diff --git a/docs/features/async/17-mailbox-scheduler-plan.md b/docs/features/async/17-mailbox-scheduler-plan.md
index cee0cc0..f1c49a8 100644
--- a/docs/features/async/17-mailbox-scheduler-plan.md
+++ b/docs/features/async/17-mailbox-scheduler-plan.md
@@ -235,6 +235,24 @@ rollback = the `WX_SCHEDULER=0` build + a per-step tag.
   3. modal dialog (`startModal` + `_wxModalResolvers` die),
   4. clipboard + font enum,
   5. **open** last — the biggest semantic flip (gates → ordering; N2/N3/N6 are the gate).
+  > **Work log 2026-08-05 — S4 LANDED and gated (waits 1–3; 4–5 resolved by scoping).**
+  > The doc-13 §2 API exists as `wx/wasm/private/yieldwait.h` (`wxWasmBeginWait` /
+  > `wxWasmYieldUntil` / `wxWasmResolveWait`/`ResolveTopWait`) backed by the shim's wait
+  > registry (per-kind LIFO stacks, resolve-before-yield safe). On scheduler builds:
+  > **nested loops, popups, and modals are registered WAITS with NO pumps** — the top-level
+  > tick is the sole dispatcher at any DoRun depth (the s_wxRunDepth gate is scheduler-
+  > bypassed; the June §6e double-driver hazard needed two awaited pumps, which no longer
+  > exist). Dead on scheduler builds: `startModal`, `wxWasmRunNestedLoop`, the wx-dom popup
+  > pump, `_wxModalResolvers`, `_wxNestedLoopExit`, `_pendingModalResult` (waits begin
+  > before Show(), so a racing EndModal pre-resolves). Tick error containment now releases
+  > the innermost nested wait AND cancels the top modal (the dead pumps' catch role).
+  > Waits 4–5 by scoping: clipboard/font enum keep their EM_ASYNC_JS promise-waits — they
+  > have no pumps and are already S2-managed sleeps (migrating them to tokens buys
+  > uniformity, not behavior; revisit at S5 if the token registry should own ALL waits);
+  > open keeps the C++ gate as second line under the JS embind lane's queueing (N2-gated
+  > since S1). **Gates:** asyncify 9/9 (triple-modal LIFO now on wait stacks), coroutine
+  > 39/39 (quasi-modal with zero pumps), wx modal-heavy 45/45, kicad 6/6 incl.
+  > modal-stack + contextmenu-scrollbar on a fresh warm-cache build.
 - **S5 · Guard demolition (few d).** Delete: dispatch interlock + save/zero/restore sites,
   timer retry, `ProcessEvents` Paint-only gate, `s_wxRunDepth` gate, open-settle/fiber-busy/
   enumerate gates. Downgrade libcontext refusals to dev-build assertions; keep counters-only
diff --git a/scripts/common/shims/asyncify-scheduler.js b/scripts/common/shims/asyncify-scheduler.js
index f71bdc0..eb71d06 100644
--- a/scripts/common/shims/asyncify-scheduler.js
+++ b/scripts/common/shims/asyncify-scheduler.js
@@ -148,6 +148,64 @@ if (typeof Asyncify !== "undefined" && !globalThis.__wxSchedulerInstalled) {
       }, 16);
     },
 
+    // --- S4 wait registry ---------------------------------------------------
+    // Token-based waits (doc 13 §2: wasm_begin_async_wait / wasm_yield_until /
+    // wasm_resolve_wait). A wait is begun BEFORE the C++ side parks, so a
+    // resolve that races ahead of the park (EndModal during Show()) simply
+    // pre-resolves the promise — yieldUntil then returns immediately. Per-kind
+    // LIFO stacks give wx modal/nested semantics ("innermost first") without
+    // the legacy per-wait resolver stacks (_wxModalResolvers /
+    // _wxNestedLoopExit), which die on scheduler builds. Resolution flows
+    // through the S2 deferred-wake law automatically: resolving a wait wakes
+    // its parked sleep via the wrapped handleSleep path.
+    waits: new Map(),      // token → {kind, promise, resolve, resolved}
+    waitSeq: 0,
+    waitStacks: {},        // kind → [unresolved tokens], LIFO
+    waitsBegun: 0,
+    waitsResolved: 0,
+    beginWait: function (kind) {
+      var token = ++this.waitSeq;
+      var entry = { kind: kind, resolved: false, resolve: null, promise: null };
+      var self = this;
+      entry.promise = new Promise(function (resolve) { entry.resolve = resolve; });
+      this.waits.set(token, entry);
+      (this.waitStacks[kind] = this.waitStacks[kind] || []).push(token);
+      this.waitsBegun++;
+      return token;
+    },
+    waitPromise: function (token) {
+      var entry = this.waits.get(token);
+      if (!entry) {
+        console.warn("[wx-scheduler] waitPromise(" + token + "): unknown token");
+        return Promise.resolve(0);
+      }
+      return entry.promise;
+    },
+    resolveWait: function (token, result) {
+      var entry = this.waits.get(token);
+      if (!entry || entry.resolved) return false;
+      entry.resolved = true;
+      this.waitsResolved++;
+      var stack = this.waitStacks[entry.kind];
+      if (stack) {
+        var idx = stack.indexOf(token);
+        if (idx !== -1) stack.splice(idx, 1);
+      }
+      this.waits.delete(token);
+      entry.resolve(result | 0);
+      return true;
+    },
+    // Resolve the INNERMOST unresolved wait of a kind (wx LIFO semantics).
+    resolveTopWait: function (kind, result) {
+      var stack = this.waitStacks[kind];
+      if (!stack || stack.length === 0) return false;
+      return this.resolveWait(stack[stack.length - 1], result);
+    },
+    pendingWaits: function (kind) {
+      var stack = this.waitStacks[kind];
+      return stack ? stack.length : 0;
+    },
+
     // --- S2 scheduler core state -------------------------------------------
     // Deferred sleep wakes: {deliver, result} queued because a transition was
     // in flight when the wake arrived. Delivered FIFO from a clean macrotask.
@@ -175,7 +233,10 @@ if (typeof Asyncify !== "undefined" && !globalThis.__wxSchedulerInstalled) {
         + " readyWakes=" + this.readyWakes.length
         + " deferredWakes=" + this.deferredWakes
         + " drainedWakes=" + this.drainedWakes
-        + " strayWrites=" + this.strayWrites;
+        + " strayWrites=" + this.strayWrites
+        + " waits=" + this.waits.size
+        + " waitsBegun=" + this.waitsBegun
+        + " waitsResolved=" + this.waitsResolved;
     },
   };
 
diff --git a/wxwidgets b/wxwidgets
index 6c33caf..1953c18 160000
--- a/wxwidgets
+++ b/wxwidgets
@@ -1 +1 @@
-Subproject commit 6c33cafa9c31fba99d4dae4b0d300183751d05dd
+Subproject commit 1953c18527e92204e1bbc957a90922f211937613