diff --git a/shared/static/scripts/sx-browser.js b/shared/static/scripts/sx-browser.js
index e92e774..9ab4a7d 100644
--- a/shared/static/scripts/sx-browser.js
+++ b/shared/static/scripts/sx-browser.js
@@ -14,7 +14,7 @@
   // =========================================================================
 
   var NIL = Object.freeze({ _nil: true, toString: function() { return "nil"; } });
-  var SX_VERSION = "2026-03-07T02:32:34Z";
+  var SX_VERSION = "2026-03-07T09:03:03Z";
 
   function isNil(x) { return x === NIL || x === null || x === undefined; }
   function isSxTruthy(x) { return x !== false && !isNil(x); }
@@ -2031,7 +2031,11 @@ return domAppendToHead(link); }, domQueryAll(container, "link[rel=\"stylesheet\"
   return (isSxTruthy(sxOr(isNil(contentSrc), isEmpty(contentSrc))) ? (logWarn((String("sx:route no content for ") + String(pathname))), false) : (function() {
   var target = resolveRouteTarget(targetSel);
   return (isSxTruthy(isNil(target)) ? (logWarn((String("sx:route target not found: ") + String(targetSel))), false) : (isSxTruthy(!isSxTruthy(depsSatisfied_p(match))) ? (logInfo((String("sx:route deps miss for ") + String(pageName))), false) : (function() {
-  var hasIo = get(match, "has-io");
+  var ioDeps = get(match, "io-deps");
+  var hasIo = (isSxTruthy(ioDeps) && !isSxTruthy(isEmpty(ioDeps)));
+  if (isSxTruthy(hasIo)) {
+  registerIoDeps(ioDeps);
+}
   return (isSxTruthy(get(match, "has-data")) ? (function() {
   var cacheKey = pageDataCacheKey(pageName, params);
   var cached = pageDataCacheGet(cacheKey);
@@ -2476,7 +2480,7 @@ callExpr.push(dictGet(kwargs, k)); } }
 })(); };
 
   // boot-init
-  var bootInit = function() { return (logInfo((String("sx-browser ") + String(SX_VERSION))), initCssTracking(), initStyleDict(), initIoPrimitives(), processPageScripts(), processSxScripts(NIL), sxHydrateElements(NIL), processElements(NIL)); };
+  var bootInit = function() { return (logInfo((String("sx-browser ") + String(SX_VERSION))), initCssTracking(), initStyleDict(), processPageScripts(), processSxScripts(NIL), sxHydrateElements(NIL), processElements(NIL)); };
 
 
   // === Transpiled from router (client-side route matching) ===
@@ -4359,16 +4363,20 @@ callExpr.push(dictGet(kwargs, k)); } }
     });
   }
 
-  // Register default proxied IO primitives
-  function initIoPrimitives() {
-    var defaults = [
-      "highlight", "current-user", "request-arg", "request-path",
-      "app-url", "asset-url", "config"
-    ];
-    for (var i = 0; i < defaults.length; i++) {
-      registerProxiedIo(defaults[i]);
+  // Register IO deps as proxied primitives (idempotent, called per-page)
+  function registerIoDeps(names) {
+    if (!names || !names.length) return;
+    var registered = 0;
+    for (var i = 0; i < names.length; i++) {
+      var name = names[i];
+      if (!IO_PRIMITIVES[name]) {
+        registerProxiedIo(name);
+        registered++;
+      }
+    }
+    if (registered > 0) {
+      logInfo("sx:io registered " + registered + " proxied primitives: " + names.join(", "));
     }
-    logInfo("sx:io registered " + defaults.length + " proxied primitives");
   }
 
 
@@ -4445,6 +4453,7 @@ callExpr.push(dictGet(kwargs, k)); } }
     matchRoute: matchRoute,
     findMatchingRoute: findMatchingRoute,
     registerIo: typeof registerIoPrimitive === "function" ? registerIoPrimitive : null,
+    registerIoDeps: typeof registerIoDeps === "function" ? registerIoDeps : null,
     asyncRender: typeof asyncSxRenderWithEnv === "function" ? asyncSxRenderWithEnv : null,
     asyncRenderToDom: typeof asyncRenderToDom === "function" ? asyncRenderToDom : null,
     _version: "ref-2.0 (boot+cssx+dom+engine+html+orchestration+parser+sx, bootstrap-compiled)"
diff --git a/shared/sx/helpers.py b/shared/sx/helpers.py
index d42b77c..c6ab201 100644
--- a/shared/sx/helpers.py
+++ b/shared/sx/helpers.py
@@ -691,14 +691,17 @@ def _build_pages_sx(service: str) -> str:
             deps = components_needed(content_src, _COMPONENT_ENV)
         deps_sx = "(" + " ".join(_sx_literal(d) for d in sorted(deps)) + ")"
 
-        # Check if any dep component has IO refs (needs async rendering)
+        # Collect IO primitive names referenced by dep components
         from .types import Component as _Comp
-        has_io = "false"
+        io_deps: set[str] = set()
         for dep_name in deps:
             comp = _COMPONENT_ENV.get(dep_name)
             if isinstance(comp, _Comp) and comp.io_refs:
-                has_io = "true"
-                break
+                io_deps.update(comp.io_refs)
+        io_deps_sx = (
+            "(" + " ".join(_sx_literal(n) for n in sorted(io_deps)) + ")"
+            if io_deps else "()"
+        )
 
         # Build closure as SX dict
         closure_parts: list[str] = []
@@ -712,7 +715,7 @@ def _build_pages_sx(service: str) -> str:
             + " :path " + _sx_literal(page_def.path)
             + " :auth " + _sx_literal(auth)
             + " :has-data " + has_data
-            + " :has-io " + has_io
+            + " :io-deps " + io_deps_sx
             + " :content " + _sx_literal(content_src)
             + " :deps " + deps_sx
             + " :closure " + closure_sx + "}"
diff --git a/shared/sx/pages.py b/shared/sx/pages.py
index a3ba7e7..46c4772 100644
--- a/shared/sx/pages.py
+++ b/shared/sx/pages.py
@@ -555,11 +555,13 @@ def mount_io_endpoint(app: Any, service_name: str) -> None:
     from .jinja_bridge import _get_request_context
     from .parser import serialize
 
-    # Allowlist of IO primitives + page helpers the client may call
-    _ALLOWED_IO = {
-        "highlight", "current-user", "request-arg", "request-path",
-        "htmx-request?", "app-url", "asset-url", "config",
-    }
+    # Build allowlist from all component IO refs across this service
+    from .jinja_bridge import _COMPONENT_ENV
+    from .types import Component as _Comp
+    _ALLOWED_IO: set[str] = set()
+    for _val in _COMPONENT_ENV.values():
+        if isinstance(_val, _Comp) and _val.io_refs:
+            _ALLOWED_IO.update(_val.io_refs)
 
     async def io_proxy(name: str) -> Any:
         if name not in _ALLOWED_IO:
@@ -607,4 +609,4 @@ def mount_io_endpoint(app: Any, service_name: str) -> None:
         view_func=io_proxy,
         methods=["GET", "POST"],
     )
-    logger.info("Mounted IO proxy endpoint for %s at /sx/io/<name>", service_name)
+    logger.info("Mounted IO proxy for %s: %s", service_name, sorted(_ALLOWED_IO))
diff --git a/shared/sx/ref/boot.sx b/shared/sx/ref/boot.sx
index 24677cc..64d91b8 100644
--- a/shared/sx/ref/boot.sx
+++ b/shared/sx/ref/boot.sx
@@ -344,7 +344,6 @@
       (log-info (str "sx-browser " SX_VERSION))
       (init-css-tracking)
       (init-style-dict)
-      (init-io-primitives)
       (process-page-scripts)
       (process-sx-scripts nil)
       (sx-hydrate-elements nil)
diff --git a/shared/sx/ref/bootstrap_js.py b/shared/sx/ref/bootstrap_js.py
index a02163b..a0ef7a1 100644
--- a/shared/sx/ref/bootstrap_js.py
+++ b/shared/sx/ref/bootstrap_js.py
@@ -385,6 +385,7 @@ class JSEmitter:
             "try-client-route": "tryClientRoute",
             "try-eval-content": "tryEvalContent",
             "try-async-eval-content": "tryAsyncEvalContent",
+            "register-io-deps": "registerIoDeps",
             "url-pathname": "urlPathname",
             "bind-inline-handler": "bindInlineHandler",
             "bind-preload": "bindPreload",
@@ -477,7 +478,6 @@ class JSEmitter:
             "process-sx-scripts": "processSxScripts",
             "process-component-script": "processComponentScript",
             "init-style-dict": "initStyleDict",
-            "init-io-primitives": "initIoPrimitives",
             "SX_VERSION": "SX_VERSION",
             "boot-init": "bootInit",
             "resolve-mount-target": "resolveMountTarget",
@@ -1733,16 +1733,20 @@ ASYNC_IO_JS = '''
     });
   }
 
-  // Register default proxied IO primitives
-  function initIoPrimitives() {
-    var defaults = [
-      "highlight", "current-user", "request-arg", "request-path",
-      "app-url", "asset-url", "config"
-    ];
-    for (var i = 0; i < defaults.length; i++) {
-      registerProxiedIo(defaults[i]);
+  // Register IO deps as proxied primitives (idempotent, called per-page)
+  function registerIoDeps(names) {
+    if (!names || !names.length) return;
+    var registered = 0;
+    for (var i = 0; i < names.length; i++) {
+      var name = names[i];
+      if (!IO_PRIMITIVES[name]) {
+        registerProxiedIo(name);
+        registered++;
+      }
+    }
+    if (registered > 0) {
+      logInfo("sx:io registered " + registered + " proxied primitives: " + names.join(", "));
     }
-    logInfo("sx:io registered " + defaults.length + " proxied primitives");
   }
 '''
 
@@ -3993,6 +3997,7 @@ def public_api_js(has_html, has_sx, has_dom, has_engine, has_orch, has_cssx, has
 
     if has_dom:
         api_lines.append('    registerIo: typeof registerIoPrimitive === "function" ? registerIoPrimitive : null,')
+        api_lines.append('    registerIoDeps: typeof registerIoDeps === "function" ? registerIoDeps : null,')
         api_lines.append('    asyncRender: typeof asyncSxRenderWithEnv === "function" ? asyncSxRenderWithEnv : null,')
         api_lines.append('    asyncRenderToDom: typeof asyncRenderToDom === "function" ? asyncRenderToDom : null,')
     api_lines.append(f'    _version: "{version}"')
diff --git a/shared/sx/ref/orchestration.sx b/shared/sx/ref/orchestration.sx
index f823648..2272a3a 100644
--- a/shared/sx/ref/orchestration.sx
+++ b/shared/sx/ref/orchestration.sx
@@ -648,7 +648,10 @@
                 (do (log-warn (str "sx:route target not found: " target-sel)) false)
                 (if (not (deps-satisfied? match))
                   (do (log-info (str "sx:route deps miss for " page-name)) false)
-                  (let ((has-io (get match "has-io")))
+                  (let ((io-deps (get match "io-deps"))
+                        (has-io (and io-deps (not (empty? io-deps)))))
+                    ;; Ensure IO deps are registered as proxied primitives
+                    (when has-io (register-io-deps io-deps))
                     (if (get match "has-data")
                       ;; Data page: check cache, else resolve asynchronously
                       (let ((cache-key (page-data-cache-key page-name params))
@@ -1024,6 +1027,8 @@
 ;;   (try-eval-content source env)  → DOM node or nil (catches eval errors)
 ;;   (try-async-eval-content source env callback) → void; async render,
 ;;     calls (callback rendered-or-nil). Used for pages with IO deps.
+;;   (register-io-deps names)       → void; ensure each IO name is registered
+;;     as a proxied IO primitive on the client. Idempotent.
 ;;   (url-pathname href)            → extract pathname from URL string
 ;;   (resolve-page-data name params cb) → void; resolves data for a named page.
 ;;     Platform decides transport (HTTP, cache, IPC, etc). Calls (cb data-dict)
diff --git a/sx/sx/async-io-demo.sx b/sx/sx/async-io-demo.sx
index f20b489..cc4fa06 100644
--- a/sx/sx/async-io-demo.sx
+++ b/sx/sx/async-io-demo.sx
@@ -41,7 +41,7 @@
       (div :class "rounded-lg border border-stone-200 bg-white p-5 space-y-3"
         (h3 :class "text-sm font-medium text-stone-500 uppercase tracking-wide" "SX async rendering spec")
         (~doc-code :code
-          (highlight ";; try-client-route dispatches on has-io flag\n(if has-io\n  ;; Async render: IO primitives proxied via /sx/io/<name>\n  (do\n    (try-async-eval-content content-src env\n      (fn (rendered)\n        (when rendered\n          (swap-rendered-content target rendered pathname))))\n    true)\n  ;; Sync render: pure components, no IO\n  (let ((rendered (try-eval-content content-src env)))\n    (swap-rendered-content target rendered pathname)))" "lisp"))))
+          (highlight ";; try-client-route reads io-deps from page registry\n(let ((io-deps (get match \"io-deps\"))\n      (has-io (and io-deps (not (empty? io-deps)))))\n  ;; Register IO deps as proxied primitives on demand\n  (when has-io (register-io-deps io-deps))\n  (if has-io\n    ;; Async render: IO primitives proxied via /sx/io/<name>\n    (do\n      (try-async-eval-content content-src env\n        (fn (rendered)\n          (when rendered\n            (swap-rendered-content target rendered pathname))))\n      true)\n    ;; Sync render: pure components, no IO\n    (let ((rendered (try-eval-content content-src env)))\n      (swap-rendered-content target rendered pathname))))" "lisp"))))
 
     ;; Architecture explanation
     (div :class "rounded-lg border border-blue-200 bg-blue-50 p-5 space-y-3"
@@ -49,8 +49,8 @@
       (ol :class "list-decimal list-inside text-blue-800 space-y-2 text-sm"
         (li "Server renders the page — " (code "highlight") " runs Python directly")
         (li "Client receives component definitions including " (code "~async-io-demo-content"))
-        (li "On client navigation, " (code "has-io") " flag routes to async renderer")
-        (li "Async renderer encounters " (code "(highlight ...)") " — checks " (code "IO_PRIMITIVES"))
+        (li "On client navigation, " (code "io-deps") " list routes to async renderer")
+        (li (code "register-io-deps") " ensures each IO name is proxied via " (code "registerProxiedIo"))
         (li "Proxied call: " (code "fetch(\"/sx/io/highlight?_arg0=...&_arg1=lisp\")"))
         (li "Server runs highlight, returns SX source (colored span elements)")
         (li "Client parses SX → AST, async renderer recursively renders to DOM")))