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+/**
+ * E2E for #1204 — MESH LIVE panel renders detached/empty on Live Map page.
+ *
+ * Root symptom: `.live-header` inherits `flex-direction: column` from
+ * `.live-overlay` and PR #1180 added a sibling `.live-header-critical`
+ * strip + collapsible `.live-header-body`. With column direction the
+ * critical strip ("0 pkts" counter) renders ABOVE the title row, the
+ * panel collapses to one cropped column, and the stats row disappears.
+ *
+ * This test asserts a cohesive single-row header at desktop:
+ *   (a) `.live-header-critical` and `.live-title` overlap vertically
+ *       (same row, not stacked).
+ *   (b) `#livePktCount` pill is to the LEFT of (or at) `.live-title`,
+ *       and their Y-midpoints differ by < 8px.
+ *   (c) `.live-stats-row` is visible (height > 0, display ≠ none).
+ *   (d) `.live-feed .panel-content` exists and is a scrollable column
+ *       container — feed rows can render into it.
+ *
+ * Run: BASE_URL=http://localhost:13581 node test-issue-1204-live-panel-structure-e2e.js
+ */
+'use strict';
+const { chromium } = require('playwright');
+
+const BASE = process.env.BASE_URL || 'http://localhost:13581';
+
+let passed = 0, failed = 0;
+async function step(name, fn) {
+  try { await fn(); passed++; console.log('  ✓ ' + name); }
+  catch (e) { failed++; console.error('  ✗ ' + name + ': ' + e.message); }
+}
+function assert(c, m) { if (!c) throw new Error(m || 'assertion failed'); }
+
+async function gotoLive(page) {
+  await page.goto(BASE + '/#/live', { waitUntil: 'domcontentloaded' });
+  await page.waitForSelector('#liveHeader, .live-header', { timeout: 8000 });
+  await page.waitForTimeout(400);
+}
+
+(async () => {
+  const browser = await chromium.launch({
+    headless: true,
+    executablePath: process.env.CHROMIUM_PATH || undefined,
+    args: ['--no-sandbox', '--disable-gpu', '--disable-dev-shm-usage'],
+  });
+
+  console.log(`\n=== #1204 MESH LIVE panel cohesion E2E against ${BASE} ===`);
+
+  const ctx = await browser.newContext({ viewport: { width: 1440, height: 900 } });
+  const page = await ctx.newPage();
+  page.setDefaultTimeout(8000);
+  page.on('pageerror', (e) => console.error('[pageerror]', e.message));
+  await step('[1440x900] navigate to /live', async () => { await gotoLive(page); });
+
+  // (a) critical strip and title vertically overlap (same row, not stacked)
+  await step('[1440x900] .live-header-critical and .live-title share the same row', async () => {
+    const r = await page.evaluate(() => {
+      const crit = document.querySelector('.live-header-critical');
+      const title = document.querySelector('.live-title');
+      if (!crit || !title) return { found: false, crit: !!crit, title: !!title };
+      const a = crit.getBoundingClientRect();
+      const b = title.getBoundingClientRect();
+      return { found: true, a, b };
+    });
+    assert(r.found, `missing element (critical=${r.crit}, title=${r.title})`);
+    const overlap = Math.min(r.a.bottom, r.b.bottom) - Math.max(r.a.top, r.b.top);
+    assert(overlap > 0,
+      `critical strip and title must overlap vertically (same row); ` +
+      `critical Y=[${r.a.top},${r.a.bottom}], title Y=[${r.b.top},${r.b.bottom}]`);
+  });
+
+  // (b) pkt count pill is on the same baseline as the title (mid-Y delta < 8px)
+  await step('[1440x900] #livePktCount pill aligns horizontally with .live-title', async () => {
+    const r = await page.evaluate(() => {
+      const pkt = document.querySelector('#livePktCount');
+      const pill = pkt && pkt.closest('.live-stat-pill');
+      const title = document.querySelector('.live-title');
+      if (!pill || !title) return { found: false, pill: !!pill, title: !!title };
+      const a = pill.getBoundingClientRect();
+      const b = title.getBoundingClientRect();
+      return {
+        found: true,
+        midDelta: Math.abs((a.top + a.bottom) / 2 - (b.top + b.bottom) / 2),
+        pillBottom: a.bottom,
+        titleTop: b.top,
+      };
+    });
+    assert(r.found, `missing element (pill=${r.pill}, title=${r.title})`);
+    assert(r.midDelta < 8,
+      `pkt-count pill and title mid-Y must differ by < 8px (got ${r.midDelta.toFixed(1)}px); ` +
+      `bug repros as pill stacked above title`);
+  });
+
+  // (c) stats row is visible — height > 0 and display ≠ none
+  await step('[1440x900] .live-stats-row visible inside header', async () => {
+    const r = await page.evaluate(() => {
+      const row = document.querySelector('.live-stats-row');
+      if (!row) return { found: false };
+      const cs = getComputedStyle(row);
+      const rect = row.getBoundingClientRect();
+      return { found: true, display: cs.display, h: rect.height, w: rect.width };
+    });
+    assert(r.found, '.live-stats-row missing');
+    assert(r.display !== 'none', `.live-stats-row display must not be none (got ${r.display})`);
+    assert(r.h > 0 && r.w > 0,
+      `.live-stats-row must have nonzero size (got ${r.w}×${r.h}); ` +
+      `bug repros as stats clipped by max-height with column flex`);
+  });
+
+  // (d) feed panel-content is a scrollable column container — rows can render
+  await step('[1440x900] .live-feed .panel-content exists and is a column', async () => {
+    const r = await page.evaluate(() => {
+      const pc = document.querySelector('.live-feed .panel-content');
+      if (!pc) return { found: false };
+      const cs = getComputedStyle(pc);
+      const rect = pc.getBoundingClientRect();
+      return {
+        found: true,
+        display: cs.display,
+        flexDirection: cs.flexDirection,
+        overflowY: cs.overflowY,
+        h: rect.height,
+      };
+    });
+    assert(r.found, '.live-feed .panel-content missing — feed rows have nowhere to mount');
+    assert(r.display === 'flex',
+      `.live-feed .panel-content must be flex (got ${r.display})`);
+    assert(r.flexDirection === 'column',
+      `.live-feed .panel-content must be flex-direction column (got ${r.flexDirection})`);
+    assert(r.h > 0, `.live-feed .panel-content must have nonzero height (got ${r.h})`);
+  });
+
+  await ctx.close();
+  await browser.close();
+  console.log(`\n=== Results: passed ${passed} failed ${failed} ===`);
+  process.exit(failed > 0 ? 1 : 0);
+})().catch(e => { console.error(e); process.exit(1); });