Desktop app hangs and crashes when rendering large session diff summary #33106

Environment

• App: OpenCode Desktop
• Version: 1.17.8
• Platform: macOS arm64
• Electron: 42.3.3
• Node: 24.15.0

Problem

OpenCode Desktop became unresponsive while opening/rendering an existing session, then crashed from the Electron main process.

The app first showed:

OpenCode is not responding
You can relaunch the app, open the logs, or keep waiting.

After choosing relaunch, Electron showed:

Uncaught Exception:
TypeError: Object has been destroyed
    at BrowserWindow.<anonymous> (.../app.asar/out/main/index.js:1268:76)
    at BrowserWindow.emit (node:events:509:28)
    at WebContents.<anonymous> (node:electron/js2c/browser_init:2:18806)
    at WebContents.emit (node:events:509:28)
    at .../app.asar/out/main/index.js:3322:11
    at process.processTicksAndRejections (node:internal/process/task_queues:104:5)

Evidence from redacted local inspection

The renderer unresponsive sampler pointed at timeline construction:

renderer unresponsive
at oc://renderer/assets/session-LOcZksCR.js:10169:53
at Array.some (<anonymous>)
at oc://renderer/assets/session-LOcZksCR.js:10169:18
at Proxy.reduceRight (<anonymous>)
at Object.constructMessageRows (oc://renderer/assets/session-LOcZksCR.js:10167:55)
at createTimelineProjection (oc://renderer/assets/session-LOcZksCR.js:10310:27)

I inspected the local SQLite state and found one user message with a very large summary.diffs payload:

summary.diffs count: 11878
summary.diffs size: about 6.88 MB
unique files: 11878

The relevant renderer code appears to deduplicate diffs with this pattern:

(userMessage.summary?.diffs ?? []).reduceRight((result, diff2) => {
  if (!isSummaryDiff(diff2)) return result;
  if (result.some((item) => item.file === diff2.file)) return result;
  result.push(diff2);
  return result;
}, []).reverse();

Because all files were unique, result.some(...) was close to a worst-case synchronous main-thread path.

The main-process crash appears to be a separate race during relaunch/window recovery: out/main/index.js:1268 accesses win.webContents.getURL() from the responsive handler after the BrowserWindow has already been destroyed.

Expected behavior

The desktop app should remain responsive even when a session has a large diff summary. Relaunching or recovering from an unresponsive renderer should not throw an uncaught main-process exception.

Actual behavior

The renderer hangs while constructing the timeline, then the main process can crash with TypeError: Object has been destroyed during relaunch/recovery.

Suggested fixes

• Use a Set-based linear pass for diff deduplication instead of result.some(...) inside reduceRight.
• Consider capping, lazy-rendering, or virtualizing very large summary.diffs payloads.
• Guard main-process event handlers before accessing win.webContents, e.g. check win.isDestroyed() and win.webContents.isDestroyed() in responsive, unresponsive, render-process-gone, and load-failure handlers.

Workaround

Clearing the oversized summary.diffs field for the affected local message allows the app to open again. I am not attaching the exported debug zip because it may contain local paths and session data, but I can provide redacted logs if needed.