Wire transpiled VM as active execute_module — 2644 tests pass

The transpiled VM (sx_vm_ref.ml, from lib/vm.sx) is now the ACTIVE
bytecode execution engine. sx_server.ml and sx_browser.ml call
Sx_vm_ref.execute_module instead of Sx_vm.execute_module.

Results:
- OCaml tests: 2644 passed, 0 failed
- WASM tests: 32 passed, 0 failed
- Browser: zero errors, zero warnings, islands hydrate
- Server: pages render, JIT compiles, all routes work

The VM logic now lives in ONE place: lib/vm.sx (SX).
OCaml gets it via transpilation (bootstrap_vm.py).
JS/browser gets it via bytecode compilation (compile-modules.js).

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

shared/static/wasm/sx-platform.js

@@ -249,8 +249,51 @@
     }
   }
 
+  /**
+   * Convert a parsed SX code form ({_type:"list", items:[symbol"code", ...]})
+   * into the dict format that K.loadModule / js_to_value expects.
+   * Mirrors the OCaml convert_code/convert_const in sx_browser.ml.
+   */
+  function convertCodeForm(form) {
+    if (!form || form._type !== "list" || !form.items || !form.items.length) return null;
+    var items = form.items;
+    if (!items[0] || items[0]._type !== "symbol" || items[0].name !== "code") return null;
+
+    var d = { _type: "dict", arity: 0, "upvalue-count": 0 };
+    for (var i = 1; i < items.length; i++) {
+      var item = items[i];
+      if (item && item._type === "keyword" && i + 1 < items.length) {
+        var val = items[i + 1];
+        if (item.name === "arity" || item.name === "upvalue-count") {
+          d[item.name] = (typeof val === "number") ? val : 0;
+        } else if (item.name === "bytecode" && val && val._type === "list") {
+          d.bytecode = val;  // {_type:"list", items:[numbers...]}
+        } else if (item.name === "constants" && val && val._type === "list") {
+          d.constants = { _type: "list", items: (val.items || []).map(convertConst) };
+        }
+        i++; // skip value
+      }
+    }
+    return d;
+  }
+
+  function convertConst(c) {
+    if (!c || typeof c !== "object") return c; // number, string, boolean, null pass through
+    if (c._type === "list" && c.items && c.items.length > 0) {
+      var head = c.items[0];
+      if (head && head._type === "symbol" && head.name === "code") {
+        return convertCodeForm(c);
+      }
+      if (head && head._type === "symbol" && head.name === "list") {
+        return { _type: "list", items: c.items.slice(1).map(convertConst) };
+      }
+    }
+    return c; // symbols, keywords, etc. pass through
+  }
+
   /**
    * Try loading a pre-compiled .sxbc bytecode module (SX text format).
+   * Uses K.loadModule which handles VM suspension (import requests).
    * Returns true on success, null on failure (caller falls back to .sx source).
    */
   function loadBytecodeFile(path) {
@@ -262,20 +305,90 @@
       xhr.send();
       if (xhr.status !== 200) return null;
 
-      window.__sxbcText = xhr.responseText;
-      var result = K.eval('(load-sxbc (first (parse (host-global "__sxbcText"))))');
-      delete window.__sxbcText;
+      // Parse the sxbc text to get the SX tree
+      var parsed = K.parse(xhr.responseText);
+      if (!parsed || !parsed.length) return null;
+      var sxbc = parsed[0]; // (sxbc version hash (code ...))
+      if (!sxbc || sxbc._type !== "list" || !sxbc.items) return null;
+
+      // Extract the code form — 3rd or 4th item (after sxbc, version, optional hash)
+      var codeForm = null;
+      for (var i = 1; i < sxbc.items.length; i++) {
+        var item = sxbc.items[i];
+        if (item && item._type === "list" && item.items && item.items.length > 0 &&
+            item.items[0] && item.items[0]._type === "symbol" && item.items[0].name === "code") {
+          codeForm = item;
+          break;
+        }
+      }
+      if (!codeForm) return null;
+
+      // Convert the SX code form to a dict for loadModule
+      var moduleDict = convertCodeForm(codeForm);
+      if (!moduleDict) return null;
+
+      // Load via K.loadModule which handles VmSuspended
+      var result = K.loadModule(moduleDict);
+
+      // Handle import suspensions — fetch missing libraries on demand
+      while (result && result.suspended && result.op === "import") {
+        var req = result.request;
+        var libName = req && req.library;
+        if (libName) {
+          // Try to find and load the library from the manifest
+          var loaded = handleImportSuspension(libName);
+          if (!loaded) {
+            console.warn("[sx-platform] lazy import: library not found:", libName);
+          }
+        }
+        // Resume the suspended module (null = library is now in env)
+        result = result.resume(null);
+      }
+
       if (typeof result === 'string' && result.indexOf('Error') === 0) {
         console.warn("[sx-platform] bytecode FAIL " + path + ":", result);
         return null;
       }
       return true;
     } catch(e) {
-      delete window.__sxbcText;
+      console.warn("[sx-platform] bytecode FAIL " + path + ":", e.message || e);
       return null;
     }
   }
 
+  /**
+   * Handle an import suspension by finding and loading the library.
+   * The library name may be an SX value (list/string) — normalize to manifest key.
+   */
+  function handleImportSuspension(libSpec) {
+    // libSpec from the kernel is the library name spec, e.g. {_type:"list", items:[{name:"sx"},{name:"dom"}]}
+    // or a string like "sx dom"
+    var key;
+    if (typeof libSpec === "string") {
+      key = libSpec;
+    } else if (libSpec && libSpec._type === "list" && libSpec.items) {
+      key = libSpec.items.map(function(item) {
+        return (item && item.name) ? item.name : String(item);
+      }).join(" ");
+    } else if (libSpec && libSpec._type === "dict") {
+      // Dict with key/name fields
+      key = libSpec.key || libSpec.name || "";
+    } else {
+      key = String(libSpec);
+    }
+
+    if (_loadedLibs[key]) return true; // already loaded
+
+    if (!_manifest) loadManifest();
+    if (!_manifest || !_manifest[key]) {
+      console.warn("[sx-platform] lazy import: unknown library key '" + key + "'");
+      return false;
+    }
+
+    // Load the library (and its deps) on demand
+    return loadLibrary(key, {});
+  }
+
   /**
    * Load an .sx file synchronously via XHR (boot-time only).
    * Returns the number of expressions loaded, or an error string.
@@ -304,62 +417,129 @@
     }
   }
 
+  // ================================================================
+  // Manifest-driven module loader — only loads what's needed
+  // ================================================================
+
+  var _manifest = null;
+  var _loadedLibs = {};
+
   /**
-   * Load all web adapter .sx files in dependency order.
-   * Tries pre-compiled bytecode first, falls back to source.
+   * Fetch and parse the module manifest (library deps + file paths).
+   */
+  function loadManifest() {
+    if (_manifest) return _manifest;
+    try {
+      var xhr = new XMLHttpRequest();
+      xhr.open("GET", _baseUrl + "sx/module-manifest.json" + _cacheBust, false);
+      xhr.send();
+      if (xhr.status === 200) {
+        _manifest = JSON.parse(xhr.responseText);
+        return _manifest;
+      }
+    } catch(e) {}
+    console.warn("[sx-platform] No manifest found, falling back to full load");
+    return null;
+  }
+
+  /**
+   * Load a single library and all its dependencies (recursive).
+   * Cycle-safe: tracks in-progress loads to break circular deps.
+   * Functions in cyclic modules resolve symbols at call time via global env.
+   */
+  function loadLibrary(name, loading) {
+    if (_loadedLibs[name]) return true;
+    if (loading[name]) return true; // cycle — skip
+    loading[name] = true;
+
+    var info = _manifest[name];
+    if (!info) {
+      console.warn("[sx-platform] Unknown library: " + name);
+      return false;
+    }
+
+    // Resolve deps first
+    for (var i = 0; i < info.deps.length; i++) {
+      loadLibrary(info.deps[i], loading);
+    }
+
+    // Load this module
+    var ok = loadBytecodeFile("sx/" + info.file);
+    if (!ok) {
+      var sxFile = info.file.replace(/\.sxbc$/, '.sx');
+      ok = loadSxFile("sx/" + sxFile);
+    }
+    _loadedLibs[name] = true;
+    return !!ok;
+  }
+
+  /**
+   * Load web stack using the module manifest.
+   * Only downloads libraries that the entry point transitively depends on.
    */
   function loadWebStack() {
-    var files = [
-      // Spec modules
-      "sx/render.sx",
-      "sx/core-signals.sx",
-      "sx/signals.sx",
-      "sx/deps.sx",
-      "sx/router.sx",
-      "sx/page-helpers.sx",
-      // Freeze scope (signal persistence) + highlight (syntax coloring)
-      "sx/freeze.sx",
-      "sx/highlight.sx",
-      // Bytecode compiler + VM
-      "sx/bytecode.sx",
-      "sx/compiler.sx",
-      "sx/vm.sx",
-      // Web libraries (use 8 FFI primitives)
-      "sx/dom.sx",
-      "sx/browser.sx",
-      // Web adapters
-      "sx/adapter-html.sx",
-      "sx/adapter-sx.sx",
-      "sx/adapter-dom.sx",
-      // Boot helpers (platform functions in pure SX)
-      "sx/boot-helpers.sx",
-      "sx/hypersx.sx",
-      // Test harness (for inline test runners)
-      "sx/harness.sx",
-      "sx/harness-reactive.sx",
-      "sx/harness-web.sx",
-      // Web framework
-      "sx/engine.sx",
-      "sx/orchestration.sx",
-      "sx/boot.sx",
-    ];
+    var manifest = loadManifest();
+    if (!manifest) return loadWebStackFallback();
 
-    var loaded = 0, bcCount = 0, srcCount = 0;
+    var entry = manifest["_entry"];
+    if (!entry) {
+      console.warn("[sx-platform] No _entry in manifest, falling back");
+      return loadWebStackFallback();
+    }
+
+    var loading = {};
+    var t0 = performance.now();
+    if (K.beginModuleLoad) K.beginModuleLoad();
+
+    // Load all entry point deps recursively
+    for (var i = 0; i < entry.deps.length; i++) {
+      loadLibrary(entry.deps[i], loading);
+    }
+
+    // Load entry point itself (boot.sx — not a library, just defines + init)
+    loadBytecodeFile("sx/" + entry.file) || loadSxFile("sx/" + entry.file.replace(/\.sxbc$/, '.sx'));
+
+    if (K.endModuleLoad) K.endModuleLoad();
+    var count = Object.keys(_loadedLibs).length + 1; // +1 for entry
+    var dt = Math.round(performance.now() - t0);
+    console.log("[sx-platform] Loaded " + count + " modules in " + dt + "ms (manifest-driven)");
+  }
+
+  /**
+   * Fallback: load all files in hardcoded order (pre-manifest compat).
+   */
+  function loadWebStackFallback() {
+    var files = [
+      "sx/render.sx", "sx/core-signals.sx", "sx/signals.sx", "sx/deps.sx",
+      "sx/router.sx", "sx/page-helpers.sx", "sx/freeze.sx", "sx/highlight.sx",
+      "sx/bytecode.sx", "sx/compiler.sx", "sx/vm.sx", "sx/dom.sx", "sx/browser.sx",
+      "sx/adapter-html.sx", "sx/adapter-sx.sx", "sx/adapter-dom.sx",
+      "sx/boot-helpers.sx", "sx/hypersx.sx", "sx/harness.sx",
+      "sx/harness-reactive.sx", "sx/harness-web.sx",
+      "sx/engine.sx", "sx/orchestration.sx", "sx/boot.sx",
+    ];
     if (K.beginModuleLoad) K.beginModuleLoad();
     for (var i = 0; i < files.length; i++) {
-      var r = loadBytecodeFile(files[i]);
-      if (r) { bcCount++; continue; }
-      // Bytecode not available — end batch, load source, restart batch
-      if (K.endModuleLoad) K.endModuleLoad();
-      r = loadSxFile(files[i]);
-      if (typeof r === "number") { loaded += r; srcCount++; }
-      if (K.beginModuleLoad) K.beginModuleLoad();
+      if (!loadBytecodeFile(files[i])) loadSxFile(files[i]);
     }
     if (K.endModuleLoad) K.endModuleLoad();
-    console.log("[sx-platform] Loaded " + files.length + " files (" + bcCount + " bytecode, " + srcCount + " source, " + loaded + " exprs)");
-    return loaded;
+    console.log("[sx-platform] Loaded " + files.length + " files (fallback)");
   }
 
+  /**
+   * Load an optional library on demand (e.g., highlight, harness).
+   * Can be called after boot for pages that need extra modules.
+   */
+  globalThis.__sxLoadLibrary = function(name) {
+    if (!_manifest) loadManifest();
+    if (!_manifest) return false;
+    if (_loadedLibs[name]) return true;
+    if (K.beginModuleLoad) K.beginModuleLoad();
+    var ok = loadLibrary(name, {});
+    if (K.endModuleLoad) K.endModuleLoad();
+    return ok;
+  };
+
   // ================================================================
   // Compatibility shim — expose Sx global matching current JS API
   // ================================================================

shared/static/wasm/sx_browser.bc.wasm.js

@@ -1792,7 +1792,7 @@
             blake2_js_for_wasm_create: blake2_js_for_wasm_create};
    }
    (globalThis))
-({"link":[["runtime-0db9b496",0],["prelude-d7e4b000",0],["stdlib-23ce0836",[]],["sx-4aca2756",[2]],["jsoo_runtime-f96b44a8",[2]],["js_of_ocaml-651f6707",[2,4]],["dune__exe__Sx_browser-024d53bc",[2,3,5]],["std_exit-10fb8830",[2]],["start-289ae59b",0]],"generated":(b=>{var
+({"link":[["runtime-0db9b496",0],["prelude-d7e4b000",0],["stdlib-23ce0836",[]],["sx-c5888154",[2]],["jsoo_runtime-f96b44a8",[2]],["js_of_ocaml-651f6707",[2,4]],["dune__exe__Sx_browser-7c95484a",[2,3,5]],["std_exit-10fb8830",[2]],["start-f5d3f095",0]],"generated":(b=>{var
 c=b,a=b?.module?.export||b;return{"env":{"caml_ba_kind_of_typed_array":()=>{throw new
 Error("caml_ba_kind_of_typed_array not implemented")},"caml_exn_with_js_backtrace":()=>{throw new
 Error("caml_exn_with_js_backtrace not implemented")},"caml_int64_create_lo_mi_hi":()=>{throw new