diff --git a/tests/playwright/site-full.spec.js b/tests/playwright/site-full.spec.js
index 8eb5ebf6..fa642caa 100644
--- a/tests/playwright/site-full.spec.js
+++ b/tests/playwright/site-full.spec.js
@@ -166,19 +166,22 @@ test('home', async ({ page }) => {
   }]);
 
   // Inject observer before page JS boots to detect hydration flash.
-  // A flash = the island content goes empty (0 children) between SSR and hydration.
-  // An atomic replaceChildren swap is fine — content is never visibly empty.
+  // A flash = the island's visible text content changes during hydration.
+  // True hydration should preserve SSR DOM — no visible change at all.
   await page.addInitScript(() => {
     window.__flashDetected = false;
+    window.__flashDetail = null;
     const check = () => {
       const stepper = document.querySelector('[data-sx-island="home/stepper"]');
       if (!stepper || !stepper.parentNode) return;
-      const ssrChildCount = stepper.childNodes.length;
+      const ssrText = stepper.textContent;
       new MutationObserver(() => {
-        if (stepper.childNodes.length === 0 && ssrChildCount > 0) {
+        const newText = stepper.textContent;
+        if (newText !== ssrText && !window.__flashDetected) {
           window.__flashDetected = true;
+          window.__flashDetail = { ssr: ssrText.substring(0, 80), hydrated: newText.substring(0, 80) };
         }
-      }).observe(stepper, { childList: true });
+      }).observe(stepper, { childList: true, subtree: true, characterData: true });
     };
     if (document.readyState === 'loading') {
       document.addEventListener('DOMContentLoaded', check);
@@ -204,9 +207,12 @@ test('home', async ({ page }) => {
   const noFlash = ssrIndex === hydratedIndex;
   entries.push({ ok: noFlash, label: `No flash: SSR=${ssrIndex} hydrated=${hydratedIndex} (cookie=7)`, feature: 'no-flash' });
 
-  // Check for hydration flash — island content going empty during hydration
-  const flashDetected = await page.evaluate(() => window.__flashDetected || false);
-  entries.push({ ok: !flashDetected, label: `No clobber: ${flashDetected ? 'island went empty during hydration' : 'clean'}`, feature: 'no-clobber' });
+  // Check for hydration flash — island text content changed during hydration
+  const flash = await page.evaluate(() => ({
+    detected: window.__flashDetected || false,
+    detail: window.__flashDetail,
+  }));
+  entries.push({ ok: !flash.detected, label: `No clobber: ${flash.detected ? 'text changed — ssr:"' + (flash.detail?.ssr || '').substring(0, 40) + '" → hydrated:"' + (flash.detail?.hydrated || '').substring(0, 40) + '"' : 'clean'}`, feature: 'no-clobber' });
 
   const info = await discoverPage(page);
   entries.push({ ok: true, label: 'Boot: data-sx-ready', feature: 'boot' });