Method getMemorySnapshot

browse/src/browser-manager.ts:1059–1150

* Diagnostic for `$B memory` and the /memory endpoint. * * Collects: * - Bun process memory (cross-platform, accurate, no shelling). * - Per-tab JS heap via CDP Performance.getMetrics — the most portable * per-tab signal CDP exposes. Misses native/GPU/Skia/cache memory *

(structures: MemoryStructureStats)

   * browser-manager doesn't take a hard dep on every buffer-owning module.
   */
  async getMemorySnapshot(structures: MemoryStructureStats): Promise<MemorySnapshot> {
    const bunMem = process.memoryUsage();
    const notes: string[] = [];

    // Per-tab JS heap. Lazy: only the pages we already track. A target
    // that died mid-snapshot is omitted, never throws.
    const tabs: MemoryTabSnapshot[] = [];
    for (const [id, page] of this.pages) {
      try {
        const url = (() => { try { return page.url(); } catch { return ''; } })();
        const title = await page.title().catch(() => '');
        const metrics = await withCdpSession(page, async (session) => {
          await session.send('Performance.enable').catch(() => undefined);
          const result = await session.send('Performance.getMetrics');
          return ((result as { metrics?: Array<{ name: string; value: number }> }).metrics) ?? [];
        });
        const mm: Record<string, number> = {};
        for (const m of metrics) mm[m.name] = m.value;
        tabs.push({
          id,
          url,
          title,
          jsHeapUsed: mm.JSHeapUsedSize ?? 0,
          jsHeapTotal: mm.JSHeapTotalSize ?? 0,
          documents: mm.Documents ?? 0,
          nodes: mm.Nodes ?? 0,
          listeners: mm.JSEventListeners ?? 0,
        });
      } catch {
        // Target died or CDP unavailable mid-snapshot — skip this tab.
      }
    }

    // Chromium process tree. Browser handle may be on the `browser` field
    // (launched mode) or accessible via `context.browser()` (persistent
    // context / headed mode); try both.
    let processes: MemoryProcess[] | null = null;
    const browser: Browser | null = this.browser ?? (this.context ? this.context.browser() : null);
    if (browser) {
      try {
        // `newBrowserCDPSession` is browser-wide. Not exposed on every
        // Playwright TypeScript surface, but present at runtime on the
        // Browser instance — use a typed cast to avoid the @ts-expect-error.
        type BrowserWithCDP = Browser & {
          newBrowserCDPSession?: () => Promise<{
            send: (method: string, params?: unknown) => Promise<unknown>;
            detach: () => Promise<void>;
          }>;
        };
        const maybeFactory = (browser as BrowserWithCDP).newBrowserCDPSession;
        if (typeof maybeFactory === 'function') {
          const browserSession = await maybeFactory.call(browser);
          try {
            const info = (await browserSession.send('SystemInfo.getProcessInfo')) as {
              processInfo?: Array<{ id: number; type: string; cpuTime: number }>;
            };
            processes = (info.processInfo ?? []).map((p) => ({
              id: p.id,