From 9210db4bd32bbfb9d0d17c5f784977febc547a0d Mon Sep 17 00:00:00 2001
From: Neil <4138956+nwparker@users.noreply.github.com>
Date: Wed, 2 Sep 2026 21:20:37 -0700
Subject: [PATCH] fix(crash-reporting): sample system memory before the
 renderer dies

---
 .../pre-gone-system-memory.test.ts            | 79 +++++++++++++++++++
 .../process-gone-diagnostics.ts               | 16 +++-
 2 files changed, 92 insertions(+), 3 deletions(-)
 create mode 100644 src/main/crash-reporting/pre-gone-system-memory.test.ts

diff --git a/src/main/crash-reporting/pre-gone-system-memory.test.ts b/src/main/crash-reporting/pre-gone-system-memory.test.ts
new file mode 100644
index 00000000000..76ef1cc86e3
--- /dev/null
+++ b/src/main/crash-reporting/pre-gone-system-memory.test.ts
@@ -0,0 +1,79 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import { setSystemMemoryInfoReaderForTest } from './gone-time-system-memory'
+import {
+  buildProcessGoneCrashDetails,
+  resetPreGoneProcessMetricsSamplingForTest,
+  samplePreGoneProcessMetrics
+} from './process-gone-diagnostics'
+
+type MetricFixture = {
+  pid: number
+  creationTime: number
+  type: string
+  memory: { workingSetSize: number; peakWorkingSetSize?: number; privateBytes?: number }
+}
+
+const { appMetricsMock } = vi.hoisted(() => ({
+  appMetricsMock: vi.fn<() => MetricFixture[]>(() => [])
+}))
+
+vi.mock('electron', () => ({ app: { getAppMetrics: appMetricsMock } }))
+
+const BROWSER_AND_RENDERER: MetricFixture[] = [
+  { pid: 10, creationTime: 1, type: 'Browser', memory: { workingSetSize: 1024 * 250 } },
+  {
+    pid: 11,
+    creationTime: 2,
+    type: 'Tab',
+    memory: { workingSetSize: 1024 * 400, peakWorkingSetSize: 1024 * 420, privateBytes: 1024 * 260 }
+  }
+]
+
+const BROWSER_ONLY: MetricFixture[] = [BROWSER_AND_RENDERER[0]]
+
+describe('pre-gone system memory', () => {
+  beforeEach(() => {
+    resetPreGoneProcessMetricsSamplingForTest()
+    setSystemMemoryInfoReaderForTest(null)
+    appMetricsMock.mockReturnValue(BROWSER_AND_RENDERER)
+  })
+
+  it('carries a pre-gone system-memory reading, not only the post-mortem one', () => {
+    // Windows commit pressure at sample time: 400 MB physical free, 200 MB commit left.
+    setSystemMemoryInfoReaderForTest(() => ({
+      total: 16_000 * 1024,
+      free: 400 * 1024,
+      swapTotal: 48_000 * 1024,
+      swapFree: 200 * 1024
+    }))
+    samplePreGoneProcessMetrics(Date.now() - 5_000)
+
+    // The renderer dies; its ~400 MB returns to the OS, so the gone-time read
+    // now shows a much healthier machine than the one that refused the alloc.
+    setSystemMemoryInfoReaderForTest(() => ({
+      total: 16_000 * 1024,
+      free: 3_000 * 1024,
+      swapTotal: 48_000 * 1024,
+      swapFree: 2_900 * 1024
+    }))
+    appMetricsMock.mockReturnValue(BROWSER_ONLY)
+
+    const details = buildProcessGoneCrashDetails({ processType: 'renderer' }, 'renderer')
+
+    expect(details.systemMemorySwapFreeMB).toBe(2_900)
+    expect(details.processMetricsPreGoneSystemMemorySwapFreeMB).toBe(200)
+    expect(details.processMetricsPreGoneSystemMemoryFreeMB).toBe(400)
+    expect(details.processMetricsPreGoneSystemMemoryTotalMB).toBe(16_000)
+  })
+
+  it('leaves the pre-gone sample free of system-memory keys when the reading is unavailable', () => {
+    samplePreGoneProcessMetrics(Date.now() - 5_000)
+
+    const details = buildProcessGoneCrashDetails({ processType: 'renderer' }, 'renderer')
+
+    expect(details.processMetricsPreGoneRendererWorkingSetMB).toBe(400)
+    expect(
+      Object.keys(details).filter((key) => key.startsWith('processMetricsPreGoneSystemMemory'))
+    ).toEqual([])
+  })
+})
diff --git a/src/main/crash-reporting/process-gone-diagnostics.ts b/src/main/crash-reporting/process-gone-diagnostics.ts
index d0bb380a2b6..8070be3ae22 100644
--- a/src/main/crash-reporting/process-gone-diagnostics.ts
+++ b/src/main/crash-reporting/process-gone-diagnostics.ts
@@ -195,7 +195,9 @@ export function samplePreGoneProcessMetrics(nowMs: number = Date.now()): void {
   try {
     const metrics = app.getAppMetrics()
     preGoneSample = {
-      details: collectProcessGoneMetricDetails(metrics),
+      // Why: the gone-time system read happens after the corpse released its
+      // pages, so only a live sample can show the pressure that refused the alloc.
+      details: { ...collectProcessGoneMetricDetails(metrics), ...getSystemMemoryAtGoneDetails() },
       processes: sampledProcessIdentities(metrics),
       sampledAtMs: nowMs
     }
@@ -225,6 +227,15 @@ export function resetPreGoneProcessMetricsSamplingForTest(): void {
 
 const PROCESS_METRICS_KEY_PREFIX = 'processMetrics'
 
+// Why: the sample now mixes processMetrics* and systemMemory* keys; only the
+// former carries the prefix to strip, the latter just needs title-casing.
+function preGoneDetailKey(key: string): string {
+  const suffix = key.startsWith(PROCESS_METRICS_KEY_PREFIX)
+    ? key.slice(PROCESS_METRICS_KEY_PREFIX.length)
+    : `${key.charAt(0).toUpperCase()}${key.slice(1)}`
+  return `${PROCESS_METRICS_KEY_PREFIX}PreGone${suffix}`
+}
+
 function preGoneSampleDetails(
   sample: PreGoneProcessMetricsSample,
   nowMs: number
@@ -236,8 +247,7 @@ function preGoneSampleDetails(
     processMetricsPreGoneCrashedProcessAttributionAmbiguous: true
   }
   for (const [key, value] of Object.entries(sample.details)) {
-    details[`${PROCESS_METRICS_KEY_PREFIX}PreGone${key.slice(PROCESS_METRICS_KEY_PREFIX.length)}`] =
-      value
+    details[preGoneDetailKey(key)] = value
   }
   return details
 }