diff --git a/frontend-modern/browser-tests/lifecycle-control.md b/frontend-modern/browser-tests/lifecycle-control.md
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+++ b/frontend-modern/browser-tests/lifecycle-control.md
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+# Browser suspension diagnostic
+
+Run `npm ci --ignore-scripts --no-audit --no-fund` at repository root, then
+`pulse-heavy-run -- node scripts/check-browser-lifecycle-control.mjs` using an
+installed Playwright Chromium. This uses owned blank pages only, no Pulse server
+or credentials. It is deliberately not wired into CI or release qualification.
+
+The comparison is fresh-session focus false versus true then false, each in a
+new context. Host-side waits avoid evaluating the frozen page. Success requires
+ordered freeze/resume events with identical timer counts and subsequent timer
+progress, not merely acknowledged protocol commands. Exit 1 means the
+intervention did not establish the control; it does not mean Pulse is broken.
+
+On 8 September 2026, Chromium 141.0.7390.37 / Playwright 1.56.1 / Node 24.20.0
+returned successful commands for both cases, but each advanced from 5 to 52
+ticks and remained visible/focused without lifecycle events. The intervention
+failed. No Pulse application was loaded and no incident-convergence assertion
+was exercised.
+
+The hypothesis came from the version-matched Chromium
+[emulation agent source](https://raw.githubusercontent.com/chromium/chromium/141.0.7390.37/third_party/blink/renderer/core/inspector/inspector_emulation_agent.cc):
+the equality guard in `setFocusEmulationEnabled` can skip updating the page on
+a fresh false request. Avoiding that guard did not establish suspension in
+this experiment. Do not continue treating that guard as a sufficient diagnosis.
+The next investigation must establish actual page visibility/lifecycle control
+under the automation harness before attempting Pulse recovery acceptance.
diff --git a/scripts/check-browser-lifecycle-control.mjs b/scripts/check-browser-lifecycle-control.mjs
new file mode 100644
index 000000000..405b6b4a9
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+++ b/scripts/check-browser-lifecycle-control.mjs
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+// Diagnostic only: proves a blank-page suspension control, not Pulse recovery.
+// Run through pulse-heavy-run -- node scripts/check-browser-lifecycle-control.mjs
+import assert from 'node:assert/strict';
+import { createRequire } from 'node:module';
+import { chromium } from '@playwright/test';
+
+const wait = (ms) => new Promise((resolve) => setTimeout(resolve, ms));
+const browser = await chromium.launch({ headless: true });
+try {
+  const require = createRequire(import.meta.url);
+  console.log(JSON.stringify({ browser: browser.version(),
+    playwright: require('@playwright/test/package.json').version,
+    node: process.version, platform: process.platform, arch: process.arch }));
+  const results = [];
+  // Preselected comparison; independent contexts prevent carry-over.
+  for (const transition of [false, true]) {
+    const context = await browser.newContext();
+    try {
+      const page = await context.newPage();
+      await page.evaluate(() => {
+        window.probe = { ticks: 0, events: [] };
+        setInterval(() => window.probe.ticks++, 50);
+        for (const type of ['freeze', 'resume', 'visibilitychange']) {
+          document.addEventListener(type, () => window.probe.events.push({
+            type, ticks: window.probe.ticks, visibility: document.visibilityState,
+          }));
+        }
+      });
+      const session = await context.newCDPSession(page);
+      const commands = [];
+      const send = async (method, params) => {
+        commands.push({ method, params, response: await session.send(method, params) });
+      };
+      if (transition) await send('Emulation.setFocusEmulationEnabled', { enabled: true });
+      await send('Emulation.setFocusEmulationEnabled', { enabled: false });
+      await wait(250);
+      const before = await page.evaluate(() => ({ ...window.probe,
+        visibility: document.visibilityState, focus: document.hasFocus() }));
+      await send('Page.setWebLifecycleState', { state: 'frozen' });
+      // Do not evaluate the page while frozen. Wait on the host instead.
+      await wait(2100);
+      await send('Page.setWebLifecycleState', { state: 'active' });
+      await wait(250);
+      const after = await page.evaluate(() => ({ ...window.probe,
+        visibility: document.visibilityState, focus: document.hasFocus() }));
+      const freeze = after.events.find((event) => event.type === 'freeze');
+      const resume = after.events.find((event) => event.type === 'resume');
+      const valid = Boolean(freeze && resume && freeze.ticks === resume.ticks &&
+        after.events.indexOf(freeze) < after.events.indexOf(resume) &&
+        after.ticks > resume.ticks);
+      const result = { transition, before, after, commands, valid };
+      results.push(result);
+      console.log(JSON.stringify(result));
+    } finally {
+      await context.close();
+    }
+  }
+  assert.ok(results[1].valid, 'true-to-false intervention did not establish suspension');
+} finally {
+  await browser.close();
+}