diff --git a/hosts/ocaml/lib/sx_primitives.ml b/hosts/ocaml/lib/sx_primitives.ml
index c1c17cb6..1dc86f91 100644
--- a/hosts/ocaml/lib/sx_primitives.ml
+++ b/hosts/ocaml/lib/sx_primitives.ml
@@ -667,6 +667,25 @@ let () =
     | _ -> raise (Eval_error "error: 1 arg"));
   (* client? — false by default (server); sx_browser.ml sets _is_client := true *)
   register "client?" (fun _args -> Bool !_is_client);
+  (* Named stores — global mutable registry, bypasses env scoping issues *)
+  let store_registry : (string, value) Hashtbl.t = Hashtbl.create 16 in
+  register "def-store" (fun args ->
+    match args with
+    | [String name; init_fn] ->
+      if not (Hashtbl.mem store_registry name) then begin
+        let store = !_sx_trampoline_fn (!_sx_call_fn init_fn []) in
+        Hashtbl.replace store_registry name store
+      end;
+      (match Hashtbl.find_opt store_registry name with Some v -> v | None -> Nil)
+    | _ -> raise (Eval_error "def-store: expected (name init-fn)"));
+  register "use-store" (fun args ->
+    match args with
+    | [String name] ->
+      (match Hashtbl.find_opt store_registry name with
+       | Some v -> v
+       | None -> raise (Eval_error ("Store not found: " ^ name)))
+    | _ -> raise (Eval_error "use-store: expected (name)"));
+  register "clear-stores" (fun _args -> Hashtbl.clear store_registry; Nil);
   register "apply" (fun args ->
     let call f a =
       match f with
diff --git a/shared/static/wasm/sx-platform.js b/shared/static/wasm/sx-platform.js
index 6a1cdc0b..5e64c5d9 100644
--- a/shared/static/wasm/sx-platform.js
+++ b/shared/static/wasm/sx-platform.js
@@ -199,7 +199,6 @@
 
   /**
    * Deserialize type-tagged JSON constant back to JS value for loadModule.
-   * (Legacy — used for .sxbc.json fallback)
    */
   function deserializeConstant(c) {
     if (!c || !c.t) return null;
@@ -229,61 +228,35 @@
   }
 
   /**
-   * Try loading a pre-compiled bytecode module.
-   * Tries .sxbc (s-expression) first, falls back to .sxbc.json (legacy).
+   * Try loading a pre-compiled .sxbc.json bytecode module.
    * Returns true on success, null on failure (caller falls back to .sx source).
    */
   function loadBytecodeFile(path) {
-    // Try .sxbc (s-expression format) first
-    var sxbcPath = path.replace(/\.sx$/, '.sxbc');
-    var url = _baseUrl + sxbcPath + _cacheBust;
+    var bcPath = path.replace(/\.sx$/, '.sxbc.json');
+    var url = _baseUrl + bcPath + _cacheBust;
     try {
       var xhr = new XMLHttpRequest();
       xhr.open("GET", url, false);
       xhr.send();
-      if (xhr.status === 200 && xhr.responseText.indexOf("(sxbc") === 0) {
-        // Parse with the SX kernel — returns the (sxbc ...) form
-        var parsed = K.eval('(first (sx-parse ' + JSON.stringify(xhr.responseText) + '))');
-        // (sxbc version hash (code ...)) — third element is the module
-        var module = K.eval('(nth (sx-parse ' + JSON.stringify(xhr.responseText) + ') 0)');
-        // Use evalSxbc which understands the sxbc format
-        var result = K.eval('(load-sxbc (first (sx-parse ' + JSON.stringify(xhr.responseText) + ')))');
-        if (typeof result === 'string' && result.indexOf('Error') === 0) {
-          console.warn("[sx-platform] sxbc FAIL " + path + ":", result);
-        } else {
-          return true;
-        }
-      }
-    } catch(e) {
-      // Fall through to JSON
-    }
+      if (xhr.status !== 200) return null;
 
-    // Fallback: .sxbc.json (legacy format)
-    var bcPath = path.replace(/\.sx$/, '.sxbc.json');
-    url = _baseUrl + bcPath + _cacheBust;
-    try {
-      var xhr2 = new XMLHttpRequest();
-      xhr2.open("GET", url, false);
-      xhr2.send();
-      if (xhr2.status !== 200) return null;
-
-      var json = JSON.parse(xhr2.responseText);
+      var json = JSON.parse(xhr.responseText);
       if (!json.module || json.magic !== 'SXBC') return null;
 
-      var module2 = {
+      var module = {
         _type: 'dict',
         bytecode: { _type: 'list', items: json.module.bytecode },
         constants: { _type: 'list', items: json.module.constants.map(deserializeConstant) },
       };
 
-      var result2 = K.loadModule(module2);
-      if (typeof result2 === 'string' && result2.indexOf('Error') === 0) {
-        console.warn("[sx-platform] bytecode FAIL " + path + ":", result2);
+      var result = K.loadModule(module);
+      if (typeof result === 'string' && result.indexOf('Error') === 0) {
+        console.warn("[sx-platform] bytecode FAIL " + path + ":", result);
         return null;
       }
+      console.log("[sx-platform]  ok " + path + " (bytecode)");
       return true;
     } catch(e) {
-      console.error("[sx-platform] bytecode EXCEPTION " + path + ":", e);
       return null;
     }
   }
@@ -356,23 +329,18 @@
     ];
 
     var loaded = 0, bcCount = 0, srcCount = 0;
-    var t0 = performance.now();
-    var forceSrc = (typeof window !== "undefined" && window.location.search.indexOf("nosxbc") !== -1);
-    if (!forceSrc && K.beginModuleLoad) K.beginModuleLoad();
+    if (K.beginModuleLoad) K.beginModuleLoad();
     for (var i = 0; i < files.length; i++) {
-      if (!forceSrc) {
-        var r = loadBytecodeFile(files[i]);
-        if (r) { bcCount++; continue; }
-      }
+      var r = loadBytecodeFile(files[i]);
+      if (r) { bcCount++; continue; }
       // Bytecode not available — end batch, load source, restart batch
-      if (!forceSrc && K.endModuleLoad) K.endModuleLoad();
+      if (K.endModuleLoad) K.endModuleLoad();
       r = loadSxFile(files[i]);
       if (typeof r === "number") { loaded += r; srcCount++; }
-      if (!forceSrc && K.beginModuleLoad) K.beginModuleLoad();
+      if (K.beginModuleLoad) K.beginModuleLoad();
     }
-    if (!forceSrc && K.endModuleLoad) K.endModuleLoad();
-    var elapsed = Math.round(performance.now() - t0);
-    console.log("[sx-platform] Loaded " + files.length + " files (" + bcCount + " bytecode, " + srcCount + " source, " + loaded + " exprs) in " + elapsed + "ms");
+    if (K.endModuleLoad) K.endModuleLoad();
+    console.log("[sx-platform] Loaded " + files.length + " files (" + bcCount + " bytecode, " + srcCount + " source, " + loaded + " exprs)");
     return loaded;
   }
 
@@ -390,33 +358,46 @@
     engine: function() { return K.engine(); },
     // Boot entry point (called by auto-init or manually)
     init: function() {
-      if (typeof K.eval !== "function") return;
-      var steps = [
-        '(log-info (str "sx-browser " SX_VERSION))',
-        '(init-css-tracking)',
-        '(process-page-scripts)',
-        '(process-sx-scripts nil)',
-        '(sx-hydrate-elements nil)',
-        '(sx-hydrate-islands nil)',
-        '(run-post-render-hooks)',
-        '(process-elements nil)',
-        '(dom-listen (dom-window) "popstate" (fn (e) (handle-popstate 0)))'
-      ];
-      var failures = [];
-      for (var i = 0; i < steps.length; i++) {
-        try {
-          var r = K.eval(steps[i]);
-          if (typeof r === "string" && r.indexOf("Error") === 0) {
-            console.error("[sx] boot step " + i + " FAILED: " + steps[i].substring(0, 60), r);
-            failures.push({ step: i, expr: steps[i], error: r });
-          }
-        } catch(e) {
-          console.error("[sx] boot step " + i + " THREW: " + steps[i].substring(0, 60), e);
-          failures.push({ step: i, expr: steps[i], error: String(e) });
+      if (typeof K.eval === "function") {
+        // Check boot-init exists
+        // Step through boot manually
+        console.log("[sx] init-css-tracking...");
+        K.eval("(init-css-tracking)");
+        console.log("[sx] process-page-scripts...");
+        K.eval("(process-page-scripts)");
+        console.log("[sx] routes after pages:", K.eval("(len _page-routes)"));
+        console.log("[sx] process-sx-scripts...");
+        K.eval("(process-sx-scripts nil)");
+        console.log("[sx] sx-hydrate-elements...");
+        K.eval("(sx-hydrate-elements nil)");
+        console.log("[sx] sx-hydrate-islands...");
+        K.eval("(sx-hydrate-islands nil)");
+        console.log("[sx] process-elements...");
+        K.eval("(process-elements nil)");
+        // Debug islands
+        console.log("[sx] ~home/stepper defined?", K.eval("(type-of ~home/stepper)"));
+        console.log("[sx] ~layouts/header defined?", K.eval("(type-of ~layouts/header)"));
+        // Island count (JS-side, avoids VM overhead)
+        console.log("[sx] manual island query:", document.querySelectorAll("[data-sx-island]").length);
+        // Try hydrating again
+        console.log("[sx] retry hydrate-islands...");
+        K.eval("(sx-hydrate-islands nil)");
+        // Check if links are boosted
+        var links = document.querySelectorAll("a[href]");
+        var boosted = 0;
+        for (var i = 0; i < links.length; i++) {
+          if (links[i]._sxBoundboost) boosted++;
         }
-      }
-      if (failures.length > 0) {
-        console.error("[sx] BOOT FAILED: " + failures.length + " step(s) errored:", failures.map(function(f) { return "step " + f.step + ": " + f.error; }).join("; "));
+        console.log("[sx] boosted links:", boosted, "/", links.length);
+        // Check island state
+        var islands = document.querySelectorAll("[data-sx-island]");
+        console.log("[sx] islands:", islands.length);
+        for (var j = 0; j < islands.length; j++) {
+          console.log("[sx]   island:", islands[j].getAttribute("data-sx-island"),
+            "hydrated:", !!islands[j]._sxBoundislandhydrated || !!islands[j]["_sxBound" + "island-hydrated"],
+            "children:", islands[j].children.length);
+        }
+        console.log("[sx] boot done");
       }
     }
   };
@@ -429,8 +410,8 @@
     var _doInit = function() {
       loadWebStack();
       Sx.init();
-      // JIT disabled for debugging
-      // setTimeout(function() { K.eval('(enable-jit!)'); }, 0);
+      // Enable JIT after all boot code has run
+      setTimeout(function() { K.eval('(enable-jit!)'); }, 0);
     };
 
     if (document.readyState === "loading") {
diff --git a/shared/static/wasm/sx_browser.bc.wasm.assets/sx-6f7dfa09.wasm b/shared/static/wasm/sx_browser.bc.wasm.assets/sx-6f7dfa09.wasm
new file mode 100644
index 00000000..4fa5c0c1
Binary files /dev/null and b/shared/static/wasm/sx_browser.bc.wasm.assets/sx-6f7dfa09.wasm differ
diff --git a/shared/static/wasm/sx_browser.bc.wasm.js b/shared/static/wasm/sx_browser.bc.wasm.js
index d18ee436..4efdab08 100644
--- a/shared/static/wasm/sx_browser.bc.wasm.js
+++ b/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-951e6734",[2]],["jsoo_runtime-f96b44a8",[2]],["js_of_ocaml-651f6707",[2,4]],["dune__exe__Sx_browser-6b156118",[2,3,5]],["std_exit-10fb8830",[2]],["start-80fdb768",0]],"generated":(b=>{var
+({"link":[["runtime-0db9b496",0],["prelude-d7e4b000",0],["stdlib-23ce0836",[]],["sx-6f7dfa09",[2]],["jsoo_runtime-f96b44a8",[2]],["js_of_ocaml-651f6707",[2,4]],["dune__exe__Sx_browser-6b156118",[2,3,5]],["std_exit-10fb8830",[2]],["start-80fdb768",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
diff --git a/tests/playwright/isomorphic.spec.js b/tests/playwright/isomorphic.spec.js
index 45d5a101..bcffe216 100644
--- a/tests/playwright/isomorphic.spec.js
+++ b/tests/playwright/isomorphic.spec.js
@@ -177,7 +177,9 @@ test.describe('Isomorphic SSR', () => {
   });
 
   test.fixme('navigation preserves header island state', async ({ page }) => {
-    // BUG: def-store state not persisting — *store-registry* likely reset during SPA nav component reload
+    // BUG: client? primitive works from K.eval but not during render-to-dom hydration.
+    // Needs JIT/env investigation — the pre-existing JIT "Not callable: nil" bug
+    // prevents primitives registered after boot from being called during component eval.
     await page.goto(BASE_URL + '/sx/', { waitUntil: 'networkidle' });
 
     // Wait for header island to hydrate
diff --git a/web/web-signals.sx b/web/web-signals.sx
index 14d4280b..93eadb7c 100644
--- a/web/web-signals.sx
+++ b/web/web-signals.sx
@@ -35,25 +35,9 @@
 ;; Named stores — page-level signal containers
 ;; --------------------------------------------------------------------------
 
-(define *store-registry* (dict))
-
-(define def-store :effects [mutation]
-  (fn ((name :as string) (init-fn :as lambda))
-    (let ((registry *store-registry*))
-      (when (not (has-key? registry name))
-        (set! *store-registry* (assoc registry name (cek-call init-fn nil))))
-      (get *store-registry* name))))
-
-(define use-store :effects []
-  (fn ((name :as string))
-    (if (has-key? *store-registry* name)
-      (get *store-registry* name)
-      (error (str "Store not found: " name
-                  ". Call (def-store ...) before (use-store ...).")))))
-
-(define clear-stores :effects [mutation]
-  (fn ()
-    (set! *store-registry* (dict))))
+;; def-store, use-store, clear-stores are now OCaml primitives
+;; (sx_primitives.ml) with a global mutable registry that survives
+;; env scoping across bytecode modules and island hydration.
 
 
 ;; --------------------------------------------------------------------------