diff --git a/playground/voyage-playground.html b/playground/voyage-playground.html
index 250fdef..fb0314d 100644
--- a/playground/voyage-playground.html
+++ b/playground/voyage-playground.html
@@ -540,9 +540,16 @@
     }
     .voyage-sidebar[aria-hidden="true"] .voyage-sidebar__panel { visibility: hidden; }
 
-    /* 2-state FAB toggle (per critical decision #4) */
+    /* 2-state FAB toggle (per critical decision #4).
+       v4.3 Step 3 — position: fixed so toggle stays reachable when the
+       sidebar carries aria-hidden="true" (finding 09132940 a11y).
+       The toggle is now a sibling of the <aside>, not a descendant,
+       so the aria-hidden subtree no longer hides the toggle from AT. */
     .voyage-fab {
-      position: relative;
+      position: fixed;
+      top: var(--space-3);
+      right: 4px;
+      z-index: 901;
       width: 32px;
       height: 32px;
       padding: 0;
@@ -962,6 +969,28 @@
     </section>
   </main>
 
+  <!-- v4.3 Step 3 (finding 09132940) — toggle button is a sibling of the
+       <aside aria-hidden="true"> so it remains exposed to AT regardless
+       of sidebar-hidden state. CSS .voyage-fab uses position: fixed
+       (z-index: 901) so it floats over the sidebar at all times. -->
+  <button
+    type="button"
+    id="voyage-sidebar-toggle"
+    class="voyage-fab"
+    data-action="toggle-sidebar"
+    aria-controls="voyage-sidebar"
+    aria-expanded="false"
+    aria-label="Skjul/vis annotation-panel"
+  >
+    <span
+      id="voyage-fab-badge"
+      class="voyage-fab__badge"
+      aria-live="polite"
+      aria-label="Antall drafts ventende"
+      hidden
+    >0</span>
+  </button>
+
   <!-- v4.3 Step 19 — sidebar-rail (hidden-by-default) with ordered annotation-list,
        filter (Alle/Åpne/Resolved), and jumplist count "X av N". Toggle via
        FAB data-action="toggle-sidebar" or ] keyboard shortcut (Step 20). -->
@@ -971,25 +1000,7 @@
     aria-label="Annotation drafts sidebar"
     aria-hidden="true"
   >
-    <div class="voyage-sidebar__rail">
-      <button
-        type="button"
-        id="voyage-sidebar-toggle"
-        class="voyage-fab"
-        data-action="toggle-sidebar"
-        aria-controls="voyage-sidebar"
-        aria-expanded="false"
-        aria-label="Skjul/vis annotation-panel"
-      >
-        <span
-          id="voyage-fab-badge"
-          class="voyage-fab__badge"
-          aria-live="polite"
-          aria-label="Antall drafts ventende"
-          hidden
-        >0</span>
-      </button>
-    </div>
+    <div class="voyage-sidebar__rail" aria-hidden="true"></div>
     <div class="voyage-sidebar__panel">
       <!-- v4.3 Step 19 — ordered annotation list with filter + jumplist count -->
       <div class="voyage-annotation-list" aria-label="Ordered annotation list">
diff --git a/tests/playground/voyage-playground.test.mjs b/tests/playground/voyage-playground.test.mjs
index e815aad..a9e85e7 100644
--- a/tests/playground/voyage-playground.test.mjs
+++ b/tests/playground/voyage-playground.test.mjs
@@ -483,6 +483,30 @@ test('voyage-playground.html renderArtifact strips comments before md.render (v4
   assert.ok(stripIdx > 0 && stripIdx < renderIdx, 'stripUnsafeComments must run before md.render');
 });
 
+// v4.3 Step 3 — sidebar-toggle button must be a sibling of <aside aria-hidden="true">,
+// not a descendant (finding 09132940 a11y). Hidden-state must not occlude the toggle.
+test('voyage-playground.html sidebar-toggle is outside aria-hidden region (v4.3 Step 3, finding 09132940)', () => {
+  const text = readFileSync(HTML, 'utf-8');
+  // Find the toggle button and the aside element by their unique anchors.
+  const toggleIdx = text.indexOf('id="voyage-sidebar-toggle"');
+  const asideIdx = text.indexOf('<aside\n    id="voyage-sidebar"');
+  // Fallback for single-line aside markup
+  const asideIdxAlt = text.indexOf('<aside id="voyage-sidebar"');
+  const asideAnchor = asideIdx > 0 ? asideIdx : asideIdxAlt;
+  assert.ok(toggleIdx > 0, 'voyage-sidebar-toggle must exist in HTML');
+  assert.ok(asideAnchor > 0, '<aside id="voyage-sidebar"> must exist in HTML');
+  // Toggle must precede the aside element textually
+  assert.ok(toggleIdx < asideAnchor,
+    'voyage-sidebar-toggle (idx ' + toggleIdx + ') must precede <aside id="voyage-sidebar"> (idx ' + asideAnchor + ')');
+  // Regression: slice between the button open-tag and its </button> close-tag,
+  // ensure no <aside element opens inside that slice (would mean the toggle
+  // is nested inside an aside).
+  const toggleBlockEnd = text.indexOf('</button>', toggleIdx);
+  assert.ok(toggleBlockEnd > toggleIdx, 'toggle button must have a </button> closer');
+  const toggleBlock = text.slice(toggleIdx, toggleBlockEnd);
+  assert.doesNotMatch(toggleBlock, /<aside\b/, 'toggle button must NOT contain a nested <aside element');
+});
+
 // v4.3 Step 1 — SC24-security defense in depth: renderArtifact bodyHtml is
 // sanitized via DOMPurify before DOM injection (finding 1d3591d4).
 test('voyage-playground.html renderArtifact sanitizes bodyHtml via DOMPurify (v4.3 Step 1, finding 1d3591d4)', () => {