GitHub Copilot constantly freezes for several seconds in long chats.

This is really a regression of #285251 . Or maybe #285251 was never fixed. I haven't seen it for a while because I haven't been working with long chats.

In any case the point is that as the chat grows longer, suddenly typing starts freezes every minute or so. It's a stop-the-world event where everything is frozen for several seconds.

Currently the size of my chat "**Copy All** and save as Markdown" is almost 60,000 lines.

This ticket combined with #285598 is a menace for long chats. I've asked again and again across tickets, and no GitHub Copilot team member has ever confirmed that they have tested their product with a long-running chat with a size in this range.

```
Version: 1.131.0 (user setup)
Commit: e4c7e7b1d6d060162f4aa7f8225271b67ce1df75
Date: 2026-07-28T10:51:25Z
Electron: 42.7.0
ElectronBuildId: 14710161
Chromium: 148.0.7778.280
Node.js: 24.18.0
V8: 14.8.178.38-electron.0
OS: Windows_NT x64 10.0.26200
```