diff --git a/web/tests/integration/account-startup-profile.mjs b/web/tests/integration/account-startup-profile.mjs
new file mode 100644
index 0000000..73048ed
--- /dev/null
+++ b/web/tests/integration/account-startup-profile.mjs
@@ -0,0 +1,117 @@
+import { chromium, expect } from "@playwright/test";
+import { mkdir, writeFile } from "node:fs/promises";
+const output =
+  process.env.NOTES_UI_OUTPUT ?? "test-results/account-startup-profile";
+const targets = [
+  {
+    name: "baseline",
+    url: process.env.NOTES_BASELINE_URL ?? "http://127.0.0.1:5184/",
+  },
+  {
+    name: "candidate",
+    url: process.env.NOTES_CANDIDATE_URL ?? "http://127.0.0.1:5185/",
+  },
+];
+await mkdir(output, { recursive: true });
+const browser = await chromium.launch({ channel: "chrome", headless: true });
+const samples = [];
+try {
+  // Fixed alternating order before observing results; no retry-until-green.
+  for (let pair = 0; pair < 10; pair++) {
+    const ordered = pair % 2 ? [...targets].reverse() : targets;
+    for (const target of ordered) {
+      const context = await browser.newContext({
+        viewport: { width: 1160, height: 850 },
+        serviceWorkers: "block",
+      });
+      await context.addInitScript(() => {
+        window.__accountStartupProbe = { lcp: null, cls: 0 };
+        new PerformanceObserver((list) => {
+          for (const entry of list.getEntries())
+            window.__accountStartupProbe.lcp = entry.startTime;
+        }).observe({ type: "largest-contentful-paint", buffered: true });
+        new PerformanceObserver((list) => {
+          for (const entry of list.getEntries())
+            if (!entry.hadRecentInput)
+              window.__accountStartupProbe.cls += entry.value;
+        }).observe({ type: "layout-shift", buffered: true });
+      });
+      const page = await context.newPage(),
+        errors = [];
+      page.on("pageerror", (error) => errors.push(error.message));
+      try {
+        await page.goto(target.url);
+        await expect(page.locator(".account-card h1")).toBeVisible();
+        const readyMs = await page.evaluate(() => performance.now());
+        await page.locator(".account-page").evaluate(async (element) => {
+          await document.fonts.ready;
+          await Promise.all(
+            element
+              .getAnimations({ subtree: true })
+              .filter(
+                (animation) =>
+                  animation.effect?.getTiming().iterations !== Infinity,
+              )
+              .map((animation) => animation.finished.catch(() => {})),
+          );
+          for (let i = 0; i < 12; i++) await new Promise(requestAnimationFrame);
+        });
+        const sample = await page.evaluate(() => window.__accountStartupProbe);
+        expect(sample.lcp).not.toBe(null);
+        expect(sample.lcp).toBeLessThan(2500);
+        expect(sample.cls).toBe(0);
+        expect(errors).toEqual([]);
+        samples.push({
+          pair,
+          target: target.name,
+          lcpMs: sample.lcp,
+          cls: sample.cls,
+          accountReadyMs: +readyMs.toFixed(2),
+        });
+      } finally {
+        await context.close();
+      }
+    }
+  }
+  const median = (values) => {
+    const ordered = [...values].sort((a, b) => a - b);
+    const middle = Math.floor(ordered.length / 2);
+    return (ordered[middle - 1] + ordered[middle]) / 2;
+  };
+  const baselineMedian = median(
+    samples
+      .filter((sample) => sample.target === "baseline")
+      .map((sample) => sample.lcpMs),
+  );
+  const candidateMedian = median(
+    samples
+      .filter((sample) => sample.target === "candidate")
+      .map((sample) => sample.lcpMs),
+  );
+  const result = {
+    qualified:
+      "Production static account-entry startup only, empty disposable browser profiles; blocked service workers, no authentication/backend operation, no native/signed-in/Search/animation acceptance claim",
+    browser: browser.version(),
+    samples,
+    baselineMedianLcpMs: baselineMedian,
+    candidateMedianLcpMs: candidateMedian,
+    medianDifferenceMs: candidateMedian - baselineMedian,
+    target2500msAndZeroClsPassed: true,
+    comparison:
+      "Fixed10alternating pairs; raw timing variation retained, no strict no-regression conclusion from noisy samples alone",
+  };
+  await writeFile(`${output}/result.json`, JSON.stringify(result, null, 2));
+  console.log(
+    JSON.stringify({
+      baselineMedian,
+      candidateMedian,
+      samples: samples.length,
+      target2500msAndZeroClsPassed: true,
+    }),
+  );
+} catch (error) {
+  await writeFile(`${output}/failure.txt`, String(error));
+  throw error;
+} finally {
+  await browser.close();
+}