meshcore-analyzer/public/perf.js

/* === CoreScope — perf.js === */
'use strict';

var GH = 'https://github.com/Kpa-clawbot/corescope';

// detectPerfAnomalies — pure, testable.
// Computes per-component write rates over a rolling time window and flags any
// component whose current per-second rate exceeds `factor` × its rolling
// baseline rate. Issue #1120 acceptance: 5-minute window, 10× threshold.
//
// Inputs:
//   history: ordered array of snapshots [{ sampleAt: ISO, sources: { name: cum } }]
//   current: the freshest snapshot, same shape
//   opts:
//     windowMs       (default 5*60*1000) — rolling baseline window
//     factor         (default 10)        — rate-multiplier threshold
//     minHistorySec  (default 30)        — refuse to flag until baseline is stable
//
// Returns: { rates, baselineRates, flags } — all keyed by source name.
function detectPerfAnomalies(history, current, opts) {
  opts = opts || {};
  const windowMs = opts.windowMs || (5 * 60 * 1000);
  const factor = opts.factor || 10;
  const minHistorySec = opts.minHistorySec != null ? opts.minHistorySec : 30;
  const out = { rates: {}, baselineRates: {}, flags: {} };
  if (!current || !current.sources || !history || history.length === 0) return out;
  const curT = Date.parse(current.sampleAt);
  if (!isFinite(curT)) return out;

  // Find the most recent prior sample (for the *current* per-second rate)
  // and the oldest sample within the window (for the baseline).
  const prior = history[history.length - 1];
  const priorT = Date.parse(prior.sampleAt);
  const curDt = (curT - priorT) / 1000;
  if (!(curDt > 0)) return out;

  // Baseline: oldest sample within window vs. prior (the snapshot just before
  // `current`). Anything older than windowMs is excluded.
  const cutoff = curT - windowMs;
  let baseIdx = 0;
  for (let i = history.length - 1; i >= 0; i--) {
    if (Date.parse(history[i].sampleAt) < cutoff) { baseIdx = i + 1; break; }
  }
  if (baseIdx >= history.length) baseIdx = history.length - 1;
  const baseSnap = history[baseIdx];
  const baseT = Date.parse(baseSnap.sampleAt);
  const baseDt = (priorT - baseT) / 1000;

  // Compute rates for every source seen in current.
  for (const k of Object.keys(current.sources)) {
    const cur = current.sources[k] || 0;
    const prev = (prior.sources && prior.sources[k]) || 0;
    const rate = (cur - prev) / curDt;
    out.rates[k] = rate;
    if (baseDt <= 0 || baseDt < minHistorySec) {
      out.baselineRates[k] = null;
      continue;
    }
    const baseStart = (baseSnap.sources && baseSnap.sources[k]) || 0;
    const baseEnd = prev; // baseline window = [baseSnap .. prior]
    const baseRate = (baseEnd - baseStart) / baseDt;
    out.baselineRates[k] = baseRate;
    // Guard floor to avoid 0-baseline → infinite ratio false positives.
    const floor = 0.05; // 1 event per 20s minimum baseline
    if (rate > factor * Math.max(baseRate, floor) && rate > factor * floor) {
      out.flags[k] = true;
    }
  }
  return out;
}
if (typeof window !== 'undefined') {
  window.detectPerfAnomalies = detectPerfAnomalies;
}

function renderVersionCard(health) {
  if (!health || (!health.version && !health.commit)) return '';
  var ver = health.version && health.version !== 'unknown' ? health.version : null;
  var sha = health.commit && health.commit !== 'unknown' ? health.commit : null;
  if (!ver && !sha) return '';
  var vTag = ver ? (ver.charAt(0) === 'v' ? ver : 'v' + ver) : null;
  var parts = [];
  if (vTag) parts.push('<a href="' + GH + '/releases/tag/' + vTag + '" target="_blank" rel="noopener">' + vTag + '</a>');
  if (sha) parts.push('<a href="' + GH + '/commit/' + sha + '" target="_blank" rel="noopener">' + sha.slice(0, 7) + '</a>');
  return '<div class="perf-card"><div class="perf-num perf-num--small">' + parts.join(' · ') + '</div><div class="perf-label">Version</div></div>';
}

(function () {
  let interval = null;

  async function render(app) {
    app.innerHTML = '<div id="perfWrapper" style="padding:16px 24px;"><h2>⚡ Performance Dashboard</h2><div id="perfContent">Loading...</div></div>';
    await refresh();
  }

  async function refresh() {
    const el = document.getElementById('perfContent');
    if (!el) return;
    try {
      // #1258: /api/health was awaited AFTER Promise.all, adding a full RTT
      // (~50-200ms) on every 5s refresh. Issue it in parallel with the rest.
      const [server, client, ioStats, sqliteStats, writeSources, health] = await Promise.all([
        fetch('/api/perf').then(r => r.json()),
        Promise.resolve(window.apiPerf ? window.apiPerf() : null),
        fetch('/api/perf/io').then(r => r.json()).catch(() => null),
        fetch('/api/perf/sqlite').then(r => r.json()).catch(() => null),
        fetch('/api/perf/write-sources').then(r => r.json()).catch(() => null),
        fetch('/api/health').then(r => r.json()).catch(() => null)
      ]);

      let html = '';

      // Server overview
      html += `<div style="display:flex;gap:16px;flex-wrap:wrap;margin:16px 0;">
        <div class="perf-card"><div class="perf-num">${server.totalRequests}</div><div class="perf-label">Total Requests</div></div>
        <div class="perf-card"><div class="perf-num">${server.avgMs}ms</div><div class="perf-label">Avg Response</div></div>
        <div class="perf-card"><div class="perf-num">${health ? health.uptimeHuman : Math.round(server.uptime / 60) + 'm'}</div><div class="perf-label">Uptime</div></div>
        <div class="perf-card"><div class="perf-num">${server.slowQueries.length}</div><div class="perf-label">Slow (&gt;100ms)</div></div>
        ${renderVersionCard(health)}
      </div>`;

      // System health (memory, event loop / go runtime, WS)
      if (health) {
        const isGo = health.engine === 'go';
        if (isGo && server.goRuntime) {
          const gr = server.goRuntime;
          const gcColor = gr.lastPauseMs > 5 ? 'var(--status-red)' : gr.lastPauseMs > 1 ? 'var(--status-yellow)' : 'var(--status-green)';
          html += `<h3>🔧 Go Runtime</h3><div style="display:flex;gap:16px;flex-wrap:wrap;margin:8px 0;">
            <div class="perf-card"><div class="perf-num">${gr.goroutines}</div><div class="perf-label">Goroutines</div></div>
            <div class="perf-card"><div class="perf-num">${gr.numGC}</div><div class="perf-label">GC Collections</div></div>
            <div class="perf-card"><div class="perf-num" style="color:${gcColor}">${(+gr.pauseTotalMs).toFixed(1)}ms</div><div class="perf-label">GC Pause Total</div></div>
            <div class="perf-card"><div class="perf-num">${(+gr.lastPauseMs).toFixed(1)}ms</div><div class="perf-label">Last GC Pause</div></div>
            <div class="perf-card"><div class="perf-num">${(+gr.heapAllocMB).toFixed(1)}MB</div><div class="perf-label">Heap Alloc</div></div>
            <div class="perf-card"><div class="perf-num">${(+gr.heapSysMB).toFixed(1)}MB</div><div class="perf-label">Heap Sys</div></div>
            <div class="perf-card"><div class="perf-num">${(+gr.heapInuseMB).toFixed(1)}MB</div><div class="perf-label">Heap Inuse</div></div>
            <div class="perf-card"><div class="perf-num">${(+gr.heapIdleMB).toFixed(1)}MB</div><div class="perf-label">Heap Idle</div></div>
            <div class="perf-card"><div class="perf-num">${gr.numCPU}</div><div class="perf-label">CPUs</div></div>
            <div class="perf-card"><div class="perf-num">${health.websocket.clients}</div><div class="perf-label">WS Clients</div></div>
          </div>`;
        } else {
          const m = health.memory, el = health.eventLoop;
          const elColor = el.p95Ms > 500 ? 'var(--status-red)' : el.p95Ms > 100 ? 'var(--status-yellow)' : 'var(--status-green)';
          const memColor = m.heapUsed > m.heapTotal * 0.85 ? 'var(--status-red)' : m.heapUsed > m.heapTotal * 0.7 ? 'var(--status-yellow)' : 'var(--status-green)';
          html += `<h3>System Health</h3><div style="display:flex;gap:16px;flex-wrap:wrap;margin:8px 0;">
            <div class="perf-card"><div class="perf-num" style="color:${memColor}">${m.heapUsed}MB</div><div class="perf-label">Heap Used / ${m.heapTotal}MB</div></div>
            <div class="perf-card"><div class="perf-num">${m.rss}MB</div><div class="perf-label">RSS</div></div>
            <div class="perf-card"><div class="perf-num" style="color:${elColor}">${el.p95Ms}ms</div><div class="perf-label">Event Loop p95</div></div>
            <div class="perf-card"><div class="perf-num">${el.maxLagMs}ms</div><div class="perf-label">EL Max Lag</div></div>
            <div class="perf-card"><div class="perf-num">${el.currentLagMs}ms</div><div class="perf-label">EL Current</div></div>
            <div class="perf-card"><div class="perf-num">${health.websocket.clients}</div><div class="perf-label">WS Clients</div></div>
          </div>`;
        }
      }

      // Disk I/O (#1120)
      if (ioStats) {
        const fmtRate = (bps) => {
          if (bps >= 1048576) return (bps / 1048576).toFixed(1) + ' MB/s';
          if (bps >= 1024) return (bps / 1024).toFixed(1) + ' KB/s';
          return Math.round(bps) + ' B/s';
        };
        const writeWarn = ioStats.writeBytesPerSec > 10 * 1048576 ? ' ⚠️' : '';
        const cancelled = ioStats.cancelledWriteBytesPerSec || 0;
        // Cancelled writes warn at >1 MB/s — sustained cancellation usually
        // means truncate/unlink racing with active writers (#1119-shaped bug).
        const cancelledWarn = cancelled > 1048576 ? ' ⚠️' : '';
        html += `<h3>Disk I/O (server process)</h3><div style="display:flex;gap:16px;flex-wrap:wrap;margin:8px 0;">
          <div class="perf-card"><div class="perf-num">${fmtRate(ioStats.readBytesPerSec || 0)}</div><div class="perf-label">Read</div></div>
          <div class="perf-card"><div class="perf-num">${fmtRate(ioStats.writeBytesPerSec || 0)}${writeWarn}</div><div class="perf-label">Write</div></div>
          <div class="perf-card"><div class="perf-num">${fmtRate(cancelled)}${cancelledWarn}</div><div class="perf-label">Cancelled Write</div></div>
          <div class="perf-card"><div class="perf-num">${Math.round(ioStats.syscallsRead || 0)}/s</div><div class="perf-label">Syscalls Read</div></div>
          <div class="perf-card"><div class="perf-num">${Math.round(ioStats.syscallsWrite || 0)}/s</div><div class="perf-label">Syscalls Write</div></div>
        </div>`;

        // Ingestor row — sourced from ingestor's own /proc/self/io snapshot
        // surfaced via the stats file (#1120: "Both ingestor and server").
        if (ioStats.ingestor) {
          const ing = ioStats.ingestor;
          const ingWriteWarn = (ing.writeBytesPerSec || 0) > 10 * 1048576 ? ' ⚠️' : '';
          const ingCancelled = ing.cancelledWriteBytesPerSec || 0;
          const ingCancelledWarn = ingCancelled > 1048576 ? ' ⚠️' : '';
          html += `<h3>Disk I/O (Ingestor process)</h3><div style="display:flex;gap:16px;flex-wrap:wrap;margin:8px 0;">
            <div class="perf-card"><div class="perf-num">${fmtRate(ing.readBytesPerSec || 0)}</div><div class="perf-label">Read</div></div>
            <div class="perf-card"><div class="perf-num">${fmtRate(ing.writeBytesPerSec || 0)}${ingWriteWarn}</div><div class="perf-label">Write</div></div>
            <div class="perf-card"><div class="perf-num">${fmtRate(ingCancelled)}${ingCancelledWarn}</div><div class="perf-label">Cancelled Write</div></div>
            <div class="perf-card"><div class="perf-num">${Math.round(ing.syscallsRead || 0)}/s</div><div class="perf-label">Syscalls Read</div></div>
            <div class="perf-card"><div class="perf-num">${Math.round(ing.syscallsWrite || 0)}/s</div><div class="perf-label">Syscalls Write</div></div>
          </div>`;
        }
      }

      // Write Sources (#1120) — per-component counters from ingestor
      if (writeSources && writeSources.sources) {
        const src = writeSources.sources;
        const keys = Object.keys(src).sort((a, b) => (src[b] || 0) - (src[a] || 0));
        html += '<h3>Write Sources</h3>';
        if (keys.length === 0) {
          html += '<p style="color:var(--text-muted)">No ingestor stats yet (waiting for /tmp/corescope-ingestor-stats.json)</p>';
        } else {
          // Anomaly detection (#1120 acceptance): flag any component whose
          // per-second write rate exceeds 10× its 5-minute rolling baseline.
          // History is stashed on window so the detector has multi-sample
          // context across the 5s refresh tick.
          if (!window._perfWriteSourcesHistory) window._perfWriteSourcesHistory = [];
          const history = window._perfWriteSourcesHistory;
          const current = { sampleAt: writeSources.sampleAt || new Date().toISOString(), sources: { ...src } };
          const anom = detectPerfAnomalies(history, current, { windowMs: 5 * 60 * 1000, factor: 10 });
          // Append current and prune anything older than 6 minutes (keeps a
          // little headroom past the 5-min window, bounded memory).
          history.push(current);
          const cutoff = Date.parse(current.sampleAt) - (6 * 60 * 1000);
          while (history.length > 1 && Date.parse(history[0].sampleAt) < cutoff) history.shift();

          html += '<div style="overflow-x:auto"><table class="perf-table"><thead><tr><th scope="col">Source</th><th scope="col">Total</th><th scope="col">Rate/s</th><th scope="col">Baseline/s</th><th scope="col">Anomaly</th></tr></thead><tbody>';
          for (const k of keys) {
            const v = src[k] || 0;
            const rate = anom.rates[k];
            const base = anom.baselineRates[k];
            const flag = anom.flags[k] ? ' ⚠️' : '';
            const rateStr = (rate != null && isFinite(rate)) ? rate.toFixed(2) : '—';
            const baseStr = (base != null && isFinite(base)) ? base.toFixed(2) : '—';
            html += `<tr><td><code>${k}</code></td><td>${v.toLocaleString()}</td><td>${rateStr}</td><td>${baseStr}</td><td>${flag}</td></tr>`;
          }
          html += '</tbody></table></div>';
          if (writeSources.sampleAt) {
            html += `<div style="font-size:11px;color:var(--text-muted);margin-top:4px">Sampled: ${writeSources.sampleAt} · baseline window: 5 min · threshold: 10×</div>`;
          }
        }
      }

      // SQLite perf (separate from existing SQLite block — focused on WAL + cache hit) (#1120)
      if (sqliteStats) {
        const walMB = sqliteStats.walSizeMB || 0;
        const walFlag = walMB > 100 ? ' ⚠️' : '';
        const hitRate = (sqliteStats.cacheHitRate || 0) * 100;
        const hitFlag = hitRate > 0 && hitRate < 90 ? ' ⚠️' : '';
        html += `<h3>SQLite (WAL + Cache Hit)</h3><div style="display:flex;gap:16px;flex-wrap:wrap;margin:8px 0;">
          <div class="perf-card"><div class="perf-num">${walMB.toFixed(1)}MB${walFlag}</div><div class="perf-label">WAL Size</div></div>
          <div class="perf-card"><div class="perf-num">${(sqliteStats.pageCount || 0).toLocaleString()}</div><div class="perf-label">Page Count</div></div>
          <div class="perf-card"><div class="perf-num">${sqliteStats.pageSize || 0}</div><div class="perf-label">Page Size</div></div>
          <div class="perf-card"><div class="perf-num">${hitRate.toFixed(1)}%${hitFlag}</div><div class="perf-label">Cache Hit Rate</div></div>
        </div>`;
      }

      // Cache stats
      if (server.cache) {
        const c = server.cache;
        const clientCache = _apiCache ? _apiCache.size : 0;
        html += `<h3>Cache</h3><div style="display:flex;gap:16px;flex-wrap:wrap;margin:8px 0;">
          <div class="perf-card"><div class="perf-num">${c.size}</div><div class="perf-label">Server Entries</div></div>
          <div class="perf-card"><div class="perf-num">${c.hits}</div><div class="perf-label">Server Hits</div></div>
          <div class="perf-card"><div class="perf-num">${c.misses}</div><div class="perf-label">Server Misses</div></div>
          <div class="perf-card"><div class="perf-num" style="color:${c.hitRate > 50 ? 'var(--status-green)' : c.hitRate > 20 ? 'var(--status-yellow)' : 'var(--status-red)'}">${c.hitRate}%</div><div class="perf-label">Server Hit Rate</div></div>
          <div class="perf-card"><div class="perf-num">${c.staleHits || 0}</div><div class="perf-label">Stale Hits (SWR)</div></div>
          <div class="perf-card"><div class="perf-num">${c.recomputes || 0}</div><div class="perf-label">Recomputes</div></div>
          <div class="perf-card"><div class="perf-num">${clientCache}</div><div class="perf-label">Client Entries</div></div>
        </div>`;
        if (client) {
          html += `<div style="display:flex;gap:16px;flex-wrap:wrap;margin:8px 0;">
            <div class="perf-card"><div class="perf-num">${client.cacheHits || 0}</div><div class="perf-label">Client Hits</div></div>
            <div class="perf-card"><div class="perf-num">${client.cacheMisses || 0}</div><div class="perf-label">Client Misses</div></div>
            <div class="perf-card"><div class="perf-num" style="color:${(client.cacheHitRate||0) > 50 ? 'var(--status-green)' : 'var(--status-yellow)'}">${client.cacheHitRate || 0}%</div><div class="perf-label">Client Hit Rate</div></div>
          </div>`;
        }
      }

      // Packet Store stats
      if (server.packetStore) {
        const ps = server.packetStore;
        html += `<h3>In-Memory Packet Store</h3><div style="display:flex;gap:16px;flex-wrap:wrap;margin:8px 0;">
          <div class="perf-card"><div class="perf-num">${ps.inMemory.toLocaleString()}</div><div class="perf-label">Packets in RAM</div></div>
          <div class="perf-card"><div class="perf-num">${ps.trackedMB}MB</div><div class="perf-label">Tracked Memory</div></div>
          <div class="perf-card"><div class="perf-num">${ps.maxMB}MB</div><div class="perf-label">Memory Limit</div></div>
          <div class="perf-card"><div class="perf-num">${ps.estimatedMB}MB</div><div class="perf-label">Heap (debug)</div></div>
          <div class="perf-card"><div class="perf-num">${ps.queries.toLocaleString()}</div><div class="perf-label">Queries Served</div></div>
          <div class="perf-card"><div class="perf-num">${ps.inserts.toLocaleString()}</div><div class="perf-label">Live Inserts</div></div>
          <div class="perf-card"><div class="perf-num">${ps.evicted.toLocaleString()}</div><div class="perf-label">Evicted</div></div>
          <div class="perf-card"><div class="perf-num">${ps.indexes.byHash.toLocaleString()}</div><div class="perf-label">Unique Hashes</div></div>
          <div class="perf-card"><div class="perf-num">${ps.indexes.byObserver}</div><div class="perf-label">Observers</div></div>
          <div class="perf-card"><div class="perf-num">${ps.indexes.byNode.toLocaleString()}</div><div class="perf-label">Indexed Nodes</div></div>
        </div>`;
      }

      // SQLite stats
      if (server.sqlite && !server.sqlite.error) {
        const sq = server.sqlite;
        const walColor = sq.walSizeMB > 50 ? 'var(--status-red)' : sq.walSizeMB > 10 ? 'var(--status-yellow)' : 'var(--status-green)';
        const freelistColor = sq.freelistMB > 10 ? 'var(--status-yellow)' : 'var(--status-green)';
        html += `<h3>SQLite</h3><div style="display:flex;gap:16px;flex-wrap:wrap;margin:8px 0;">
          <div class="perf-card"><div class="perf-num">${sq.dbSizeMB}MB</div><div class="perf-label">DB Size</div></div>
          <div class="perf-card"><div class="perf-num" style="color:${walColor}">${sq.walSizeMB}MB</div><div class="perf-label">WAL Size</div></div>
          <div class="perf-card"><div class="perf-num" style="color:${freelistColor}">${sq.freelistMB}MB</div><div class="perf-label">Freelist</div></div>
          <div class="perf-card"><div class="perf-num">${(sq.rows.transmissions || 0).toLocaleString()}</div><div class="perf-label">Transmissions</div></div>
          <div class="perf-card"><div class="perf-num">${(sq.rows.observations || 0).toLocaleString()}</div><div class="perf-label">Observations</div></div>
          <div class="perf-card"><div class="perf-num">${sq.rows.nodes || 0}</div><div class="perf-label">Nodes</div></div>
          <div class="perf-card"><div class="perf-num">${sq.rows.observers || 0}</div><div class="perf-label">Observers</div></div>`;
        if (sq.walPages) {
          html += `<div class="perf-card"><div class="perf-num">${sq.walPages.busy}</div><div class="perf-label">WAL Busy Pages</div></div>`;
        }
        html += `</div>`;
      }

      // Server endpoints table — sort by total time (count * avg) DESC.
      // #1258: header claimed "sorted by total time" but JSON map order is
      // undefined and the frontend was not sorting. Slow endpoints could
      // appear anywhere in the table, defeating the section's whole purpose.
      const eps = Object.entries(server.endpoints).sort((a, b) => {
        const ta = (a[1].count || 0) * (a[1].avgMs || 0);
        const tb = (b[1].count || 0) * (b[1].avgMs || 0);
        return tb - ta;
      });
      if (eps.length) {
        html += '<h3>Server Endpoints (sorted by total time)</h3>';
        html += '<div style="overflow-x:auto"><table class="perf-table"><thead><tr><th scope="col">Endpoint</th><th scope="col">Count</th><th scope="col">Avg</th><th scope="col">P50</th><th scope="col">P95</th><th scope="col">Max</th><th scope="col">Total</th></tr></thead><tbody>';
        for (const [path, s] of eps) {
          const total = Math.round(s.count * s.avgMs);
          const cls = s.p95Ms > 200 ? ' class="perf-slow"' : s.p95Ms > 50 ? ' class="perf-warn"' : '';
          html += `<tr${cls}><td><code>${path}</code></td><td>${s.count}</td><td>${s.avgMs}ms</td><td>${s.p50Ms}ms</td><td>${s.p95Ms}ms</td><td>${s.maxMs}ms</td><td>${total}ms</td></tr>`;
        }
        html += '</tbody></table></div>';
      }

      // Client API calls
      if (client && client.endpoints.length) {
        html += '<h3>Client API Calls (this session)</h3>';
        html += '<div style="overflow-x:auto"><table class="perf-table"><thead><tr><th scope="col">Endpoint</th><th scope="col">Count</th><th scope="col">Avg</th><th scope="col">Max</th><th scope="col">Total</th></tr></thead><tbody>';
        for (const s of client.endpoints) {
          const cls = s.maxMs > 500 ? ' class="perf-slow"' : s.avgMs > 200 ? ' class="perf-warn"' : '';
          html += `<tr${cls}><td><code>${s.path}</code></td><td>${s.count}</td><td>${s.avgMs}ms</td><td>${s.maxMs}ms</td><td>${s.totalMs}ms</td></tr>`;
        }
        html += '</tbody></table></div>';
      }

      // Slow queries
      if (server.slowQueries.length) {
        html += '<h3>Recent Slow Queries (&gt;100ms)</h3>';
        html += '<div style="overflow-x:auto"><table class="perf-table"><thead><tr><th scope="col">Time</th><th scope="col">Path</th><th scope="col">Duration</th><th scope="col">Status</th></tr></thead><tbody>';
        for (const q of server.slowQueries.slice().reverse()) {
          html += `<tr class="perf-slow"><td>${new Date(q.time).toLocaleTimeString()}</td><td><code>${q.path}</code></td><td>${q.ms}ms</td><td>${q.status}</td></tr>`;
        }
        html += '</tbody></table></div>';
      }

      html += `<div style="margin-top:16px"><button id="perfReset" style="padding:8px 16px;cursor:pointer">Reset Stats</button> <button id="perfRefresh" style="padding:8px 16px;cursor:pointer">Refresh</button></div>`;
      el.innerHTML = html;

      document.getElementById('perfReset')?.addEventListener('click', async () => {
        await fetch('/api/perf/reset', { method: 'POST' });
        if (window._apiPerf) { window._apiPerf = { calls: 0, totalMs: 0, log: [] }; }
        refresh();
      });
      document.getElementById('perfRefresh')?.addEventListener('click', refresh);
    } catch (err) {
      el.innerHTML = `<p style="color:red">Error: ${err.message}</p>`;
    }
  }

  registerPage('perf', {
    init(app) {
      render(app);
      // #1258: don't burn CPU/network rebuilding the page (and its many cards
      // + 3 large tables) every 5s while the tab is hidden. Pause polling on
      // visibilitychange and resume on focus. Reduces background fetch traffic
      // to zero and prevents a returning user from seeing a 100+ms thrash as
      // a backlog of refreshes flush.
      const tick = () => {
        if (document.hidden) return;
        refresh();
      };
      interval = setInterval(tick, 5000);
      const onVis = () => {
        if (!document.hidden) refresh();
      };
      document.addEventListener('visibilitychange', onVis);
      this._onVis = onVis;
    },
    destroy() {
      if (interval) { clearInterval(interval); interval = null; }
      if (this._onVis) {
        document.removeEventListener('visibilitychange', this._onVis);
        this._onVis = null;
      }
    }
  });
})();