    }
+    delete globalThis.__sxAdapters;  // Free memory
+
+    // Process <script type="text/sx" data-components>
+    var scripts = document.querySelectorAll('script[type="text/sx"]');
+    for (var i = 0; i < scripts.length; i++) {
+      var s = scripts[i], src = s.textContent.trim();
+      if (!src) continue;
+      if (s.hasAttribute("data-components")) {
+        var result = K.loadSource(src);
+        if (typeof result === "string" && result.startsWith("Error:"))
+          console.error("[sx-wasm] component load error:", result);
+      }
+    }
+
+    // Process <script type="text/sx" data-init>
+    for (var i = 0; i < scripts.length; i++) {
+      var s = scripts[i];
+      if (s.hasAttribute("data-init")) {
+        var src = s.textContent.trim();
+        if (src) K.loadSource(src);
+      }
+    }
+
+    // Process <script type="text/sx" data-mount="...">
+    for (var i = 0; i < scripts.length; i++) {
+      var s = scripts[i];
+      if (s.hasAttribute("data-mount")) {
+        var mount = s.getAttribute("data-mount"), src = s.textContent.trim();
+        if (!src) continue;
+        var target = mount === "body" ? document.body : document.querySelector(mount);
+        if (!target) continue;
+        try {
+          var parsed = K.parse(src);
+          if (parsed && parsed.length > 0) {
+            var html = K.renderToHtml(parsed[0]);
+            if (html && typeof html === "string") {
+              target.innerHTML = html;
+              console.log("[sx-wasm] mounted to", mount);
+            }
+          }
+        } catch(e) { console.error("[sx-wasm] mount error:", e); }
+      }
+    }
+
+    console.log("[sx-wasm] boot complete");
+  }
+
+  if (document.readyState === "loading") document.addEventListener("DOMContentLoaded", sxWasmBoot);
+  else sxWasmBoot();
+})();
+BOOT
+
+# 5. Copy WASM assets
+mkdir -p "$ASSET_DIR"
+cp "$WASM_ASSETS"/*.wasm "$ASSET_DIR/"
+
+echo "=== Bundle complete ==="
+ls -lh "$OUT"
+echo -n "WASM assets: "; du -sh "$ASSET_DIR" | awk '{print $1}'
--- a/hosts/ocaml/browser/dune
+++ b/hosts/ocaml/browser/dune
@@ -0,0 +1,5 @@
+(executable
+ (name sx_browser)
+ (libraries sx js_of_ocaml)
+ (modes byte js wasm)
+ (preprocess (pps js_of_ocaml-ppx)))
--- a/hosts/ocaml/browser/run_tests_js.js
+++ b/hosts/ocaml/browser/run_tests_js.js
@@ -0,0 +1,149 @@
+#!/usr/bin/env node
+/**
+ * Test runner for the js_of_ocaml-compiled SX engine.
+ *
+ * Loads the OCaml CEK machine (compiled to JS) and runs the spec test suite.
+ *
+ * Usage:
+ *   node hosts/ocaml/browser/run_tests_js.js           # standard tests
+ *   node hosts/ocaml/browser/run_tests_js.js --full     # full suite
+ */
+
+const fs = require("fs");
+const path = require("path");
+
+// Load the compiled OCaml engine
+const enginePath = path.join(__dirname, "../_build/default/browser/sx_browser.bc.js");
+if (!fs.existsSync(enginePath)) {
+  console.error("Build first: cd hosts/ocaml && eval $(opam env) && dune build browser/sx_browser.bc.js");
+  process.exit(1);
+}
+require(enginePath);
+
+const K = globalThis.SxKernel;
+const full = process.argv.includes("--full");
+
+// Test state
+let passed = 0;
+let failed = 0;
+let errors = [];
+let suiteStack = [];
+
+function currentSuite() {
+  return suiteStack.length > 0 ? suiteStack.join(" > ") : "";
+}
+
+// Register platform test functions
+K.registerNative("report-pass", (args) => {
+  const name = typeof args[0] === "string" ? args[0] : JSON.stringify(args[0]);
+  passed++;
+  if (process.env.VERBOSE) {
+    console.log(`  PASS: ${currentSuite()} > ${name}`);
+  } else {
+    process.stdout.write(".");
+    if (passed % 80 === 0) process.stdout.write("\n");
+  }
+  return null;
+});
+
+K.registerNative("report-fail", (args) => {
+  const name = typeof args[0] === "string" ? args[0] : JSON.stringify(args[0]);
+  const error = args.length > 1 && args[1] != null
+    ? (typeof args[1] === "string" ? args[1] : JSON.stringify(args[1]))
+    : "unknown";
+  failed++;
+  const fullName = currentSuite() ? `${currentSuite()} > ${name}` : name;
+  errors.push(`FAIL: ${fullName}\n  ${error}`);
+  process.stdout.write("F");
+});
+
+K.registerNative("push-suite", (args) => {
+  const name = typeof args[0] === "string" ? args[0] : String(args[0]);
+  suiteStack.push(name);
+  return null;
+});
+
+K.registerNative("pop-suite", (_args) => {
+  suiteStack.pop();
+  return null;
+});
+
+console.log(`=== SX OCaml→JS Engine Test Runner ===`);
+console.log(`Engine: ${K.engine()}`);
+console.log(`Mode: ${full ? "full" : "standard"}`);
+console.log("");
+
+// Load a .sx file by reading it from disk and evaluating via loadSource
+function loadFile(filePath) {
+  const src = fs.readFileSync(filePath, "utf8");
+  return K.loadSource(src);
+}
+
+// Test files
+const specDir = path.join(__dirname, "../../../spec");
+const testDir = path.join(specDir, "tests");
+
+const standardTests = [
+  "test-framework.sx",
+  "test-eval.sx",
+  "test-parser.sx",
+  "test-primitives.sx",
+  "test-collections.sx",
+  "test-closures.sx",
+  "test-defcomp.sx",
+  "test-macros.sx",
+  "test-errors.sx",
+  "test-render.sx",
+  "test-tco.sx",
+  "test-scope.sx",
+  "test-cek.sx",
+  "test-advanced.sx",
+];
+
+const fullOnlyTests = [
+  "test-freeze.sx",
+  "test-continuations.sx",
+  "test-continuations-advanced.sx",
+  "test-cek-advanced.sx",
+  "test-signals-advanced.sx",
+  "test-render-advanced.sx",
+  "test-integration.sx",
+  "test-strict.sx",
+  "test-types.sx",
+];
+
+const testFiles = full ? [...standardTests, ...fullOnlyTests] : standardTests;
+
+for (const file of testFiles) {
+  const filePath = path.join(testDir, file);
+  if (!fs.existsSync(filePath)) {
+    console.log(`\nSkipping ${file} (not found)`);
+    continue;
+  }
+
+  const label = file.replace(".sx", "").replace("test-", "");
+  process.stdout.write(`\n[${label}] `);
+
+  const result = loadFile(filePath);
+  if (typeof result === "string" && result.startsWith("Error:")) {
+    console.log(`\n  LOAD ERROR: ${result}`);
+    failed++;
+    errors.push(`LOAD ERROR: ${file}\n  ${result}`);
+  }
+}
+
+console.log("\n");
+
+if (errors.length > 0) {
+  console.log(`--- Failures (${errors.length}) ---`);
+  for (const e of errors.slice(0, 20)) {
+    console.log(e);
+  }
+  if (errors.length > 20) {
+    console.log(`... and ${errors.length - 20} more`);
+  }
+  console.log("");
+}
+
+console.log(`Results: ${passed} passed, ${failed} failed, ${passed + failed} total`);
+process.exit(failed > 0 ? 1 : 0);
--- a/hosts/ocaml/browser/run_tests_wasm.js
+++ b/hosts/ocaml/browser/run_tests_wasm.js
@@ -0,0 +1,146 @@
+#!/usr/bin/env node
+/**
+ * Test runner for the wasm_of_ocaml-compiled SX engine.
+ *
+ * Loads the OCaml CEK machine (compiled to WASM) and runs the spec test suite.
+ * Requires Node.js 22+ with --experimental-wasm-imported-strings flag.
+ *
+ * Usage:
+ *   node --experimental-wasm-imported-strings hosts/ocaml/browser/run_tests_wasm.js
+ *   node --experimental-wasm-imported-strings hosts/ocaml/browser/run_tests_wasm.js --full
+ */
+
+const fs = require("fs");
+const path = require("path");
+
+const wasmDir = path.join(__dirname, "../_build/default/browser");
+const loaderPath = path.join(wasmDir, "sx_browser.bc.wasm.js");
+
+if (!fs.existsSync(loaderPath)) {
+  console.error("Build first: cd hosts/ocaml && eval $(opam env) && dune build browser/sx_browser.bc.wasm.js");
+  process.exit(1);
+}
+
+// Set require.main.filename so the WASM loader can find .wasm assets
+if (!require.main) {
+  require.main = { filename: path.join(wasmDir, "test.js") };
+} else {
+  require.main.filename = path.join(wasmDir, "test.js");
+}
+
+require(loaderPath);
+
+const full = process.argv.includes("--full");
+
+// WASM loader is async — wait for SxKernel to be available
+setTimeout(() => {
+  const K = globalThis.SxKernel;
+  if (!K) {
+    console.error("SxKernel not available — WASM initialization failed");
+    process.exit(1);
+  }
+
+  let passed = 0;
+  let failed = 0;
+  let errors = [];
+  let suiteStack = [];
+
+  function currentSuite() {
+    return suiteStack.length > 0 ? suiteStack.join(" > ") : "";
+  }
+
+  // Register platform test functions
+  K.registerNative("report-pass", (args) => {
+    const name = typeof args[0] === "string" ? args[0] : JSON.stringify(args[0]);
+    passed++;
+    if (process.env.VERBOSE) {
+      console.log(`  PASS: ${currentSuite()} > ${name}`);
+    } else {
+      process.stdout.write(".");
+      if (passed % 80 === 0) process.stdout.write("\n");
+    }
+    return null;
+  });
+
+  K.registerNative("report-fail", (args) => {
+    const name = typeof args[0] === "string" ? args[0] : JSON.stringify(args[0]);
+    const error = args.length > 1 && args[1] != null
+      ? (typeof args[1] === "string" ? args[1] : JSON.stringify(args[1]))
+      : "unknown";
+    failed++;
+    const fullName = currentSuite() ? `${currentSuite()} > ${name}` : name;
+    errors.push(`FAIL: ${fullName}\n  ${error}`);
+    process.stdout.write("F");
+  });
+
+  K.registerNative("push-suite", (args) => {
+    const name = typeof args[0] === "string" ? args[0] : String(args[0]);
+    suiteStack.push(name);
+    return null;
+  });
+
+  K.registerNative("pop-suite", (_args) => {
+    suiteStack.pop();
+    return null;
+  });
+
+  console.log(`=== SX OCaml→WASM Engine Test Runner ===`);
+  console.log(`Engine: ${K.engine()}`);
+  console.log(`Mode: ${full ? "full" : "standard"}`);
+  console.log("");
+
+  const specDir = path.join(__dirname, "../../../spec");
+  const testDir = path.join(specDir, "tests");
+
+  const standardTests = [
+    "test-framework.sx", "test-eval.sx", "test-parser.sx",
+    "test-primitives.sx", "test-collections.sx", "test-closures.sx",
+    "test-defcomp.sx", "test-macros.sx", "test-errors.sx",
+    "test-render.sx", "test-tco.sx", "test-scope.sx",
+    "test-cek.sx", "test-advanced.sx",
+  ];
+
+  const fullOnlyTests = [
+    "test-freeze.sx", "test-continuations.sx",
+    "test-continuations-advanced.sx", "test-cek-advanced.sx",
+    "test-signals-advanced.sx", "test-render-advanced.sx",
+    "test-integration.sx", "test-strict.sx", "test-types.sx",
+  ];
+
+  const testFiles = full ? [...standardTests, ...fullOnlyTests] : standardTests;
+
+  for (const file of testFiles) {
+    const filePath = path.join(testDir, file);
+    if (!fs.existsSync(filePath)) {
+      console.log(`\nSkipping ${file} (not found)`);
+      continue;
+    }
+
+    const label = file.replace(".sx", "").replace("test-", "");
+    process.stdout.write(`\n[${label}] `);
+
+    const src = fs.readFileSync(filePath, "utf8");
+    const result = K.loadSource(src);
+    if (typeof result === "string" && result.startsWith("Error:")) {
+      console.log(`\n  LOAD ERROR: ${result}`);
+      failed++;
+      errors.push(`LOAD ERROR: ${file}\n  ${result}`);
+    }
+  }
+
+  console.log("\n");
+
+  if (errors.length > 0) {
+    console.log(`--- Failures (${errors.length}) ---`);
+    for (const e of errors.slice(0, 20)) {
+      console.log(e);
+    }
+    if (errors.length > 20) {
+      console.log(`... and ${errors.length - 20} more`);
+    }
+    console.log("");
+  }
+
+  console.log(`Results: ${passed} passed, ${failed} failed, ${passed + failed} total`);
+  process.exit(failed > 0 ? 1 : 0);
+}, 1000);
--- a/hosts/ocaml/browser/sx-platform.js
+++ b/hosts/ocaml/browser/sx-platform.js
@@ -0,0 +1,676 @@
+/**
+ * sx-platform.js — Thin JS platform layer for the OCaml SX WASM engine.
+ *
+ * This file provides browser-native primitives (DOM, fetch, timers, etc.)
+ * to the WASM-compiled OCaml CEK machine. It:
+ *   1. Loads the WASM module (SxKernel)
+ *   2. Registers ~80 native browser functions via registerNative
+ *   3. Loads web adapters (.sx files) into the engine
+ *   4. Exports the public Sx API
+ *
+ * Both wasm_of_ocaml and js_of_ocaml targets bind to this same layer.
+ */
+
+(function(global) {
+  "use strict";
+
+  function initPlatform() {
+  var K = global.SxKernel;
+  if (!K) {
+    // WASM loader is async — wait and retry
+    setTimeout(initPlatform, 20);
+    return;
+  }
+
+  var _hasDom = typeof document !== "undefined";
+  var NIL = null;
+  var SVG_NS = "http://www.w3.org/2000/svg";
+
+  // =========================================================================
+  // Helper: wrap SX lambda for use as JS callback
+  // =========================================================================
+
+  function wrapLambda(fn) {
+    // For now, SX lambdas from registerNative are opaque — we can't call them
+    // directly from JS. They need to go through the engine.
+    // TODO: add callLambda API to SxKernel
+    return fn;
+  }
+
+  // =========================================================================
+  // 1. DOM Creation & Manipulation
+  // =========================================================================
+
+  K.registerNative("dom-create-element", function(args) {
+    if (!_hasDom) return NIL;
+    var tag = args[0], ns = args[1];
+    if (ns && ns !== NIL) return document.createElementNS(ns, tag);
+    return document.createElement(tag);
+  });
+
+  K.registerNative("create-text-node", function(args) {
+    return _hasDom ? document.createTextNode(args[0] || "") : NIL;
+  });
+
+  K.registerNative("create-comment", function(args) {
+    return _hasDom ? document.createComment(args[0] || "") : NIL;
+  });
+
+  K.registerNative("create-fragment", function(_args) {
+    return _hasDom ? document.createDocumentFragment() : NIL;
+  });
+
+  K.registerNative("dom-clone", function(args) {
+    var node = args[0];
+    return node && node.cloneNode ? node.cloneNode(true) : node;
+  });
+
+  K.registerNative("dom-parse-html", function(args) {
+    if (!_hasDom) return NIL;
+    var tpl = document.createElement("template");
+    tpl.innerHTML = args[0] || "";
+    return tpl.content;
+  });
+
+  K.registerNative("dom-parse-html-document", function(args) {
+    if (!_hasDom) return NIL;
+    var parser = new DOMParser();
+    return parser.parseFromString(args[0] || "", "text/html");
+  });
+
+  // =========================================================================
+  // 2. DOM Queries
+  // =========================================================================
+
+  K.registerNative("dom-query", function(args) {
+    return _hasDom ? document.querySelector(args[0]) || NIL : NIL;
+  });
+
+  K.registerNative("dom-query-all", function(args) {
+    var root = args[0] || (_hasDom ? document : null);
+    if (!root || !root.querySelectorAll) return [];
+    return Array.prototype.slice.call(root.querySelectorAll(args[1] || args[0]));
+  });
+
+  K.registerNative("dom-query-by-id", function(args) {
+    return _hasDom ? document.getElementById(args[0]) || NIL : NIL;
+  });
+
+  K.registerNative("dom-body", function(_args) {
+    return _hasDom ? document.body : NIL;
+  });
+
+  K.registerNative("dom-ensure-element", function(args) {
+    if (!_hasDom) return NIL;
+    var sel = args[0];
+    var el = document.querySelector(sel);
+    if (el) return el;
+    if (sel.charAt(0) === "#") {
+      el = document.createElement("div");
+      el.id = sel.slice(1);
+      document.body.appendChild(el);
+      return el;
+    }
+    return NIL;
+  });
+
+  // =========================================================================
+  // 3. DOM Attributes
+  // =========================================================================
+
+  K.registerNative("dom-get-attr", function(args) {
+    var el = args[0], name = args[1];
+    if (!el || !el.getAttribute) return NIL;
+    var v = el.getAttribute(name);
+    return v === null ? NIL : v;
+  });
+
+  K.registerNative("dom-set-attr", function(args) {
+    var el = args[0], name = args[1], val = args[2];
+    if (el && el.setAttribute) el.setAttribute(name, val);
+    return NIL;
+  });
+
+  K.registerNative("dom-remove-attr", function(args) {
+    if (args[0] && args[0].removeAttribute) args[0].removeAttribute(args[1]);
+    return NIL;
+  });
+
+  K.registerNative("dom-has-attr?", function(args) {
+    return !!(args[0] && args[0].hasAttribute && args[0].hasAttribute(args[1]));
+  });
+
+  K.registerNative("dom-attr-list", function(args) {
+    var el = args[0];
+    if (!el || !el.attributes) return [];
+    var r = [];
+    for (var i = 0; i < el.attributes.length; i++) {
+      r.push([el.attributes[i].name, el.attributes[i].value]);
+    }
+    return r;
+  });
+
+  // =========================================================================
+  // 4. DOM Content
+  // =========================================================================
+
+  K.registerNative("dom-text-content", function(args) {
+    var el = args[0];
+    return el ? el.textContent || el.nodeValue || "" : "";
+  });
+
+  K.registerNative("dom-set-text-content", function(args) {
+    var el = args[0], s = args[1];
+    if (el) {
+      if (el.nodeType === 3 || el.nodeType === 8) el.nodeValue = s;
+      else el.textContent = s;
+    }
+    return NIL;
+  });
+
+  K.registerNative("dom-inner-html", function(args) {
+    return args[0] && args[0].innerHTML != null ? args[0].innerHTML : "";
+  });
+
+  K.registerNative("dom-set-inner-html", function(args) {
+    if (args[0]) args[0].innerHTML = args[1] || "";
+    return NIL;
+  });
+
+  K.registerNative("dom-insert-adjacent-html", function(args) {
+    var el = args[0], pos = args[1], html = args[2];
+    if (el && el.insertAdjacentHTML) el.insertAdjacentHTML(pos, html);
+    return NIL;
+  });
+
+  K.registerNative("dom-body-inner-html", function(args) {
+    var doc = args[0];
+    return doc && doc.body ? doc.body.innerHTML : "";
+  });
+
+  // =========================================================================
+  // 5. DOM Structure & Navigation
+  // =========================================================================
+
+  K.registerNative("dom-parent", function(args) { return args[0] ? args[0].parentNode || NIL : NIL; });
+  K.registerNative("dom-first-child", function(args) { return args[0] ? args[0].firstChild || NIL : NIL; });
+  K.registerNative("dom-next-sibling", function(args) { return args[0] ? args[0].nextSibling || NIL : NIL; });
+  K.registerNative("dom-id", function(args) { return args[0] && args[0].id ? args[0].id : NIL; });
+  K.registerNative("dom-node-type", function(args) { return args[0] ? args[0].nodeType : 0; });
+  K.registerNative("dom-node-name", function(args) { return args[0] ? args[0].nodeName : ""; });
+  K.registerNative("dom-tag-name", function(args) { return args[0] && args[0].tagName ? args[0].tagName : ""; });
+
+  K.registerNative("dom-child-list", function(args) {
+    var el = args[0];
+    if (!el || !el.childNodes) return [];
+    return Array.prototype.slice.call(el.childNodes);
+  });
+
+  K.registerNative("dom-child-nodes", function(args) {
+    var el = args[0];
+    if (!el || !el.childNodes) return [];
+    return Array.prototype.slice.call(el.childNodes);
+  });
+
+  // =========================================================================
+  // 6. DOM Insertion & Removal
+  // =========================================================================
+
+  K.registerNative("dom-append", function(args) {
+    var parent = args[0], child = args[1];
+    if (parent && child) parent.appendChild(child);
+    return NIL;
+  });
+
+  K.registerNative("dom-prepend", function(args) {
+    var parent = args[0], child = args[1];
+    if (parent && child) parent.insertBefore(child, parent.firstChild);
+    return NIL;
+  });
+
+  K.registerNative("dom-insert-before", function(args) {
+    var parent = args[0], node = args[1], ref = args[2];
+    if (parent && node) parent.insertBefore(node, ref || null);
+    return NIL;
+  });
+
+  K.registerNative("dom-insert-after", function(args) {
+    var ref = args[0], node = args[1];
+    if (ref && ref.parentNode && node) {
+      ref.parentNode.insertBefore(node, ref.nextSibling);
+    }
+    return NIL;
+  });
+
+  K.registerNative("dom-remove", function(args) {
+    var node = args[0];
+    if (node && node.parentNode) node.parentNode.removeChild(node);
+    return NIL;
+  });
+
+  K.registerNative("dom-remove-child", function(args) {
+    var parent = args[0], child = args[1];
+    if (parent && child && child.parentNode === parent) parent.removeChild(child);
+    return NIL;
+  });
+
+  K.registerNative("dom-replace-child", function(args) {
+    var parent = args[0], newC = args[1], oldC = args[2];
+    if (parent && newC && oldC) parent.replaceChild(newC, oldC);
+    return NIL;
+  });
+
+  K.registerNative("dom-remove-children-after", function(args) {
+    var marker = args[0];
+    if (!marker || !marker.parentNode) return NIL;
+    var parent = marker.parentNode;
+    while (marker.nextSibling) parent.removeChild(marker.nextSibling);
+    return NIL;
+  });
+
+  K.registerNative("dom-append-to-head", function(args) {
+    if (_hasDom && args[0]) document.head.appendChild(args[0]);
+    return NIL;
+  });
+
+  // =========================================================================
+  // 7. DOM Type Checks
+  // =========================================================================
+
+  K.registerNative("dom-is-fragment?", function(args) { return args[0] ? args[0].nodeType === 11 : false; });
+  K.registerNative("dom-is-child-of?", function(args) { return !!(args[1] && args[0] && args[0].parentNode === args[1]); });
+  K.registerNative("dom-is-active-element?", function(args) { return _hasDom && args[0] === document.activeElement; });
+  K.registerNative("dom-is-input-element?", function(args) {
+    if (!args[0] || !args[0].tagName) return false;
+    var t = args[0].tagName;
+    return t === "INPUT" || t === "TEXTAREA" || t === "SELECT";
+  });
+
+  // =========================================================================
+  // 8. DOM Styles & Classes
+  // =========================================================================
+
+  K.registerNative("dom-get-style", function(args) {
+    return args[0] && args[0].style ? args[0].style[args[1]] || "" : "";
+  });
+
+  K.registerNative("dom-set-style", function(args) {
+    if (args[0] && args[0].style) args[0].style[args[1]] = args[2];
+    return NIL;
+  });
+
+  K.registerNative("dom-add-class", function(args) {
+    if (args[0] && args[0].classList) args[0].classList.add(args[1]);
+    return NIL;
+  });
+
+  K.registerNative("dom-remove-class", function(args) {
+    if (args[0] && args[0].classList) args[0].classList.remove(args[1]);
+    return NIL;
+  });
+
+  K.registerNative("dom-has-class?", function(args) {
+    return !!(args[0] && args[0].classList && args[0].classList.contains(args[1]));
+  });
+
+  // =========================================================================
+  // 9. DOM Properties & Data
+  // =========================================================================
+
+  K.registerNative("dom-get-prop", function(args) { return args[0] ? args[0][args[1]] : NIL; });
+  K.registerNative("dom-set-prop", function(args) { if (args[0]) args[0][args[1]] = args[2]; return NIL; });
+
+  K.registerNative("dom-set-data", function(args) {
+    var el = args[0], key = args[1], val = args[2];
+    if (el) { if (!el._sxData) el._sxData = {}; el._sxData[key] = val; }
+    return NIL;
+  });
+
+  K.registerNative("dom-get-data", function(args) {
+    var el = args[0], key = args[1];
+    return (el && el._sxData) ? (el._sxData[key] != null ? el._sxData[key] : NIL) : NIL;
+  });
+
+  K.registerNative("dom-call-method", function(args) {
+    var obj = args[0], method = args[1];
+    var callArgs = args.slice(2);
+    if (obj && typeof obj[method] === "function") {
+      try { return obj[method].apply(obj, callArgs); }
+      catch(e) { return NIL; }
+    }
+    return NIL;
+  });
+
+  // =========================================================================
+  // 10. DOM Events
+  // =========================================================================
+
+  K.registerNative("dom-listen", function(args) {
+    var el = args[0], name = args[1], handler = args[2];
+    if (!_hasDom || !el) return function() {};
+
+    // handler is a wrapped SX lambda (JS function with __sx_handle).
+    // Wrap it to:
+    //   - Pass the event object as arg (or no args for 0-arity handlers)
+    //   - Catch errors from the CEK machine
+    var arity = K.fnArity(handler);
+    var wrapped;
+    if (arity === 0) {
+      wrapped = function(_e) {
+        try { K.callFn(handler, []); }
+        catch(err) { console.error("[sx] event handler error:", name, err); }
+      };
+    } else {
+      wrapped = function(e) {
+        try { K.callFn(handler, [e]); }
+        catch(err) { console.error("[sx] event handler error:", name, err); }
+      };
+    }
+    el.addEventListener(name, wrapped);
+    return function() { el.removeEventListener(name, wrapped); };
+  });
+
+  K.registerNative("dom-dispatch", function(args) {
+    if (!_hasDom || !args[0]) return false;
+    var evt = new CustomEvent(args[1], { bubbles: true, cancelable: true, detail: args[2] || {} });
+    return args[0].dispatchEvent(evt);
+  });
+
+  K.registerNative("event-detail", function(args) {
+    return (args[0] && args[0].detail != null) ? args[0].detail : NIL;
+  });
+
+  // =========================================================================
+  // 11. Browser Navigation & History
+  // =========================================================================
+
+  K.registerNative("browser-location-href", function(_args) {
+    return typeof location !== "undefined" ? location.href : "";
+  });
+
+  K.registerNative("browser-same-origin?", function(args) {
+    try { return new URL(args[0], location.href).origin === location.origin; }
+    catch (e) { return true; }
+  });
+
+  K.registerNative("browser-push-state", function(args) {
+    if (typeof history !== "undefined") {
+      try { history.pushState({ sxUrl: args[0], scrollY: typeof window !== "undefined" ? window.scrollY : 0 }, "", args[0]); }
+      catch (e) {}
+    }
+    return NIL;
+  });
+
+  K.registerNative("browser-replace-state", function(args) {
+    if (typeof history !== "undefined") {
+      try { history.replaceState({ sxUrl: args[0], scrollY: typeof window !== "undefined" ? window.scrollY : 0 }, "", args[0]); }
+      catch (e) {}
+    }
+    return NIL;
+  });
+
+  K.registerNative("browser-navigate", function(args) {
+    if (typeof location !== "undefined") location.assign(args[0]);
+    return NIL;
+  });
+
+  K.registerNative("browser-reload", function(_args) {
+    if (typeof location !== "undefined") location.reload();
+    return NIL;
+  });
+
+  K.registerNative("browser-scroll-to", function(args) {
+    if (typeof window !== "undefined") window.scrollTo(args[0] || 0, args[1] || 0);
+    return NIL;
+  });
+
+  K.registerNative("browser-media-matches?", function(args) {
+    if (typeof window === "undefined") return false;
+    return window.matchMedia(args[0]).matches;
+  });
+
+  K.registerNative("browser-confirm", function(args) {
+    if (typeof window === "undefined") return false;
+    return window.confirm(args[0]);
+  });
+
+  K.registerNative("browser-prompt", function(args) {
+    if (typeof window === "undefined") return NIL;
+    var r = window.prompt(args[0]);
+    return r === null ? NIL : r;
+  });
+
+  // =========================================================================
+  // 12. Timers
+  // =========================================================================
+
+  K.registerNative("set-timeout", function(args) {
+    var fn = args[0], ms = args[1] || 0;
+    var cb = (typeof fn === "function" && fn.__sx_handle != null)
+      ? function() { try { K.callFn(fn, []); } catch(e) { console.error("[sx] timeout error:", e); } }
+      : fn;
+    return setTimeout(cb, ms);
+  });
+
+  K.registerNative("set-interval", function(args) {
+    var fn = args[0], ms = args[1] || 1000;
+    var cb = (typeof fn === "function" && fn.__sx_handle != null)
+      ? function() { try { K.callFn(fn, []); } catch(e) { console.error("[sx] interval error:", e); } }
+      : fn;
+    return setInterval(cb, ms);
+  });
+
+  K.registerNative("clear-timeout", function(args) { clearTimeout(args[0]); return NIL; });
+  K.registerNative("clear-interval", function(args) { clearInterval(args[0]); return NIL; });
+  K.registerNative("now-ms", function(_args) {
+    return (typeof performance !== "undefined") ? performance.now() : Date.now();
+  });
+
+  K.registerNative("request-animation-frame", function(args) {
+    var fn = args[0];
+    var cb = (typeof fn === "function" && fn.__sx_handle != null)
+      ? function() { try { K.callFn(fn, []); } catch(e) { console.error("[sx] raf error:", e); } }
+      : fn;
+    if (typeof requestAnimationFrame !== "undefined") requestAnimationFrame(cb);
+    else setTimeout(cb, 16);
+    return NIL;
+  });
+
+  // =========================================================================
+  // 13. Promises
+  // =========================================================================
+
+  K.registerNative("promise-resolve", function(args) { return Promise.resolve(args[0]); });
+
+  K.registerNative("promise-then", function(args) {
+    var p = args[0];
+    if (!p || !p.then) return p;
+    var onResolve = function(v) { return K.callFn(args[1], [v]); };
+    var onReject = args[2] ? function(e) { return K.callFn(args[2], [e]); } : undefined;
+    return onReject ? p.then(onResolve, onReject) : p.then(onResolve);
+  });
+
+  K.registerNative("promise-catch", function(args) {
+    if (!args[0] || !args[0].catch) return args[0];
+    return args[0].catch(function(e) { return K.callFn(args[1], [e]); });
+  });
+
+  K.registerNative("promise-delayed", function(args) {
+    return new Promise(function(resolve) {
+      setTimeout(function() { resolve(args[1]); }, args[0]);
+    });
+  });
+
+  // =========================================================================
+  // 14. Abort Controllers
+  // =========================================================================
+
+  var _controllers = typeof WeakMap !== "undefined" ? new WeakMap() : null;
+  var _targetControllers = typeof WeakMap !== "undefined" ? new WeakMap() : null;
+
+  K.registerNative("new-abort-controller", function(_args) {
+    return typeof AbortController !== "undefined" ? new AbortController() : { signal: null, abort: function() {} };
+  });
+
+  K.registerNative("abort-previous", function(args) {
+    if (_controllers) { var prev = _controllers.get(args[0]); if (prev) prev.abort(); }
+    return NIL;
+  });
+
+  K.registerNative("track-controller", function(args) {
+    if (_controllers) _controllers.set(args[0], args[1]);
+    return NIL;
+  });
+
+  K.registerNative("abort-previous-target", function(args) {
+    if (_targetControllers) { var prev = _targetControllers.get(args[0]); if (prev) prev.abort(); }
+    return NIL;
+  });
+
+  K.registerNative("track-controller-target", function(args) {
+    if (_targetControllers) _targetControllers.set(args[0], args[1]);
+    return NIL;
+  });
+
+  K.registerNative("controller-signal", function(args) { return args[0] ? args[0].signal : NIL; });
+  K.registerNative("is-abort-error", function(args) { return args[0] && args[0].name === "AbortError"; });
+
+  // =========================================================================
+  // 15. Fetch
+  // =========================================================================
+
+  K.registerNative("fetch-request", function(args) {
+    var config = args[0], successFn = args[1], errorFn = args[2];
+    var opts = { method: config.method, headers: config.headers };
+    if (config.signal) opts.signal = config.signal;
+    if (config.body && config.method !== "GET") opts.body = config.body;
+    if (config["cross-origin"]) opts.credentials = "include";
+
+    return fetch(config.url, opts).then(function(resp) {
+      return resp.text().then(function(text) {
+        var getHeader = function(name) {
+          var v = resp.headers.get(name);
+          return v === null ? NIL : v;
+        };
+        return K.callFn(successFn, [resp.ok, resp.status, getHeader, text]);
+      });
+    }).catch(function(err) {
+      return K.callFn(errorFn, [err]);
+    });
+  });
+
+  K.registerNative("csrf-token", function(_args) {
+    if (!_hasDom) return NIL;
+    var m = document.querySelector('meta[name="csrf-token"]');
+    return m ? m.getAttribute("content") : NIL;
+  });
+
+  K.registerNative("is-cross-origin", function(args) {
+    try {
+      var h = new URL(args[0], location.href).hostname;
+      return h !== location.hostname &&
+        (h.indexOf(".rose-ash.com") >= 0 || h.indexOf(".localhost") >= 0);
+    } catch (e) { return false; }
+  });
+
+  // =========================================================================
+  // 16. localStorage
+  // =========================================================================
+
+  K.registerNative("local-storage-get", function(args) {
+    try { var v = localStorage.getItem(args[0]); return v === null ? NIL : v; }
+    catch(e) { return NIL; }
+  });
+
+  K.registerNative("local-storage-set", function(args) {
+    try { localStorage.setItem(args[0], args[1]); } catch(e) {}
+    return NIL;
+  });
+
+  K.registerNative("local-storage-remove", function(args) {
+    try { localStorage.removeItem(args[0]); } catch(e) {}
+    return NIL;
+  });
+
+  // =========================================================================
+  // 17. Document Head & Title
+  // =========================================================================
+
+  K.registerNative("set-document-title", function(args) {
+    if (_hasDom) document.title = args[0] || "";
+    return NIL;
+  });
+
+  K.registerNative("remove-head-element", function(args) {
+    if (_hasDom) {
+      var el = document.head.querySelector(args[0]);
+      if (el) el.remove();
+    }
+    return NIL;
+  });
+
+  // =========================================================================
+  // 18. Logging
+  // =========================================================================
+
+  K.registerNative("log-info", function(args) { console.log("[sx]", args[0]); return NIL; });
+  K.registerNative("log-warn", function(args) { console.warn("[sx]", args[0]); return NIL; });
+  K.registerNative("log-error", function(args) { console.error("[sx]", args[0]); return NIL; });
+
+  // =========================================================================
+  // 19. JSON
+  // =========================================================================
+
+  K.registerNative("json-parse", function(args) {
+    try { return JSON.parse(args[0]); } catch(e) { return {}; }
+  });
+
+  K.registerNative("try-parse-json", function(args) {
+    try { return JSON.parse(args[0]); } catch(e) { return NIL; }
+  });
+
+  // =========================================================================
+  // 20. Processing markers
+  // =========================================================================
+
+  K.registerNative("mark-processed!", function(args) {
+    var el = args[0], key = args[1] || "sx";
+    if (el) { if (!el._sxProcessed) el._sxProcessed = {}; el._sxProcessed[key] = true; }
+    return NIL;
+  });
+
+  K.registerNative("is-processed?", function(args) {
+    var el = args[0], key = args[1] || "sx";
+    return !!(el && el._sxProcessed && el._sxProcessed[key]);
+  });
+
+  // =========================================================================
+  // Public Sx API (wraps SxKernel for compatibility with existing code)
+  // =========================================================================
+
+  var Sx = {
+    // Core (delegated to WASM engine)
+    parse: K.parse,
+    eval: K.eval,
+    evalExpr: K.evalExpr,
+    load: K.load,
+    loadSource: K.loadSource,
+    renderToHtml: K.renderToHtml,
+    typeOf: K.typeOf,
+    inspect: K.inspect,
+    engine: K.engine,
+
+    // Will be populated after web adapters load:
+    // mount, hydrate, processElements, etc.
+  };
+
+  global.Sx = Sx;
+  global.SxKernel = K;  // Keep kernel available for direct access
+
+  console.log("[sx-platform] registered, engine:", K.engine());
+
+  } // end initPlatform
+
+  initPlatform();
+
+})(typeof globalThis !== "undefined" ? globalThis : this);
--- a/hosts/ocaml/browser/sx_browser.ml
+++ b/hosts/ocaml/browser/sx_browser.ml
@@ -0,0 +1,946 @@
+(** sx_browser.ml — OCaml SX engine compiled to WASM/JS for browser use.
+
+    Exposes the CEK machine, parser, and primitives as a global [Sx] object
+    that the thin JS platform layer binds to. *)
+
+open Js_of_ocaml
+open Sx_types
+
+(* ================================================================== *)
+(* Value conversion: OCaml <-> JS                                      *)
+(* ================================================================== *)
+
+(* ------------------------------------------------------------------ *)
+(* Opaque value handle table                                           *)
+(*                                                                     *)
+(* Non-primitive SX values (lambdas, components, signals, etc.) are    *)
+(* stored in a handle table and represented on the JS side as objects  *)
+(* with an __sx_handle integer key.  This preserves identity across    *)
+(* the JS↔OCaml boundary — the same handle always resolves to the     *)
+(* same OCaml value.                                                   *)
+(*                                                                     *)
+(* Callable values (Lambda, NativeFn, Continuation) are additionally  *)
+(* wrapped as JS functions so they can be used directly as event       *)
+(* listeners, setTimeout callbacks, etc.                               *)
+(* ------------------------------------------------------------------ *)
+
+let _next_handle = ref 0
+let _handle_table : (int, value) Hashtbl.t = Hashtbl.create 256
+
+(** Store a value in the handle table, return its handle id. *)
+let alloc_handle (v : value) : int =
+  let id = !_next_handle in
+  incr _next_handle;
+  Hashtbl.replace _handle_table id v;
+  id
+
+(** Look up a value by handle. *)
+let get_handle (id : int) : value =
+  match Hashtbl.find_opt _handle_table id with
+  | Some v -> v
+  | None -> raise (Eval_error (Printf.sprintf "Invalid SX handle: %d" id))
+
+(** Late-bound reference to global env (set after global_env is created). *)
+let _global_env_ref : env option ref = ref None
+let get_global_env () = match !_global_env_ref with
+  | Some e -> e | None -> raise (Eval_error "Global env not initialized")
+
+(** Call an SX callable through the CEK machine.
+    Constructs (fn arg1 arg2 ...) and evaluates it. *)
+let call_sx_fn (fn : value) (args : value list) : value =
+  Sx_ref.eval_expr (List (fn :: args)) (Env (get_global_env ()))
+
+(** Convert an OCaml SX value to a JS representation.
+    Primitive types map directly.
+    Callable values become JS functions (with __sx_handle).
+    Other compound types become tagged objects (with __sx_handle). *)
+let rec value_to_js (v : value) : Js.Unsafe.any =
+  match v with
+  | Nil -> Js.Unsafe.inject Js.null
+  | Bool b -> Js.Unsafe.inject (Js.bool b)
+  | Number n -> Js.Unsafe.inject (Js.number_of_float n)
+  | String s -> Js.Unsafe.inject (Js.string s)
+  | Symbol s ->
+    let obj = Js.Unsafe.obj [| ("_type", Js.Unsafe.inject (Js.string "symbol"));
+                                ("name", Js.Unsafe.inject (Js.string s)) |] in
+    Js.Unsafe.inject obj
+  | Keyword k ->
+    let obj = Js.Unsafe.obj [| ("_type", Js.Unsafe.inject (Js.string "keyword"));
+                                ("name", Js.Unsafe.inject (Js.string k)) |] in
+    Js.Unsafe.inject obj
+  | List items ->
+    let arr = items |> List.map value_to_js |> Array.of_list in
+    let js_arr = Js.array arr in
+    let obj = Js.Unsafe.obj [| ("_type", Js.Unsafe.inject (Js.string "list"));
+                                ("items", Js.Unsafe.inject js_arr) |] in
+    Js.Unsafe.inject obj
+  | ListRef r ->
+    let arr = !r |> List.map value_to_js |> Array.of_list in
+    let js_arr = Js.array arr in
+    let obj = Js.Unsafe.obj [| ("_type", Js.Unsafe.inject (Js.string "list"));
+                                ("items", Js.Unsafe.inject js_arr) |] in
+    Js.Unsafe.inject obj
+  | Dict d ->
+    let obj = Js.Unsafe.obj [||] in
+    Js.Unsafe.set obj (Js.string "_type") (Js.string "dict");
+    Hashtbl.iter (fun k v ->
+      Js.Unsafe.set obj (Js.string k) (value_to_js v)
+    ) d;
+    Js.Unsafe.inject obj
+  | RawHTML s -> Js.Unsafe.inject (Js.string s)
+  (* Callable values: wrap as JS functions *)
+  | Lambda _ | NativeFn _ | Continuation _ ->
+    let handle = alloc_handle v in
+    (* Create a JS function that calls back into the CEK machine.
+       Use _tagFn helper (registered on globalThis) to create a function
+       with __sx_handle and _type properties that survive js_of_ocaml
+       return-value wrapping. *)
+    let inner = Js.wrap_callback (fun args_js ->
+      try
+        let arg = js_to_value args_js in
+        let args = match arg with Nil -> [] | _ -> [arg] in
+        let result = call_sx_fn v args in
+        value_to_js result
+      with Eval_error msg ->
+        ignore (Js.Unsafe.meth_call (Js.Unsafe.get Js.Unsafe.global (Js.string "console"))
+          "error" [| Js.Unsafe.inject (Js.string (Printf.sprintf "[sx] callback error: %s" msg)) |]);
+        Js.Unsafe.inject Js.null
+    ) in
+    let tag_fn = Js.Unsafe.get Js.Unsafe.global (Js.string "__sxTagFn") in
+    Js.Unsafe.fun_call tag_fn [|
+      Js.Unsafe.inject inner;
+      Js.Unsafe.inject handle;
+      Js.Unsafe.inject (Js.string (type_of v))
+    |]
+  (* Non-callable compound values: tagged objects with handle *)
+  | Component c ->
+    let handle = alloc_handle v in
+    let obj = Js.Unsafe.obj [| ("_type", Js.Unsafe.inject (Js.string "component"));
+                                ("name", Js.Unsafe.inject (Js.string c.c_name));
+                                ("__sx_handle", Js.Unsafe.inject handle) |] in
+    Js.Unsafe.inject obj
+  | Island i ->
+    let handle = alloc_handle v in
+    let obj = Js.Unsafe.obj [| ("_type", Js.Unsafe.inject (Js.string "island"));
+                                ("name", Js.Unsafe.inject (Js.string i.i_name));
+                                ("__sx_handle", Js.Unsafe.inject handle) |] in
+    Js.Unsafe.inject obj
+  | Signal _ ->
+    let handle = alloc_handle v in
+    let obj = Js.Unsafe.obj [| ("_type", Js.Unsafe.inject (Js.string "signal"));
+                                ("__sx_handle", Js.Unsafe.inject handle) |] in
+    Js.Unsafe.inject obj
+  | _ ->
+    let handle = alloc_handle v in
+    let obj = Js.Unsafe.obj [| ("_type", Js.Unsafe.inject (Js.string (type_of v)));
+                                ("__sx_handle", Js.Unsafe.inject handle) |] in
+    Js.Unsafe.inject obj
+
+(** Convert a JS value back to an OCaml SX value. *)
+and js_to_value (js : Js.Unsafe.any) : value =
+  (* Check null/undefined *)
+  if Js.Unsafe.equals js Js.null || Js.Unsafe.equals js Js.undefined then
+    Nil
+  else
+    let ty = Js.to_string (Js.typeof js) in
+    match ty with
+    | "number" ->
+      Number (Js.float_of_number (Js.Unsafe.coerce js))
+    | "boolean" ->
+      Bool (Js.to_bool (Js.Unsafe.coerce js))
+    | "string" ->
+      String (Js.to_string (Js.Unsafe.coerce js))
+    | "function" ->
+      (* Check for __sx_handle — this is a wrapped SX callable *)
+      let handle_field = Js.Unsafe.get js (Js.string "__sx_handle") in
+      if not (Js.Unsafe.equals handle_field Js.undefined) then
+        let id = Js.float_of_number (Js.Unsafe.coerce handle_field) |> int_of_float in
+        get_handle id
+      else
+        (* Plain JS function — wrap as NativeFn *)
+        NativeFn ("js-callback", fun args ->
+          let js_args = args |> List.map value_to_js |> Array.of_list in
+          let result = Js.Unsafe.fun_call js
+            (Array.map (fun a -> a) js_args) in
+          js_to_value result)
+    | "object" ->
+      (* Check for __sx_handle — this is a wrapped SX value *)
+      let handle_field = Js.Unsafe.get js (Js.string "__sx_handle") in
+      if not (Js.Unsafe.equals handle_field Js.undefined) then begin
+        let id = Js.float_of_number (Js.Unsafe.coerce handle_field) |> int_of_float in
+        get_handle id
+      end else begin
+        (* Check for _type tag *)
+        let type_field = Js.Unsafe.get js (Js.string "_type") in
+        if Js.Unsafe.equals type_field Js.undefined then begin
+          (* Check if it's an array *)
+          let is_arr = Js.to_bool (Js.Unsafe.global##._Array##isArray js) in
+          if is_arr then begin
+            let len_js = Js.Unsafe.get js (Js.string "length") in
+            let n = Js.float_of_number (Js.Unsafe.coerce len_js) |> int_of_float in
+            let items = List.init n (fun i ->
+              js_to_value (Js.array_get (Js.Unsafe.coerce js) i
+                           |> Js.Optdef.to_option |> Option.get)
+            ) in
+            List items
+          end else begin
+            (* Plain JS object — convert to dict *)
+            let d = Hashtbl.create 8 in
+            let keys = Js.Unsafe.global##._Object##keys js in
+            let len = keys##.length in
+            for i = 0 to len - 1 do
+              let k = Js.to_string (Js.array_get keys i |> Js.Optdef.to_option |> Option.get) in
+              let v = Js.Unsafe.get js (Js.string k) in
+              Hashtbl.replace d k (js_to_value v)
+            done;
+            Dict d
+          end
+        end else begin
+          let tag = Js.to_string (Js.Unsafe.coerce type_field) in
+          match tag with
+          | "symbol" ->
+            Symbol (Js.to_string (Js.Unsafe.get js (Js.string "name")))
+          | "keyword" ->
+            Keyword (Js.to_string (Js.Unsafe.get js (Js.string "name")))
+          | "list" ->
+            let items_js = Js.Unsafe.get js (Js.string "items") in
+            let len = Js.Unsafe.get items_js (Js.string "length") in
+            let n = Js.float_of_number (Js.Unsafe.coerce len) |> int_of_float in
+            let items = List.init n (fun i ->
+              js_to_value (Js.array_get (Js.Unsafe.coerce items_js) i
+                           |> Js.Optdef.to_option |> Option.get)
+            ) in
+            List items
+          | "dict" ->
+            let d = Hashtbl.create 8 in
+            let keys = Js.Unsafe.global##._Object##keys js in
+            let len = keys##.length in
+            for i = 0 to len - 1 do
+              let k = Js.to_string (Js.array_get keys i |> Js.Optdef.to_option |> Option.get) in
+              if k <> "_type" then begin
+                let v = Js.Unsafe.get js (Js.string k) in
+                Hashtbl.replace d k (js_to_value v)
+              end
+            done;
+            Dict d
+          | _ -> Nil
+        end
+      end
+    | _ -> Nil
+
+(* ================================================================== *)
+(* Global environment                                                  *)
+(* ================================================================== *)
+
+let global_env = make_env ()
+let () = _global_env_ref := Some global_env
+
+(* Render mode flag — set true during renderToHtml/loadSource calls
+   that should dispatch HTML tags to the renderer. *)
+let _sx_render_mode = ref false
+
+(* Register JS helpers.
+   __sxTagFn: tag a function with __sx_handle and _type properties.
+   __sxR: side-channel for return values (bypasses Js.wrap_callback
+          which strips custom properties from function objects). *)
+let () =
+  let tag_fn = Js.Unsafe.pure_js_expr
+    "(function(fn, handle, type) { fn.__sx_handle = handle; fn._type = type; return fn; })" in
+  Js.Unsafe.set Js.Unsafe.global (Js.string "__sxTagFn") tag_fn
+
+(** Store a value in the side-channel and return a sentinel.
+    The JS wrapper picks up __sxR instead of the return value. *)
+let return_via_side_channel (v : Js.Unsafe.any) : Js.Unsafe.any =
+  Js.Unsafe.set Js.Unsafe.global (Js.string "__sxR") v;
+  v
+
+(* ================================================================== *)
+(* Core API functions                                                  *)
+(* ================================================================== *)
+
+(** Parse SX source string into a list of values. *)
+let api_parse src_js =
+  let src = Js.to_string src_js in
+  try
+    let values = Sx_parser.parse_all src in
+    let arr = values |> List.map value_to_js |> Array.of_list in
+    Js.Unsafe.inject (Js.array arr)
+  with Parse_error msg ->
+    Js.Unsafe.inject (Js.string ("Parse error: " ^ msg))
+
+(** Serialize an SX value to source text. *)
+let api_stringify v_js =
+  let v = js_to_value v_js in
+  Js.Unsafe.inject (Js.string (inspect v))
+
+(** Evaluate a single SX expression in the global environment. *)
+let api_eval_expr expr_js env_js =
+  let expr = js_to_value expr_js in
+  let _env = if Js.Unsafe.equals env_js Js.undefined then global_env
+             else global_env in
+  try
+    let result = Sx_ref.eval_expr expr (Env _env) in
+    return_via_side_channel (value_to_js result)
+  with Eval_error msg ->
+    Js.Unsafe.inject (Js.string ("Error: " ^ msg))
+
+(** Evaluate SX source string and return the last result. *)
+let api_eval src_js =
+  let src = Js.to_string src_js in
+  try
+    let exprs = Sx_parser.parse_all src in
+    let env = Env global_env in
+    let result = List.fold_left (fun _acc expr ->
+      Sx_ref.eval_expr expr env
+    ) Nil exprs in
+    return_via_side_channel (value_to_js result)
+  with
+  | Eval_error msg -> Js.Unsafe.inject (Js.string ("Error: " ^ msg))
+  | Parse_error msg -> Js.Unsafe.inject (Js.string ("Parse error: " ^ msg))
+
+(** Run the CEK machine on an expression, return result. *)
+let api_cek_run expr_js =
+  let expr = js_to_value expr_js in
+  try
+    let state = Sx_ref.make_cek_state expr (Env global_env) Nil in
+    let result = Sx_ref.cek_run_iterative state in
+    return_via_side_channel (value_to_js result)
+  with Eval_error msg ->
+    Js.Unsafe.inject (Js.string ("Error: " ^ msg))
+
+(** Render SX expression to HTML string. *)
+let api_render_to_html expr_js =
+  let expr = js_to_value expr_js in
+  let prev = !_sx_render_mode in
+  _sx_render_mode := true;
+  try
+    let html = Sx_render.render_to_html expr global_env in
+    _sx_render_mode := prev;
+    Js.Unsafe.inject (Js.string html)
+  with Eval_error msg ->
+    _sx_render_mode := prev;
+    Js.Unsafe.inject (Js.string ("Error: " ^ msg))
+
+(** Load SX source for side effects (define, defcomp, defmacro). *)
+let api_load src_js =
+  let src = Js.to_string src_js in
+  try
+    let exprs = Sx_parser.parse_all src in
+    let env = Env global_env in
+    let count = ref 0 in
+    List.iter (fun expr ->
+      ignore (Sx_ref.eval_expr expr env);
+      incr count
+    ) exprs;
+    Js.Unsafe.inject !count
+  with
+  | Eval_error msg -> Js.Unsafe.inject (Js.string ("Error: " ^ msg))
+  | Parse_error msg -> Js.Unsafe.inject (Js.string ("Parse error: " ^ msg))
+
+(** Get the type of an SX value. *)
+let api_type_of v_js =
+  let v = js_to_value v_js in
+  Js.Unsafe.inject (Js.string (type_of v))
+
+(** Inspect an SX value (debug string). *)
+let api_inspect v_js =
+  let v = js_to_value v_js in
+  Js.Unsafe.inject (Js.string (inspect v))
+
+(** Get engine identity. *)
+let api_engine () =
+  Js.Unsafe.inject (Js.string "ocaml-cek-wasm")
+
+(** Register a JS callback as a named native function in the global env.
+    JS callback receives JS-converted args and should return a JS value. *)
+let api_register_native name_js callback_js =
+  let name = Js.to_string name_js in
+  let native_fn args =
+    let js_args = args |> List.map value_to_js |> Array.of_list in
+    let result = Js.Unsafe.fun_call callback_js
+      [| Js.Unsafe.inject (Js.array js_args) |] in
+    js_to_value result
+  in
+  ignore (env_bind global_env name (NativeFn (name, native_fn)));
+  Js.Unsafe.inject Js.null
+
+(** Call an SX callable (lambda, native fn) with JS args.
+    fn_js can be a wrapped SX callable (with __sx_handle) or a JS value.
+    args_js is a JS array of arguments. *)
+let api_call_fn fn_js args_js =
+  try
+    let fn = js_to_value fn_js in
+    let args_arr = Js.to_array (Js.Unsafe.coerce args_js) in
+    let args = Array.to_list (Array.map js_to_value args_arr) in
+    let result = call_sx_fn fn args in
+    return_via_side_channel (value_to_js result)
+  with
+  | Eval_error msg ->
+    ignore (Js.Unsafe.meth_call (Js.Unsafe.get Js.Unsafe.global (Js.string "console"))
+      "error" [| Js.Unsafe.inject (Js.string (Printf.sprintf "[sx] callFn error: %s" msg)) |]);
+    Js.Unsafe.inject Js.null
+  | exn ->
+    ignore (Js.Unsafe.meth_call (Js.Unsafe.get Js.Unsafe.global (Js.string "console"))
+      "error" [| Js.Unsafe.inject (Js.string (Printf.sprintf "[sx] callFn error: %s" (Printexc.to_string exn))) |]);
+    Js.Unsafe.inject Js.null
+
+(** Check if a JS value is a wrapped SX callable. *)
+let api_is_callable fn_js =
+  if Js.Unsafe.equals fn_js Js.null || Js.Unsafe.equals fn_js Js.undefined then
+    Js.Unsafe.inject (Js.bool false)
+  else
+    let handle_field = Js.Unsafe.get fn_js (Js.string "__sx_handle") in
+    if not (Js.Unsafe.equals handle_field Js.undefined) then begin
+      let id = Js.float_of_number (Js.Unsafe.coerce handle_field) |> int_of_float in
+      let v = get_handle id in
+      Js.Unsafe.inject (Js.bool (is_callable v))
+    end else
+      Js.Unsafe.inject (Js.bool false)
+
+(** Get the parameter count of an SX callable (for zero-arg optimization). *)
+let api_fn_arity fn_js =
+  let handle_field = Js.Unsafe.get fn_js (Js.string "__sx_handle") in
+  if Js.Unsafe.equals handle_field Js.undefined then
+    Js.Unsafe.inject (Js.number_of_float (-1.0))
+  else
+    let id = Js.float_of_number (Js.Unsafe.coerce handle_field) |> int_of_float in
+    let v = get_handle id in
+    match v with
+    | Lambda l -> Js.Unsafe.inject (Js.number_of_float (float_of_int (List.length l.l_params)))
+    | _ -> Js.Unsafe.inject (Js.number_of_float (-1.0))
+
+(** Load and evaluate SX source string with error wrapping (for test runner). *)
+let api_load_source src_js =
+  let src = Js.to_string src_js in
+  try
+    let exprs = Sx_parser.parse_all src in
+    let env = Env global_env in
+    let count = ref 0 in
+    List.iter (fun expr ->
+      ignore (Sx_ref.eval_expr expr env);
+      incr count
+    ) exprs;
+    Js.Unsafe.inject !count
+  with
+  | Eval_error msg -> Js.Unsafe.inject (Js.string ("Error: " ^ msg))
+  | Parse_error msg -> Js.Unsafe.inject (Js.string ("Parse error: " ^ msg))
+  | exn -> Js.Unsafe.inject (Js.string ("Error: " ^ Printexc.to_string exn))
+
+(* ================================================================== *)
+(* Register global Sx object                                           *)
+(* ================================================================== *)
+
+(* ================================================================== *)
+(* Platform test functions (registered in global env)                   *)
+(* ================================================================== *)
+
+let () =
+  let bind name fn =
+    ignore (env_bind global_env name (NativeFn (name, fn)))
+  in
+
+  (* --- Deep equality --- *)
+  let rec deep_equal a b =
+    match a, b with
+    | Nil, Nil -> true
+    | Bool a, Bool b -> a = b
+    | Number a, Number b -> a = b
+    | String a, String b -> a = b
+    | Symbol a, Symbol b -> a = b
+    | Keyword a, Keyword b -> a = b
+    | (List a | ListRef { contents = a }), (List b | ListRef { contents = b }) ->
+      List.length a = List.length b && List.for_all2 deep_equal a b
+    | Dict a, Dict b ->
+      let ka = Hashtbl.fold (fun k _ acc -> k :: acc) a [] in
+      let kb = Hashtbl.fold (fun k _ acc -> k :: acc) b [] in
+      List.length ka = List.length kb &&
+      List.for_all (fun k ->
+        Hashtbl.mem b k &&
+        deep_equal
+          (match Hashtbl.find_opt a k with Some v -> v | None -> Nil)
+          (match Hashtbl.find_opt b k with Some v -> v | None -> Nil)) ka
+    | Lambda _, Lambda _ -> a == b
+    | NativeFn _, NativeFn _ -> a == b
+    | _ -> false
+  in
+
+  (* --- try-call --- *)
+  bind "try-call" (fun args ->
+    match args with
+    | [thunk] ->
+      (try
+        ignore (Sx_ref.eval_expr (List [thunk]) (Env global_env));
+        let d = Hashtbl.create 2 in
+        Hashtbl.replace d "ok" (Bool true); Dict d
+      with
+      | Eval_error msg ->
+        let d = Hashtbl.create 2 in
+        Hashtbl.replace d "ok" (Bool false);
+        Hashtbl.replace d "error" (String msg); Dict d
+      | exn ->
+        let d = Hashtbl.create 2 in
+        Hashtbl.replace d "ok" (Bool false);
+        Hashtbl.replace d "error" (String (Printexc.to_string exn)); Dict d)
+    | _ -> raise (Eval_error "try-call: expected 1 arg"));
+
+  (* --- Evaluation --- *)
+  bind "cek-eval" (fun args ->
+    match args with
+    | [expr] -> Sx_ref.eval_expr expr (Env global_env)
+    | [expr; env_val] -> Sx_ref.eval_expr expr env_val
+    | _ -> raise (Eval_error "cek-eval: expected 1-2 args"));
+
+  bind "eval-expr-cek" (fun args ->
+    match args with
+    | [expr] -> Sx_ref.eval_expr expr (Env global_env)
+    | [expr; env_val] -> Sx_ref.eval_expr expr env_val
+    | _ -> raise (Eval_error "eval-expr-cek: expected 1-2 args"));
+
+  bind "sx-parse" (fun args ->
+    match args with
+    | [String src] -> List (Sx_parser.parse_all src)
+    | _ -> raise (Eval_error "sx-parse: expected string"));
+
+  (* --- Equality and assertions --- *)
+  bind "equal?" (fun args ->
+    match args with
+    | [a; b] -> Bool (deep_equal a b)
+    | _ -> raise (Eval_error "equal?: expected 2 args"));
+
+  bind "identical?" (fun args ->
+    match args with
+    | [a; b] -> Bool (a == b)
+    | _ -> raise (Eval_error "identical?: expected 2 args"));
+
+  bind "assert" (fun args ->
+    match args with
+    | [cond] ->
+      if not (sx_truthy cond) then raise (Eval_error "Assertion failed");
+      Bool true
+    | [cond; String msg] ->
+      if not (sx_truthy cond) then raise (Eval_error ("Assertion error: " ^ msg));
+      Bool true
+    | [cond; msg] ->
+      if not (sx_truthy cond) then
+        raise (Eval_error ("Assertion error: " ^ value_to_string msg));
+      Bool true
+    | _ -> raise (Eval_error "assert: expected 1-2 args"));
+
+  (* --- List mutation --- *)
+  bind "append!" (fun args ->
+    match args with
+    | [ListRef r; v] -> r := !r @ [v]; ListRef r
+    | [List items; v] -> List (items @ [v])
+    | _ -> raise (Eval_error "append!: expected list and value"));
+
+  (* --- Environment ops --- *)
+  bind "make-env" (fun _args -> Env (make_env ()));
+
+  bind "env-has?" (fun args ->
+    match args with
+    | [Env e; String k] -> Bool (env_has e k)
+    | [Env e; Keyword k] -> Bool (env_has e k)
+    | _ -> raise (Eval_error "env-has?: expected env and key"));
+
+  bind "env-get" (fun args ->
+    match args with
+    | [Env e; String k] -> env_get e k
+    | [Env e; Keyword k] -> env_get e k
+    | _ -> raise (Eval_error "env-get: expected env and key"));
+
+  bind "env-bind!" (fun args ->
+    match args with
+    | [Env e; String k; v] -> env_bind e k v
+    | [Env e; Keyword k; v] -> env_bind e k v
+    | _ -> raise (Eval_error "env-bind!: expected env, key, value"));
+
+  bind "env-set!" (fun args ->
+    match args with
+    | [Env e; String k; v] -> env_set e k v
+    | [Env e; Keyword k; v] -> env_set e k v
+    | _ -> raise (Eval_error "env-set!: expected env, key, value"));
+
+  bind "env-extend" (fun args ->
+    match args with
+    | [Env e] -> Env (env_extend e)
+    | _ -> raise (Eval_error "env-extend: expected env"));
+
+  bind "env-merge" (fun args ->
+    match args with
+    | [Env a; Env b] -> Env (env_merge a b)
+    | _ -> raise (Eval_error "env-merge: expected 2 envs"));
+
+  (* --- Continuation support --- *)
+  bind "make-continuation" (fun args ->
+    match args with
+    | [f] ->
+      let k v = Sx_runtime.sx_call f [v] in
+      Continuation (k, None)
+    | _ -> raise (Eval_error "make-continuation: expected 1 arg"));
+
+  bind "continuation?" (fun args ->
+    match args with
+    | [Continuation _] -> Bool true
+    | [_] -> Bool false
+    | _ -> raise (Eval_error "continuation?: expected 1 arg"));
+
+  bind "continuation-fn" (fun args ->
+    match args with
+    | [Continuation (f, _)] -> NativeFn ("continuation-fn-result", fun args ->
+        (match args with [v] -> f v | _ -> f Nil))
+    | _ -> raise (Eval_error "continuation-fn: expected continuation"));
+
+  (* --- Missing primitives --- *)
+  bind "make-keyword" (fun args ->
+    match args with
+    | [String s] -> Keyword s
+    | _ -> raise (Eval_error "make-keyword: expected string"));
+
+  (* --- Test helpers --- *)
+  bind "sx-parse-one" (fun args ->
+    match args with
+    | [String src] ->
+      let exprs = Sx_parser.parse_all src in
+      (match exprs with e :: _ -> e | [] -> Nil)
+    | _ -> raise (Eval_error "sx-parse-one: expected string"));
+
+  bind "test-env" (fun _args -> Env (env_extend global_env));
+
+  (* cek-eval takes a string in the native runner *)
+  bind "cek-eval" (fun args ->
+    match args with
+    | [String s] ->
+      let exprs = Sx_parser.parse_all s in
+      (match exprs with
+       | e :: _ -> Sx_ref.eval_expr e (Env global_env)
+       | [] -> Nil)
+    | [expr] -> Sx_ref.eval_expr expr (Env global_env)
+    | [expr; env_val] -> Sx_ref.eval_expr expr env_val
+    | _ -> raise (Eval_error "cek-eval: expected 1-2 args"));
+
+  bind "eval-expr-cek" (fun args ->
+    match args with
+    | [expr; e] -> Sx_ref.eval_expr expr e
+    | [expr] -> Sx_ref.eval_expr expr (Env global_env)
+    | _ -> raise (Eval_error "eval-expr-cek: expected 1-2 args"));
+
+  (* --- Component accessors --- *)
+  bind "component-params" (fun args ->
+    match args with
+    | [Component c] -> List (List.map (fun s -> String s) c.c_params)
+    | _ -> Nil);
+
+  bind "component-body" (fun args ->
+    match args with
+    | [Component c] -> c.c_body
+    | _ -> Nil);
+
+  bind "component-has-children" (fun args ->
+    match args with
+    | [Component c] -> Bool c.c_has_children
+    | _ -> Bool false);
+
+  bind "component-affinity" (fun args ->
+    match args with
+    | [Component c] -> String c.c_affinity
+    | _ -> String "auto");
+
+  bind "component-param-types" (fun _args -> Nil);
+  bind "component-set-param-types!" (fun _args -> Nil);
+
+  (* --- Parser/symbol helpers --- *)
+  bind "keyword-name" (fun args ->
+    match args with
+    | [Keyword k] -> String k
+    | _ -> raise (Eval_error "keyword-name: expected keyword"));
+
+  bind "symbol-name" (fun args ->
+    match args with
+    | [Symbol s] -> String s
+    | _ -> raise (Eval_error "symbol-name: expected symbol"));
+
+  bind "sx-serialize" (fun args ->
+    match args with
+    | [v] -> String (inspect v)
+    | _ -> raise (Eval_error "sx-serialize: expected 1 arg"));
+
+  bind "make-symbol" (fun args ->
+    match args with
+    | [String s] -> Symbol s
+    | [v] -> Symbol (value_to_string v)
+    | _ -> raise (Eval_error "make-symbol: expected 1 arg"));
+
+  (* --- CEK stepping / introspection --- *)
+  bind "make-cek-state" (fun args ->
+    match args with
+    | [ctrl; env'; kont] -> Sx_ref.make_cek_state ctrl env' kont
+    | _ -> raise (Eval_error "make-cek-state: expected 3 args"));
+
+  bind "cek-step" (fun args ->
+    match args with
+    | [state] -> Sx_ref.cek_step state
+    | _ -> raise (Eval_error "cek-step: expected 1 arg"));
+
+  bind "cek-phase" (fun args ->
+    match args with
+    | [state] -> Sx_ref.cek_phase state
+    | _ -> raise (Eval_error "cek-phase: expected 1 arg"));
+
+  bind "cek-value" (fun args ->
+    match args with
+    | [state] -> Sx_ref.cek_value state
+    | _ -> raise (Eval_error "cek-value: expected 1 arg"));
+
+  bind "cek-terminal?" (fun args ->
+    match args with
+    | [state] -> Sx_ref.cek_terminal_p state
+    | _ -> raise (Eval_error "cek-terminal?: expected 1 arg"));
+
+  bind "cek-kont" (fun args ->
+    match args with
+    | [state] -> Sx_ref.cek_kont state
+    | _ -> raise (Eval_error "cek-kont: expected 1 arg"));
+
+  bind "frame-type" (fun args ->
+    match args with
+    | [frame] -> Sx_ref.frame_type frame
+    | _ -> raise (Eval_error "frame-type: expected 1 arg"));
+
+  (* --- Strict mode --- *)
+  ignore (env_bind global_env "*strict*" (Bool false));
+  ignore (env_bind global_env "*prim-param-types*" Nil);
+
+  bind "set-strict!" (fun args ->
+    match args with
+    | [v] ->
+      Sx_ref._strict_ref := v;
+      ignore (env_set global_env "*strict*" v); Nil
+    | _ -> raise (Eval_error "set-strict!: expected 1 arg"));
+
+  bind "set-prim-param-types!" (fun args ->
+    match args with
+    | [v] ->
+      Sx_ref._prim_param_types_ref := v;
+      ignore (env_set global_env "*prim-param-types*" v); Nil
+    | _ -> raise (Eval_error "set-prim-param-types!: expected 1 arg"));
+
+  bind "value-matches-type?" (fun args ->
+    match args with
+    | [v; String expected] -> Sx_ref.value_matches_type_p v (String expected)
+    | _ -> raise (Eval_error "value-matches-type?: expected value and type string"));
+
+  (* --- Apply --- *)
+  bind "apply" (fun args ->
+    match args with
+    | f :: rest ->
+      let all_args = match List.rev rest with
+        | List last :: prefix -> List.rev prefix @ last
+        | _ -> rest
+      in
+      Sx_runtime.sx_call f all_args
+    | _ -> raise (Eval_error "apply: expected function and args"));
+
+  (* --- Type system test helpers (for --full tests) --- *)
+  bind "test-prim-types" (fun _args ->
+    let d = Hashtbl.create 40 in
+    List.iter (fun (k, v) -> Hashtbl.replace d k (String v)) [
+      "+", "number"; "-", "number"; "*", "number"; "/", "number";
+      "mod", "number"; "inc", "number"; "dec", "number";
+      "abs", "number"; "min", "number"; "max", "number";
+      "floor", "number"; "ceil", "number"; "round", "number";
+      "str", "string"; "upper", "string"; "lower", "string";
+      "trim", "string"; "join", "string"; "replace", "string";
+      "format", "string"; "substr", "string";
+      "=", "boolean"; "<", "boolean"; ">", "boolean";
+      "<=", "boolean"; ">=", "boolean"; "!=", "boolean";
+      "not", "boolean"; "nil?", "boolean"; "empty?", "boolean";
+      "number?", "boolean"; "string?", "boolean"; "boolean?", "boolean";
+      "list?", "boolean"; "dict?", "boolean"; "symbol?", "boolean";
+      "keyword?", "boolean"; "contains?", "boolean"; "has-key?", "boolean";
+      "starts-with?", "boolean"; "ends-with?", "boolean";
+      "len", "number"; "first", "any"; "rest", "list";
+      "last", "any"; "nth", "any"; "cons", "list";
+      "append", "list"; "concat", "list"; "reverse", "list";
+      "sort", "list"; "slice", "list"; "range", "list";
+      "flatten", "list"; "keys", "list"; "vals", "list";
+      "map-dict", "dict"; "assoc", "dict"; "dissoc", "dict";
+      "merge", "dict"; "dict", "dict";
+      "get", "any"; "type-of", "string";
+    ];
+    Dict d);
+
+  bind "test-prim-param-types" (fun _args ->
+    let d = Hashtbl.create 10 in
+    let pos name typ =
+      let d2 = Hashtbl.create 2 in
+      Hashtbl.replace d2 "positional" (List [List [String name; String typ]]);
+      Hashtbl.replace d2 "rest-type" Nil; Dict d2
+    in
+    let pos_rest name typ rt =
+      let d2 = Hashtbl.create 2 in
+      Hashtbl.replace d2 "positional" (List [List [String name; String typ]]);
+      Hashtbl.replace d2 "rest-type" (String rt); Dict d2
+    in
+    Hashtbl.replace d "+" (pos_rest "a" "number" "number");
+    Hashtbl.replace d "-" (pos_rest "a" "number" "number");
+    Hashtbl.replace d "*" (pos_rest "a" "number" "number");
+    Hashtbl.replace d "/" (pos_rest "a" "number" "number");
+    Hashtbl.replace d "inc" (pos "n" "number");
+    Hashtbl.replace d "dec" (pos "n" "number");
+    Hashtbl.replace d "upper" (pos "s" "string");
+    Hashtbl.replace d "lower" (pos "s" "string");
+    Hashtbl.replace d "keys" (pos "d" "dict");
+    Hashtbl.replace d "vals" (pos "d" "dict");
+    Dict d);
+
+  (* --- HTML renderer --- *)
+  Sx_render.setup_render_env global_env;
+
+  (* Web adapters loaded as SX source at boot time via bundle.sh *)
+
+  (* Wire up render mode — the CEK machine checks these to dispatch
+     HTML tags and components to the renderer instead of eval. *)
+  Sx_runtime._render_active_p_fn :=
+    (fun () -> Bool !_sx_render_mode);
+  Sx_runtime._is_render_expr_fn :=
+    (fun expr -> match expr with
+      | List (Symbol tag :: _) ->
+        Bool (Sx_render.is_html_tag tag || tag = "<>" || tag = "raw!")
+      | _ -> Bool false);
+  Sx_runtime._render_expr_fn :=
+    (fun expr env -> match env with
+      | Env e -> RawHTML (Sx_render.render_to_html expr e)
+      | _ -> RawHTML (Sx_render.render_to_html expr global_env));
+
+  (* --- Scope stack primitives (called by transpiled evaluator via prim_call) --- *)
+  Sx_primitives.register "collect!" (fun args ->
+    match args with [a; b] -> Sx_runtime.sx_collect a b | _ -> Nil);
+  Sx_primitives.register "collected" (fun args ->
+    match args with [a] -> Sx_runtime.sx_collected a | _ -> List []);
+  Sx_primitives.register "clear-collected!" (fun args ->
+    match args with [a] -> Sx_runtime.sx_clear_collected a | _ -> Nil);
+  Sx_primitives.register "emit!" (fun args ->
+    match args with [a; b] -> Sx_runtime.sx_emit a b | _ -> Nil);
+  Sx_primitives.register "emitted" (fun args ->
+    match args with [a] -> Sx_runtime.sx_emitted a | _ -> List []);
+  Sx_primitives.register "context" (fun args ->
+    match args with [a; b] -> Sx_runtime.sx_context a b | [a] -> Sx_runtime.sx_context a Nil | _ -> Nil);
+
+  (* --- Fragment and raw HTML (always available, not just in render mode) --- *)
+  bind "<>" (fun args ->
+    let parts = List.map (fun a ->
+      match a with
+      | String s -> s
+      | RawHTML s -> s
+      | Nil -> ""
+      | List _ -> Sx_render.render_to_html a global_env
+      | _ -> value_to_string a
+    ) args in
+    RawHTML (String.concat "" parts));
+
+  bind "raw!" (fun args ->
+    match args with
+    | [String s] -> RawHTML s
+    | [RawHTML s] -> RawHTML s
+    | [Nil] -> RawHTML ""
+    | _ -> RawHTML (String.concat "" (List.map (fun a ->
+        match a with String s | RawHTML s -> s | _ -> value_to_string a
+      ) args)));
+
+  (* --- Scope stack functions (used by signals.sx, evaluator scope forms) --- *)
+  bind "scope-push!" (fun args ->
+    match args with
+    | [name; value] -> Sx_runtime.scope_push name value
+    | _ -> raise (Eval_error "scope-push!: expected 2 args"));
+
+  bind "scope-pop!" (fun args ->
+    match args with
+    | [_name] -> Sx_runtime.scope_pop _name
+    | _ -> raise (Eval_error "scope-pop!: expected 1 arg"));
+
+  bind "provide-push!" (fun args ->
+    match args with
+    | [name; value] -> Sx_runtime.provide_push name value
+    | _ -> raise (Eval_error "provide-push!: expected 2 args"));
+
+  bind "provide-pop!" (fun args ->
+    match args with
+    | [_name] -> Sx_runtime.provide_pop _name
+    | _ -> raise (Eval_error "provide-pop!: expected 1 arg"));
+
+  (* define-page-helper: registers a named page helper — stub for browser *)
+  bind "define-page-helper" (fun args ->
+    match args with
+    | [String _name; _body] -> Nil  (* Page helpers are server-side; noop in browser *)
+    | _ -> Nil);
+
+  (* cek-call: call a function via the CEK machine (used by signals, orchestration)
+     (cek-call fn nil)      → call with no args
+     (cek-call fn (list a)) → call with args list
+     (cek-call fn a)        → call with single arg *)
+  bind "cek-call" (fun args ->
+    match args with
+    | [f; Nil] -> Sx_ref.eval_expr (List [f]) (Env global_env)
+    | [f; List arg_list] -> Sx_ref.eval_expr (List (f :: arg_list)) (Env global_env)
+    | [f; a] -> Sx_ref.eval_expr (List [f; a]) (Env global_env)
+    | [f] -> Sx_ref.eval_expr (List [f]) (Env global_env)
+    | f :: rest -> Sx_ref.eval_expr (List (f :: rest)) (Env global_env)
+    | _ -> raise (Eval_error "cek-call: expected function and args"));
+
+  (* not : logical negation (sometimes missing from evaluator prims) *)
+  (if not (Sx_primitives.is_primitive "not") then
+    bind "not" (fun args ->
+      match args with
+      | [v] -> Bool (not (sx_truthy v))
+      | _ -> raise (Eval_error "not: expected 1 arg")))
+
+let () =
+  let sx = Js.Unsafe.obj [||] in
+
+  (* __sxWrap: wraps an OCaml API function so that after calling it,
+     the JS side picks up the result from globalThis.__sxR if set.
+     This bypasses js_of_ocaml stripping properties from function return values. *)
+  let wrap = Js.Unsafe.pure_js_expr
+    {|(function(fn) {
+        return function() {
+          globalThis.__sxR = undefined;
+          var r = fn.apply(null, arguments);
+          return globalThis.__sxR !== undefined ? globalThis.__sxR : r;
+        };
+      })|} in
+  let w fn = Js.Unsafe.fun_call wrap [| Js.Unsafe.inject (Js.wrap_callback fn) |] in
+
+  (* Core evaluation *)
+  Js.Unsafe.set sx (Js.string "parse")
+    (Js.wrap_callback api_parse);
+  Js.Unsafe.set sx (Js.string "stringify")
+    (Js.wrap_callback api_stringify);
+  Js.Unsafe.set sx (Js.string "eval")
+    (w api_eval);
+  Js.Unsafe.set sx (Js.string "evalExpr")
+    (w api_eval_expr);
+  Js.Unsafe.set sx (Js.string "cekRun")
+    (w api_cek_run);
+  Js.Unsafe.set sx (Js.string "renderToHtml")
+    (Js.wrap_callback api_render_to_html);
+  Js.Unsafe.set sx (Js.string "load")
+    (Js.wrap_callback api_load);
+  Js.Unsafe.set sx (Js.string "typeOf")
+    (Js.wrap_callback api_type_of);
+  Js.Unsafe.set sx (Js.string "inspect")
+    (Js.wrap_callback api_inspect);
+  Js.Unsafe.set sx (Js.string "engine")
+    (Js.wrap_callback api_engine);
+  Js.Unsafe.set sx (Js.string "registerNative")
+    (Js.wrap_callback api_register_native);
+  Js.Unsafe.set sx (Js.string "loadSource")
+    (Js.wrap_callback api_load_source);
+  Js.Unsafe.set sx (Js.string "callFn")
+    (w api_call_fn);
+  Js.Unsafe.set sx (Js.string "isCallable")
+    (Js.wrap_callback api_is_callable);
+  Js.Unsafe.set sx (Js.string "fnArity")
+    (Js.wrap_callback api_fn_arity);
+
+  (* Expose globally *)
+  Js.Unsafe.set Js.Unsafe.global (Js.string "SxKernel") sx
--- a/hosts/ocaml/dune-project
+++ b/hosts/ocaml/dune-project
@@ -1,2 +1,2 @@
-(lang dune 3.0)
+(lang dune 3.19)
 (name sx)
--- a/hosts/ocaml/lib/dune
+++ b/hosts/ocaml/lib/dune
@@ -1,2 +1,3 @@
 (library
- (name sx))
+ (name sx)
+ (wrapped false))
--- a/hosts/ocaml/lib/sx_ref.ml
+++ b/hosts/ocaml/lib/sx_ref.ml
--- a/hosts/ocaml/lib/sx_render.ml
+++ b/hosts/ocaml/lib/sx_render.ml
@@ -131,35 +131,44 @@ let render_html_element tag args env =
      (List.map (fun c -> render_to_html c env) children) in
    "<" ^ tag ^ attr_str ^ ">" ^ content ^ "</" ^ tag ^ ">"

+let render_component_generic ~params ~has_children ~body ~closure args env =
+  let kwargs = Hashtbl.create 8 in
+  let children_exprs = ref [] in
+  let skip = ref false in
+  let len = List.length args in
+  List.iteri (fun idx arg ->
+    if !skip then skip := false
+    else match arg with
+    | Keyword k when idx + 1 < len ->
+      let v = Sx_ref.eval_expr (List.nth args (idx + 1)) (Env env) in
+      Hashtbl.replace kwargs k v;
+      skip := true
+    | _ ->
+      children_exprs := arg :: !children_exprs
+  ) args;
+  let children = List.rev !children_exprs in
+  let local = env_merge closure env in
+  List.iter (fun p ->
+    let v = match Hashtbl.find_opt kwargs p with Some v -> v | None -> Nil in
+    ignore (env_bind local p v)
+  ) params;
+  if has_children then begin
+    let rendered_children = String.concat ""
+      (List.map (fun c -> render_to_html c env) children) in
+    ignore (env_bind local "children" (RawHTML rendered_children))
+  end;
+  render_to_html body local
+
 let render_component comp args env =
  match comp with
  | Component c ->
-    let kwargs = Hashtbl.create 8 in
-    let children_exprs = ref [] in
-    let skip = ref false in
-    let len = List.length args in
-    List.iteri (fun idx arg ->
-      if !skip then skip := false
-      else match arg with
-      | Keyword k when idx + 1 < len ->
-        let v = Sx_ref.eval_expr (List.nth args (idx + 1)) (Env env) in
-        Hashtbl.replace kwargs k v;
-        skip := true
-      | _ ->
-        children_exprs := arg :: !children_exprs
-    ) args;
-    let children = List.rev !children_exprs in
-    let local = env_merge c.c_closure env in
-    List.iter (fun p ->
-      let v = match Hashtbl.find_opt kwargs p with Some v -> v | None -> Nil in
-      ignore (env_bind local p v)
-    ) c.c_params;
-    if c.c_has_children then begin
-      let rendered_children = String.concat ""
-        (List.map (fun c -> render_to_html c env) children) in
-      ignore (env_bind local "children" (RawHTML rendered_children))
-    end;
-    render_to_html c.c_body local
+    render_component_generic
+      ~params:c.c_params ~has_children:c.c_has_children
+      ~body:c.c_body ~closure:c.c_closure args env
+  | Island i ->
+    render_component_generic
+      ~params:i.i_params ~has_children:i.i_has_children
+      ~body:i.i_body ~closure:i.i_closure args env
  | _ -> ""

 let expand_macro (m : macro) args _env =
@@ -249,7 +258,7 @@ and render_list_to_html head args env =
    (try
      let v = env_get env name in
      (match v with
-       | Component _ -> render_component v args env
+       | Component _ | Island _ -> render_component v args env
       | Macro m ->
         let expanded = expand_macro m args env in
         do_render_to_html expanded env
--- a/hosts/ocaml/lib/sx_runtime.ml
+++ b/hosts/ocaml/lib/sx_runtime.ml
@@ -195,13 +195,59 @@ let _is_spread_prim a = _prim "spread?" [a]
 let spread_attrs a = _prim "spread-attrs" [a]
 let make_spread a = _prim "make-spread" [a]

-(* Scope primitives — delegate to sx_ref.py's shared scope stacks *)
-let sx_collect a b = prim_call "collect!" [a; b]
-let sx_collected a = prim_call "collected" [a]
-let sx_clear_collected a = prim_call "clear-collected!" [a]
-let sx_emit a b = prim_call "emit!" [a; b]
-let sx_emitted a = prim_call "emitted" [a]
-let sx_context a b = prim_call "context" [a; b]
+(* Scope stacks — thread-local stacks keyed by name string.
+   collect!/collected implement accumulator scopes.
+   emit!/emitted implement event emission scopes.
+   context reads the top of a named scope stack. *)
+let _scope_stacks : (string, value list) Hashtbl.t = Hashtbl.create 8
+
+let sx_collect name value =
+  let key = value_to_str name in
+  let stack = match Hashtbl.find_opt _scope_stacks key with
+    | Some s -> s | None -> [] in
+  (* Push value onto the top list of the stack *)
+  (match stack with
+   | List items :: rest ->
+     Hashtbl.replace _scope_stacks key (List (items @ [value]) :: rest)
+   | _ ->
+     Hashtbl.replace _scope_stacks key (List [value] :: stack));
+  Nil
+
+let sx_collected name =
+  let key = value_to_str name in
+  match Hashtbl.find_opt _scope_stacks key with
+  | Some (List items :: _) -> List items
+  | _ -> List []
+
+let sx_clear_collected name =
+  let key = value_to_str name in
+  (match Hashtbl.find_opt _scope_stacks key with
+   | Some (_ :: rest) -> Hashtbl.replace _scope_stacks key (List [] :: rest)
+   | _ -> ());
+  Nil
+
+let sx_emit name value =
+  let key = value_to_str name in
+  let stack = match Hashtbl.find_opt _scope_stacks key with
+    | Some s -> s | None -> [] in
+  (match stack with
+   | List items :: rest ->
+     Hashtbl.replace _scope_stacks key (List (items @ [value]) :: rest)
+   | _ ->
+     Hashtbl.replace _scope_stacks key (List [value] :: stack));
+  Nil
+
+let sx_emitted name =
+  let key = value_to_str name in
+  match Hashtbl.find_opt _scope_stacks key with
+  | Some (List items :: _) -> List items
+  | _ -> List []
+
+let sx_context name default =
+  let key = value_to_str name in
+  match Hashtbl.find_opt _scope_stacks key with
+  | Some (v :: _) -> v
+  | _ -> default

 (* Trampoline — forward-declared in sx_ref.ml, delegates to CEK eval_expr *)
 (* This is a stub; the real trampoline is wired up in sx_ref.ml after eval_expr is defined *)
@@ -292,31 +338,99 @@ let dynamic_wind_call before body after _env =
  result

 (* Scope stack stubs — delegated to primitives when available *)
-let scope_push name value = prim_call "collect!" [name; value]
-let scope_pop _name = Nil
-let provide_push name value = ignore name; ignore value; Nil
-let provide_pop _name = Nil
+let scope_push name value =
+  let key = value_to_str name in
+  let stack = match Hashtbl.find_opt _scope_stacks key with
+    | Some s -> s | None -> [] in
+  Hashtbl.replace _scope_stacks key (value :: stack);
+  Nil

-(* Render mode stubs *)
-let render_active_p () = Bool false
-let render_expr _expr _env = Nil
-let is_render_expr _expr = Bool false
+let scope_pop name =
+  let key = value_to_str name in
+  (match Hashtbl.find_opt _scope_stacks key with
+   | Some (_ :: rest) -> Hashtbl.replace _scope_stacks key rest
+   | _ -> ());
+  Nil
+
+let provide_push name value = scope_push name value
+let provide_pop name = scope_pop name
+
+(* Render mode — mutable refs so browser entry point can wire up the renderer *)
+let _render_active_p_fn : (unit -> value) ref = ref (fun () -> Bool false)
+let _render_expr_fn : (value -> value -> value) ref = ref (fun _expr _env -> Nil)
+let _is_render_expr_fn : (value -> value) ref = ref (fun _expr -> Bool false)
+
+let render_active_p () = !_render_active_p_fn ()
+let render_expr expr env = !_render_expr_fn expr env
+let is_render_expr expr = !_is_render_expr_fn expr
+
+(* Signal accessors — handle both native Signal type and dict-based signals
+   from web/signals.sx which use {__signal: true, value: ..., subscribers: ..., deps: ...} *)
+let is_dict_signal d = Hashtbl.mem d "__signal"
+
+let signal_value s = match s with
+  | Signal sig' -> sig'.s_value
+  | Dict d when is_dict_signal d -> Sx_types.dict_get d "value"
+  | _ -> raise (Eval_error ("not a signal: " ^ Sx_types.type_of s))
+
+let signal_set_value s v = match s with
+  | Signal sig' -> sig'.s_value <- v; v
+  | Dict d when is_dict_signal d -> Hashtbl.replace d "value" v; v
+  | _ -> raise (Eval_error "not a signal")
+
+let signal_subscribers s = match s with
+  | Signal sig' -> List (List.map (fun _ -> Nil) sig'.s_subscribers)
+  | Dict d when is_dict_signal d -> Sx_types.dict_get d "subscribers"
+  | _ -> List []
+
+(* These use Obj.magic to accept both SX values and OCaml closures.
+   The transpiler generates bare (fun () -> ...) for reactive subscribers
+   but signal_add_sub_b expects value. This is a known transpiler limitation. *)
+let signal_add_sub_b s (f : _ ) = match s with
+  | Dict d when is_dict_signal d ->
+    let f_val : value = Obj.magic f in
+    let subs = match Sx_types.dict_get d "subscribers" with
+      | List l -> l | ListRef r -> !r | _ -> [] in
+    Hashtbl.replace d "subscribers" (List (subs @ [f_val])); Nil
+  | _ -> Nil
+
+let signal_remove_sub_b s (f : _) = match s with
+  | Dict d when is_dict_signal d ->
+    let f_val : value = Obj.magic f in
+    let subs = match Sx_types.dict_get d "subscribers" with
+      | List l -> l | ListRef r -> !r | _ -> [] in
+    Hashtbl.replace d "subscribers" (List (List.filter (fun x -> x != f_val) subs)); Nil
+  | _ -> Nil
+
+let signal_deps s = match s with
+  | Dict d when is_dict_signal d -> Sx_types.dict_get d "deps"
+  | _ -> List []
+
+let signal_set_deps s deps = match s with
+  | Dict d when is_dict_signal d -> Hashtbl.replace d "deps" deps; Nil
+  | _ -> Nil
+
+let notify_subscribers s = match s with
+  | Dict d when is_dict_signal d ->
+    let subs = match Sx_types.dict_get d "subscribers" with
+      | List l -> l | ListRef r -> !r | _ -> [] in
+    List.iter (fun sub ->
+      match sub with
+      | NativeFn (_, f) -> ignore (f [])
+      | Lambda _ -> ignore (Sx_types.env_bind (Sx_types.make_env ()) "_" Nil) (* TODO: call through CEK *)
+      | _ -> ()
+    ) subs; Nil
+  | _ -> Nil

-(* Signal accessors *)
-let signal_value s = match s with Signal sig' -> sig'.s_value | _ -> raise (Eval_error "not a signal")
-let signal_set_value s v = match s with Signal sig' -> sig'.s_value <- v; v | _ -> raise (Eval_error "not a signal")
-let signal_subscribers s = match s with Signal sig' -> List (List.map (fun _ -> Nil) sig'.s_subscribers) | _ -> List []
-let signal_add_sub_b _s _f = Nil
-let signal_remove_sub_b _s _f = Nil
-let signal_deps _s = List []
-let signal_set_deps _s _d = Nil
-let notify_subscribers _s = Nil
 let flush_subscribers _s = Nil
 let dispose_computed _s = Nil

-(* Island scope stubs — accept OCaml functions from transpiled code *)
-let with_island_scope _register_fn body_fn = body_fn ()
-let register_in_scope _dispose_fn = Nil
+(* Island scope stubs — accept OCaml functions from transpiled code.
+   Use Obj.magic for the same reason as signal_add_sub_b. *)
+let with_island_scope (_register_fn : _) (body_fn : _) =
+  let body : unit -> value = Obj.magic body_fn in
+  body ()
+let register_in_scope (_dispose_fn : _) = Nil

 (* Component type annotation stub *)
 let component_set_param_types_b _comp _types = Nil
--- a/hosts/ocaml/lib/sx_types.ml
+++ b/hosts/ocaml/lib/sx_types.ml
@@ -240,7 +240,10 @@ let is_component = function Component _ -> true | _ -> false
 let is_island = function Island _ -> true | _ -> false
 let is_macro = function Macro _ -> true | _ -> false
 let is_thunk = function Thunk _ -> true | _ -> false
-let is_signal = function Signal _ -> true | _ -> false
+let is_signal = function
+  | Signal _ -> true
+  | Dict d -> Hashtbl.mem d "__signal"
+  | _ -> false

 let is_callable = function
  | Lambda _ | NativeFn _ | Continuation (_, _) -> true
@@ -287,26 +290,32 @@ let set_lambda_name l n = match l with

 let component_name = function
  | Component c -> String c.c_name
+  | Island i -> String i.i_name
  | v -> raise (Eval_error ("Expected component, got " ^ type_of v))

 let component_params = function
  | Component c -> List (List.map (fun s -> String s) c.c_params)
+  | Island i -> List (List.map (fun s -> String s) i.i_params)
  | v -> raise (Eval_error ("Expected component, got " ^ type_of v))

 let component_body = function
  | Component c -> c.c_body
+  | Island i -> i.i_body
  | v -> raise (Eval_error ("Expected component, got " ^ type_of v))

 let component_closure = function
  | Component c -> Env c.c_closure
+  | Island i -> Env i.i_closure
  | v -> raise (Eval_error ("Expected component, got " ^ type_of v))

 let component_has_children = function
  | Component c -> Bool c.c_has_children
+  | Island i -> Bool i.i_has_children
  | v -> raise (Eval_error ("Expected component, got " ^ type_of v))

 let component_affinity = function
  | Component c -> String c.c_affinity
+  | Island _ -> String "client"
  | _ -> String "auto"

 let macro_params = function
--- a/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-041274e0.wasm
+++ b/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-041274e0.wasm
--- a/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-29ad0c09.wasm
+++ b/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-29ad0c09.wasm
--- a/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-4aee88de.wasm
+++ b/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-4aee88de.wasm
--- a/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-5f19f371.wasm
+++ b/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-5f19f371.wasm
--- a/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-7ff11249.wasm
+++ b/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-7ff11249.wasm
--- a/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-ab096041.wasm
+++ b/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-ab096041.wasm
--- a/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-d41a9499.wasm
+++ b/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-d41a9499.wasm
--- a/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-d592375f.wasm
+++ b/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-d592375f.wasm
--- a/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-ec68e6f9.wasm
+++ b/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-ec68e6f9.wasm
--- a/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-fc461d88.wasm
+++ b/shared/static/scripts/sx-wasm-assets/duneexeSx_browser-fc461d88.wasm
--- a/shared/static/scripts/sx-wasm-assets/js_of_ocaml-651f6707.wasm
+++ b/shared/static/scripts/sx-wasm-assets/js_of_ocaml-651f6707.wasm
--- a/shared/static/scripts/sx-wasm-assets/jsoo_runtime-f96b44a8.wasm
+++ b/shared/static/scripts/sx-wasm-assets/jsoo_runtime-f96b44a8.wasm
--- a/shared/static/scripts/sx-wasm-assets/prelude-d7e4b000.wasm
+++ b/shared/static/scripts/sx-wasm-assets/prelude-d7e4b000.wasm
--- a/shared/static/scripts/sx-wasm-assets/runtime-0db9b496.wasm
+++ b/shared/static/scripts/sx-wasm-assets/runtime-0db9b496.wasm
--- a/shared/static/scripts/sx-wasm-assets/start-9afa06f6.wasm
+++ b/shared/static/scripts/sx-wasm-assets/start-9afa06f6.wasm
--- a/shared/static/scripts/sx-wasm-assets/std_exit-10fb8830.wasm
+++ b/shared/static/scripts/sx-wasm-assets/std_exit-10fb8830.wasm
--- a/shared/static/scripts/sx-wasm-assets/stdlib-23ce0836.wasm
+++ b/shared/static/scripts/sx-wasm-assets/stdlib-23ce0836.wasm
--- a/shared/static/scripts/sx-wasm-assets/sx-2f171299.wasm
+++ b/shared/static/scripts/sx-wasm-assets/sx-2f171299.wasm
--- a/shared/static/scripts/sx-wasm-assets/sx-340f03ca.wasm
+++ b/shared/static/scripts/sx-wasm-assets/sx-340f03ca.wasm
--- a/shared/static/scripts/sx-wasm-assets/sx-4d3c7bfa.wasm
+++ b/shared/static/scripts/sx-wasm-assets/sx-4d3c7bfa.wasm
--- a/shared/static/scripts/sx-wasm-assets/sx-a462ed04.wasm
+++ b/shared/static/scripts/sx-wasm-assets/sx-a462ed04.wasm
--- a/shared/static/scripts/sx-wasm-assets/sx-ca2dce12.wasm
+++ b/shared/static/scripts/sx-wasm-assets/sx-ca2dce12.wasm
--- a/shared/static/scripts/sx-wasm-assets/sx-fc47a7a0.wasm
+++ b/shared/static/scripts/sx-wasm-assets/sx-fc47a7a0.wasm
--- a/shared/static/scripts/sx-wasm.js
+++ b/shared/static/scripts/sx-wasm.js
--- a/shared/sx/helpers.py
+++ b/shared/sx/helpers.py
@@ -852,6 +852,9 @@ async def sx_page(ctx: dict, page_sx: str, *,
    if body_scripts is None:
        body_scripts = _shell_cfg.get("body_scripts")

+    import os as _os
+    _sx_js_file = "sx-wasm.js" if _os.environ.get("SX_USE_WASM") == "1" else "sx-browser.js"
+
    shell_kwargs: dict[str, Any] = dict(
        title=_html_escape(title),
        asset_url=asset_url,
@@ -863,7 +866,8 @@ async def sx_page(ctx: dict, page_sx: str, *,
        page_sx=page_sx,
        sx_css=sx_css,
        sx_css_classes=sx_css_classes,
-        sx_js_hash=_script_hash("sx-browser.js"),
+        sx_js_file=_sx_js_file,
+        sx_js_hash=_script_hash(_sx_js_file),
        body_js_hash=_script_hash("body.js"),
    )
    if head_scripts is not None:
--- a/shared/sx/templates/shell.sx
+++ b/shared/sx/templates/shell.sx
@@ -16,6 +16,7 @@
                               (component-hash :as string?) (component-defs :as string?)
                               (pages-sx :as string?) (page-sx :as string?)
                               (asset-url :as string) (sx-js-hash :as string) (body-js-hash :as string?)
+                               (sx-js-file :as string?)
                               (head-scripts :as list?) (inline-css :as string?) (inline-head-js :as string?)
                               (init-sx :as string?) (body-scripts :as list?))
  (<>
@@ -74,7 +75,7 @@ details.group{overflow:hidden}details.group>summary{list-style:none}details.grou
          (raw! (or pages-sx "")))
        (script :type "text/sx" :data-mount "body"
          (raw! (or page-sx "")))
-        (script :src (str asset-url "/scripts/sx-browser.js?v=" sx-js-hash))
+        (script :src (str asset-url "/scripts/" (or sx-js-file "sx-browser.js") "?v=" sx-js-hash))
        ;; Body scripts — configurable per app
        ;; Pass a list (even empty) to override defaults; nil = use defaults
        (if (not (nil? body-scripts))