Improve attachment memory safety, downloads, and high-memory alert UX.

Stream large receives to disk with chunk acks to cap renderer RAM, evict
off-screen display blobs, and route exports through a disk-aware download
service. Fix the high-memory dialog (backdrop dismiss, copy, log actions),
allow diagnostics paths in the path jail, and restore persisted image
hydration after reload.

Co-authored-by: Cursor <cursoragent@cursor.com>

electron/diagnostics/diagnostics.lifecycle.ts

@@ -10,19 +10,21 @@ import { resolveReadablePath } from '../path-jail';
 import { sumWorkingSetKb } from './process-metrics.rules';
 import { isPerfDiagEnabled } from './diagnostics.flags';
 import { exceedsHighMemoryThreshold } from './high-memory-alert.rules';
-import { buildHighMemoryDiagnosticPayload } from './high-memory-snapshot.rules';
-import { collectImmediateRendererSamples } from './immediate-renderer-samples.collector';
+import { captureHighMemoryDiagnostics } from './high-memory-capture';
 import { collectSessionContext } from './session-context.collector';
 import {
   clearHighMemoryAlert,
   readHighMemoryAlert,
-  writeHighMemoryAlert
+  writeHighMemoryAlert,
+  type HighMemoryAlertRecord
 } from './high-memory-alert.store';
 import type { PerfDiagEntry } from './diagnostics.models';
 import { PerfDiagWriter } from './diagnostics.writer';
 
 const PROCESS_POLL_INTERVAL_MS = 5_000;
 
+export const HIGH_MEMORY_ALERT_PENDING_CHANNEL = 'high-memory-alert-pending';
+
 let activeWriter: PerfDiagWriter | null = null;
 let processPollTimer: NodeJS.Timeout | null = null;
 let diagnosticsEnabled = false;
@@ -67,6 +69,24 @@ export function ensurePerfDiagIpcRegistered(): void {
     return true;
   });
 
+  ipcMain.handle('export-high-memory-diagnostics', async () => {
+    const metrics = collectAppMetricsSnapshot();
+    const totalKb = sumWorkingSetKb(metrics.processes) ?? 0;
+    const record = await captureHighMemoryDiagnostics({
+      userDataPath: app.getPath('userData'),
+      sessionStartedAt,
+      metrics,
+      totalWorkingSetKb: totalKb,
+      writer: activeWriter,
+      mainWindow: getMainWindow(),
+      reason: 'manual'
+    });
+
+    await persistAndNotifyHighMemoryAlert(record);
+
+    return record;
+  });
+
   ipcMain.handle('show-log-file-in-folder', async (_event, filePath: string) => {
     if (typeof filePath !== 'string' || !filePath.trim()) {
       return {
@@ -94,8 +114,48 @@ export function getActivePerfDiagWriter(): PerfDiagWriter | null {
   return activeWriter;
 }
 
+export function startHighMemoryMonitoring(): void {
+  ensurePerfDiagIpcRegistered();
+
+  if (!sessionStartedAt) {
+    sessionStartedAt = Date.now();
+    highMemoryAlertTriggeredThisSession = false;
+  }
+
+  if (processPollTimer) {
+    return;
+  }
+
+  const sample = (): void => {
+    try {
+      const metrics = collectAppMetricsSnapshot();
+      const totalKb = sumWorkingSetKb(metrics.processes);
+
+      if (activeWriter && diagnosticsEnabled) {
+        activeWriter.append({
+          collectedAt: metrics.collectedAt,
+          source: 'main',
+          type: 'process',
+          payload: {
+            totalWorkingSetKb: totalKb,
+            processes: metrics.processes
+          }
+        });
+      }
+
+      void maybeTriggerHighMemoryAlert(metrics, totalKb);
+    } catch {
+      // Collector failures must never affect the app.
+    }
+  };
+
+  sample();
+  processPollTimer = setInterval(sample, PROCESS_POLL_INTERVAL_MS);
+}
+
 export function startPerfDiagnostics(): PerfDiagWriter | null {
   ensurePerfDiagIpcRegistered();
+  startHighMemoryMonitoring();
   diagnosticsEnabled = isPerfDiagEnabled(process.env, app.isPackaged);
 
   if (!diagnosticsEnabled) {
@@ -109,10 +169,7 @@ export function startPerfDiagnostics(): PerfDiagWriter | null {
   });
 
   activeWriter = writer;
-  highMemoryAlertTriggeredThisSession = false;
-  sessionStartedAt = Date.now();
   registerProcessCrashHandlers(writer);
-  startProcessMetricsPolling(writer);
 
   const userDataPath = app.getPath('userData');
 
@@ -188,14 +245,15 @@ export async function shutdownPerfDiagnostics(): Promise<void> {
   }
 
   await activeWriter.flushSnapshot('shutdown');
+  activeWriter = null;
+  diagnosticsEnabled = false;
+}
 
+export function shutdownHighMemoryMonitoring(): void {
   if (processPollTimer) {
     clearInterval(processPollTimer);
     processPollTimer = null;
   }
-
-  activeWriter = null;
-  diagnosticsEnabled = false;
 }
 
 function registerProcessCrashHandlers(writer: PerfDiagWriter): void {
@@ -241,34 +299,7 @@ function registerProcessCrashHandlers(writer: PerfDiagWriter): void {
   });
 }
 
-function startProcessMetricsPolling(writer: PerfDiagWriter): void {
-  const sample = (): void => {
-    try {
-      const metrics = collectAppMetricsSnapshot();
-      const totalKb = sumWorkingSetKb(metrics.processes);
-
-      writer.append({
-        collectedAt: metrics.collectedAt,
-        source: 'main',
-        type: 'process',
-        payload: {
-          totalWorkingSetKb: totalKb,
-          processes: metrics.processes
-        }
-      });
-
-      void maybeTriggerHighMemoryAlert(writer, metrics, totalKb);
-    } catch {
-      // Collector failures must never affect the app.
-    }
-  };
-
-  sample();
-  processPollTimer = setInterval(sample, PROCESS_POLL_INTERVAL_MS);
-}
-
 async function maybeTriggerHighMemoryAlert(
-  writer: PerfDiagWriter,
   metrics: AppMetricsSnapshot,
   totalWorkingSetKb: number | null
 ): Promise<void> {
@@ -278,51 +309,26 @@ async function maybeTriggerHighMemoryAlert(
 
   highMemoryAlertTriggeredThisSession = true;
 
-  const detectedAt = Date.now();
-  const userDataPath = app.getPath('userData');
-  const immediateRendererEntries = await collectImmediateRendererSamples(getMainWindow());
-  const environment = collectSessionContext({
+  const record = await captureHighMemoryDiagnostics({
+    userDataPath: app.getPath('userData'),
     sessionStartedAt,
-    userDataPath
+    metrics,
+    totalWorkingSetKb: totalWorkingSetKb ?? 0,
+    writer: activeWriter,
+    mainWindow: getMainWindow(),
+    reason: 'threshold'
   });
 
-  for (const entry of immediateRendererEntries) {
-    writer.append(entry);
-  }
+  await persistAndNotifyHighMemoryAlert(record);
+}
 
-  writer.append({
-    collectedAt: detectedAt,
-    source: 'main',
-    type: 'environment',
-    payload: {
-      ...environment
-    }
-  });
+async function persistAndNotifyHighMemoryAlert(record: HighMemoryAlertRecord): Promise<void> {
+  await writeHighMemoryAlert(app.getPath('userData'), record);
+  notifyHighMemoryAlert(record);
+}
 
-  writer.append({
-    collectedAt: detectedAt,
-    source: 'main',
-    type: 'high-memory',
-    payload: buildHighMemoryDiagnosticPayload({
-      detectedAt,
-      totalWorkingSetKb: totalWorkingSetKb ?? 0,
-      metrics,
-      environment,
-      mainProcessMemory: process.memoryUsage(),
-      ringEntries: writer.bufferedEntries,
-      immediateRendererEntries,
-      sessionId: writer.sessionId
-    })
-  });
-
-  await writer.flushSnapshot('high-memory-threshold');
-
-  await writeHighMemoryAlert(userDataPath, {
-    logFilePath: writer.snapshotFilePath,
-    detectedAt,
-    peakWorkingSetKb: totalWorkingSetKb ?? 0,
-    sessionId: writer.sessionId
-  });
+function notifyHighMemoryAlert(record: HighMemoryAlertRecord): void {
+  getMainWindow()?.webContents.send(HIGH_MEMORY_ALERT_PENDING_CHANNEL, record);
 }
 
 function normalizeRendererEntry(entry: PerfDiagEntry): PerfDiagEntry {

electron/diagnostics/high-memory-alert.store.spec.ts

@@ -33,7 +33,8 @@ describe('high-memory-alert.store', () => {
       logFilePath: path.join(userDataPath, 'diagnostics', 'perf-session.jsonl'),
       detectedAt: 1_700_000_000_000,
       peakWorkingSetKb: 2_200_000,
-      sessionId: 'session-1'
+      sessionId: 'session-1',
+      reason: 'threshold' as const
     };
 
     await writeHighMemoryAlert(userDataPath, record);

electron/diagnostics/high-memory-alert.store.ts

@@ -1,11 +1,14 @@
 import * as fsp from 'fs/promises';
 import * as path from 'path';
 
+export type HighMemoryAlertReason = 'manual' | 'threshold';
+
 export interface HighMemoryAlertRecord {
   logFilePath: string;
   detectedAt: number;
   peakWorkingSetKb: number;
   sessionId: string;
+  reason?: HighMemoryAlertReason;
 }
 
 export function resolveHighMemoryAlertPath(userDataPath: string): string {
@@ -31,7 +34,10 @@ export async function readHighMemoryAlert(userDataPath: string): Promise<HighMem
       logFilePath: parsed.logFilePath,
       detectedAt: parsed.detectedAt,
       peakWorkingSetKb: parsed.peakWorkingSetKb,
-      sessionId: parsed.sessionId
+      sessionId: parsed.sessionId,
+      ...(parsed.reason === 'manual' || parsed.reason === 'threshold'
+        ? { reason: parsed.reason }
+        : {})
     };
   } catch {
     return null;

electron/diagnostics/high-memory-capture.spec.ts

@@ -0,0 +1,57 @@
+import {
+  beforeEach,
+  describe,
+  expect,
+  it,
+  vi
+} from 'vitest';
+import * as os from 'os';
+import * as path from 'path';
+import * as fsp from 'fs/promises';
+
+import { captureHighMemoryDiagnostics } from './high-memory-capture';
+
+vi.mock('./immediate-renderer-samples.collector', () => ({
+  collectImmediateRendererSamples: vi.fn(async () => [])
+}));
+
+vi.mock('./session-context.collector', () => ({
+  collectSessionContext: vi.fn(() => ({
+    platform: 'linux',
+    userDataPath: '/tmp/user-data'
+  }))
+}));
+
+describe('captureHighMemoryDiagnostics', () => {
+  let userDataPath = '';
+
+  beforeEach(async () => {
+    userDataPath = await fsp.mkdtemp(path.join(os.tmpdir(), 'metoyou-high-memory-capture-'));
+  });
+
+  it('writes a diagnostics snapshot and returns an alert record', async () => {
+    const record = await captureHighMemoryDiagnostics({
+      userDataPath,
+      sessionStartedAt: Date.now() - 60_000,
+      metrics: {
+        collectedAt: Date.now(),
+        processes: [
+          {
+            pid: 1,
+            type: 'Browser',
+            workingSetKb: 2_200_000
+          }
+        ]
+      },
+      totalWorkingSetKb: 2_200_000,
+      writer: null,
+      mainWindow: null,
+      reason: 'manual'
+    });
+
+    expect(record.peakWorkingSetKb).toBe(2_200_000);
+    expect(record.reason).toBe('manual');
+    expect(record.logFilePath).toContain(userDataPath);
+    await expect(fsp.stat(record.logFilePath)).resolves.toBeDefined();
+  });
+});

electron/diagnostics/high-memory-capture.ts

@@ -0,0 +1,80 @@
+import type { BrowserWindow } from 'electron';
+import type { AppMetricsSnapshot } from '../app-metrics';
+import { buildHighMemoryDiagnosticPayload } from './high-memory-snapshot.rules';
+import { collectImmediateRendererSamples } from './immediate-renderer-samples.collector';
+import { collectSessionContext } from './session-context.collector';
+import type { HighMemoryAlertRecord } from './high-memory-alert.store';
+import type { PerfDiagEntry } from './diagnostics.models';
+import { PerfDiagWriter } from './diagnostics.writer';
+
+export type HighMemoryCaptureReason = 'manual' | 'threshold';
+
+export interface CaptureHighMemoryDiagnosticsInput {
+  userDataPath: string;
+  sessionStartedAt: number;
+  metrics: AppMetricsSnapshot;
+  totalWorkingSetKb: number;
+  writer: PerfDiagWriter | null;
+  mainWindow: BrowserWindow | null;
+  reason: HighMemoryCaptureReason;
+}
+
+export async function captureHighMemoryDiagnostics(
+  input: CaptureHighMemoryDiagnosticsInput
+): Promise<HighMemoryAlertRecord> {
+  const detectedAt = Date.now();
+  const writer = input.writer ?? new PerfDiagWriter({
+    userDataPath: input.userDataPath,
+    sessionId: `${input.reason}-${detectedAt.toString(36)}-${process.pid}`
+  });
+  const immediateRendererEntries = await collectImmediateRendererSamples(input.mainWindow);
+  const environment = collectSessionContext({
+    sessionStartedAt: input.sessionStartedAt,
+    userDataPath: input.userDataPath
+  });
+
+  appendEntries(writer, immediateRendererEntries);
+  appendEntries(writer, [
+    {
+      collectedAt: detectedAt,
+      source: 'main',
+      type: 'environment',
+      payload: {
+        ...environment
+      }
+    },
+    {
+      collectedAt: detectedAt,
+      source: 'main',
+      type: 'high-memory',
+      payload: buildHighMemoryDiagnosticPayload({
+        detectedAt,
+        totalWorkingSetKb: input.totalWorkingSetKb,
+        metrics: input.metrics,
+        environment,
+        mainProcessMemory: process.memoryUsage(),
+        ringEntries: writer.bufferedEntries,
+        immediateRendererEntries,
+        sessionId: writer.sessionId
+      })
+    }
+  ]);
+
+  await writer.flushSnapshot(
+    input.reason === 'manual' ? 'manual-export' : 'high-memory-threshold'
+  );
+
+  return {
+    logFilePath: writer.snapshotFilePath,
+    detectedAt,
+    peakWorkingSetKb: input.totalWorkingSetKb,
+    sessionId: writer.sessionId,
+    reason: input.reason
+  };
+}
+
+function appendEntries(writer: PerfDiagWriter, entries: readonly PerfDiagEntry[]): void {
+  for (const entry of entries) {
+    writer.append(entry);
+  }
+}

electron/diagnostics/index.ts

@@ -15,8 +15,11 @@ export {
   attachRendererDiagnosticsHooks,
   ensurePerfDiagIpcRegistered,
   getActivePerfDiagWriter,
+  HIGH_MEMORY_ALERT_PENDING_CHANNEL,
   isPerfDiagActive,
+  shutdownHighMemoryMonitoring,
   shutdownPerfDiagnostics,
+  startHighMemoryMonitoring,
   startPerfDiagnostics
 } from './diagnostics.lifecycle';
 export type { PerfDiagEntry, PerfDiagEntryType, PerfDiagSource } from './diagnostics.models';