Merge candidate 20260908T070012Z-web-product

Change-source: pulse-maintainer

frontend-modern/browser-tests/lifecycle-control.md

@@ -137,3 +137,30 @@ not merely a larger timeout or successful CDP acknowledgements. No Pulse fixture
 installed convergence, destination receipt or release qualification was exercised.
 Complete output is retained in maintainer run `20260908T065015Z-web-product`,
 `headed-window-control.log`. Earlier failed controls remain relevant.
+
+## Native tab-switch control — 8 September 2026
+
+Run the same owned Xvfb command with `--headed-tab` instead of
+`--headed-window`. This does not request minimisation or require a window
+manager: it creates a second owned blank tab and activates it. Before freezing,
+it requires observed hidden → visible/focused → hidden states, each bounded to
+ten seconds with 250ms samples. It then uses the existing 2100ms host-side frozen
+wait, resumes while backgrounded, and activates the original tab. Ordered
+freeze/resume with unchanged ticks, a subsequent visible event, final focus and
+timer progress remain required. No synthetic visibility events or forced focus
+are used; no Playwright page session is attached.
+
+One run exited 0 on the same Chrome revision, Playwright and Node versions above,
+owned display :99. Preflight recorded hidden at tick 5, visible/focused at tick
+11, then hidden at tick 12. Freeze and resume both recorded tick 12.
+Post-resume remained hidden/unfocused at tick 12; tab activation produced a
+visible event and visible/focused state at tick 18. Complete runtime identities,
+intervention commands/responses and samples are retained in maintainer run
+`20260908T070012Z-web-product/headed-tab-control.log`.
+
+This establishes the positive control for the **tab-switch** mechanism, not
+window minimisation. Earlier adverse results and the default mode's unreliable
+250ms hidden-timer sample remain unchanged. No Pulse fixture or installed-pair
+acceptance ran. The next source-level convergence fixture must retain raw
+single-session ownership, the genuine background preflight, and the suspension
+probe rather than attach a Playwright page and assume equivalent behaviour.

scripts/check-browser-single-session-control.mjs

@@ -6,7 +6,8 @@ import { tmpdir } from 'node:os';
 import { join } from 'node:path';
 import { createRequire } from 'node:module';
 import { chromium } from '@playwright/test';
-const headedWindow = process.argv.includes('--headed-window');
+const headedTab = process.argv.includes('--headed-tab');
+const headedWindow = headedTab || process.argv.includes('--headed-window');
 const checkForeground = headedWindow || process.argv.includes('--foreground');
 if (headedWindow && !process.env.DISPLAY) throw new Error('--headed-window requires an owned X display');
 const wait = ms => new Promise(resolve => setTimeout(resolve, ms));
@@ -50,7 +51,7 @@ try {
   console.log(JSON.stringify({ browser: await send('Browser.getVersion'),
     playwright: require('@playwright/test/package.json').version, node: process.version,
     platform: process.platform, arch: process.arch, executable: chromium.executablePath(),
-    headedWindow, display: process.env.DISPLAY, observationBoundMs: headedWindow ? 10000 : 250 }));
+    headedWindow, headedTab, display: process.env.DISPLAY, observationBoundMs: headedWindow ? 10000 : 250 }));
   const results = [];
   // Preselected negative (focus forced) and positive (no forced focus), fresh targets.
   for (const focusEnabled of (headedWindow ? [false] : [true, false])) {
@@ -85,7 +86,28 @@ try {
       const snapshot = `({...window.probe, visibility: document.visibilityState, focus: document.hasFocus()})`;
       await wait(250);
       const before = await evaluate(snapshot);
-      if (headedWindow) {
+      let otherTarget;
+      const observe = async (stage, visibility) => {
+        const deadline = Date.now() + 10000;
+        let sample;
+        do {
+          await wait(250);
+          sample = await evaluate(snapshot);
+          console.log(JSON.stringify({ stage, snapshot: sample }));
+          if (sample.visibility === visibility && (visibility !== 'visible' || sample.focus)) return sample;
+        } while (Date.now() < deadline);
+        throw new Error(stage + ': native visibility transition not observed');
+      };
+      if (headedTab) {
+        assert.ok(before.visibility === 'visible' && before.focus, 'Tab baseline must be active');
+        otherTarget = (await windowCommand('Target.createTarget', { url: 'about:blank' })).targetId;
+        await windowCommand('Target.activateTarget', { targetId: otherTarget });
+        await observe('tab-background-preflight', 'hidden');
+        await windowCommand('Target.activateTarget', { targetId });
+        await observe('tab-foreground-preflight', 'visible');
+        await windowCommand('Target.activateTarget', { targetId: otherTarget });
+        await observe('tab-background-before-freeze', 'hidden');
+      } else if (headedWindow) {
         assert.ok(before.visibility === 'visible' && before.focus, 'Headed baseline must be visible and focused');
         await windowCommand('Browser.setWindowBounds', { windowId: windowInfo.windowId, bounds: { windowState: 'minimized' } });
         await wait(250);
@@ -103,7 +125,9 @@ try {
       // Resume is not foreground activation. Observe the two transitions separately.
       let foreground;
       if (checkForeground) {
-        if (headedWindow) {
+        if (headedTab) {
+          await windowCommand('Target.activateTarget', { targetId });
+        } else if (headedWindow) {
           await windowCommand('Browser.setWindowBounds', { windowId: windowInfo.windowId, bounds: { windowState: 'normal' } });
         }
         await command('Page.bringToFront', {});
@@ -117,6 +141,7 @@ try {
       }
       const result = { focusEnabled, before, after, foreground, commands, suspended };
       results.push(result); console.log(JSON.stringify(result));
+      if (otherTarget) await send('Target.closeTarget', { targetId: otherTarget });
     } finally { await send('Target.closeTarget', { targetId }); }
   }
   if (!headedWindow) assert.ok(!results[0].suspended && results[0].after.ticks - results[0].before.ticks >= 20,