From ad75228abeb6cb2b0f8737daa63f76a599f118f9 Mon Sep 17 00:00:00 2001
From: ciregenz <ciregenz@berkeley.edu>
Date: Thu, 4 Jun 2026 11:26:50 -0700
Subject: [PATCH] [eric] browser: guard capture-page on churning webviews to
 dodge the V8 crash

---
 electron/main.js                       | 16 ++++++++++++++--
 frontend/src/shared/browserRegistry.ts | 17 +++++++++++++++++
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/electron/main.js b/electron/main.js
index 5923a9d3..c5cc70b4 100644
--- a/electron/main.js
+++ b/electron/main.js
@@ -2206,8 +2206,20 @@ ipcMain.handle('install-update', async () => {
 });
 
 ipcMain.handle('capture-page', async (event, rect) => {
-  const image = await event.sender.capturePage(rect || undefined);
-  return image.toDataURL();
+  // Capturing a webContents whose GPU surface is mid-recycle (a webview navigating
+  // a heavy SPA) can crash the renderer (SharedImage 'non-existent mailbox' ->
+  // V8 ToLocalChecked). The caller now waits for webviews to settle, but guard
+  // here too: skip a gone/crashed/loading sender and never encode an empty image,
+  // returning null so the dashboard keeps its last good preview instead of dying.
+  try {
+    const wc = event.sender;
+    if (!wc || wc.isDestroyed() || wc.isCrashed() || wc.isLoading()) return null;
+    const image = await wc.capturePage(rect || undefined);
+    if (!image || image.isEmpty()) return null;
+    return image.toDataURL();
+  } catch {
+    return null;
+  }
 });
 
 ipcMain.handle('open-external', (_event, url) => {
diff --git a/frontend/src/shared/browserRegistry.ts b/frontend/src/shared/browserRegistry.ts
index 0305989e..8a03e481 100644
--- a/frontend/src/shared/browserRegistry.ts
+++ b/frontend/src/shared/browserRegistry.ts
@@ -23,6 +23,7 @@ export interface BrowserWebview extends HTMLElement {
   canGoForward: () => boolean;
   getURL: () => string;
   getTitle: () => string;
+  isLoading: () => boolean;
   capturePage: (rect?: { x: number; y: number; width: number; height: number }) => Promise<ElectronNativeImage>;
   executeJavaScript: (code: string) => Promise<any>;
   sendInputEvent: (event: any) => void;
@@ -64,3 +65,19 @@ export function findBrowserByWebContentsId(wcId: number): string | undefined {
   }
   return undefined;
 }
+
+// True if ANY registered webview is mid-navigation. Capturing the dashboard
+// (which composites live webview pixels) while a webview's GPU surface is being
+// recycled crashes the renderer (SharedImage 'non-existent mailbox' -> V8
+// ToLocalChecked), so the thumbnail capture must wait until they've settled.
+export function anyWebviewLoading(): boolean {
+  for (const wv of registry.values()) {
+    try {
+      if (typeof wv.isLoading === 'function' && wv.isLoading()) return true;
+    } catch {
+      // a torn-down webview can throw; treat as "not safe to capture"
+      return true;
+    }
+  }
+  return false;
+}