Clicking agent thinking trace freezes Cursor: “The window is not responding” (Glass / workbench.glass.main.js)

Support Bug Reports
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1

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

On macOS, clicking an Agent thinking / thought trace accordion frequently freezes the Cursor window. macOS then shows “The window is not responding” (Reopen / Close / Keep Waiting).

This reproduces often when expanding thinking traces after an agent turn.

Logs from the exact incident (screenshot timestamp ~09:54 local) show the renderer main thread blocked, then CodeWindow: detected unresponsive, with all unresponsive samples stuck in a recursive call stack inside workbench.glass.main.js (Kao repeatedly):

2026-08-09 09:53:55.988 [warning] [RendererPing] window 2 (pid 18112) blocked for ~15008ms
2026-08-09 09:54:01.315 [error] CodeWindow: detected unresponsive
2026-08-09 09:54:09.215 [error] CodeWindow unresponsive samples:
<1>
    at Kao (.../workbench.glass.main.js:379:23304)
    at Kao (.../workbench.glass.main.js:379:23497)
    at Kao (.../workbench.glass.main.js:379:23518)
    ... (same recursive Kao frames across all 7 samples)
Total Samples: 7

Steps to Reproduce

  1. Open Cursor IDE on macOS (Agents / Glass UI).
  2. Run an Agent chat that produces a thinking / thought process block (thinking model).
  3. After the thought finishes (or while reviewing the transcript), click the thinking / thought accordion to expand the trace.
  4. Observe the UI freeze; macOS presents ‚The window is not responding.

Expected Behavior

Expanding a thinking trace should open the thought content without freezing or making the window unresponsive.

Screenshots / Screen Recordings

download.png
download.png606×694 53.4 KB

Operating System

MacOS

Version Information

Version: 3.15.6
VSCode Version: 1.128.0
Commit: a1f686545fd0ce8917bbd2449f733551a9bce420
Date: 2026-08-06T01:41:03.876Z
Electron: 40.10.3
Chromium: 144.0.7559.236
OS: Darwin arm64 24.6.0
macOS: 15.7.4 (24G517)
Hardware: Apple M4 Max, 36 GB

For AI issues: which model did you use?

Occurs when reviewing agent thinking traces (not model-specific in my experience; happens when clicking the thought UI). Happy to attach a Request ID from a specific chat if useful.

For AI issues: add Request ID with privacy disabled

Not captured for this UI hang (freeze happens on click in the client, before/without a new network request). Can provide one from an affected chat on request.

Additional Information

~/Library/Application Support/Cursor/User/globalStorage/state.vscdb is currently ~2.0 GB (globalStorage total ~3.5 GB). Sharing in case storage bloat interacts with Glass thinking-trace expand/render.

  • User MCP servers configured (5): vercel, TalkToFigma, posthog, supabase, langfuse-docs (plus Cursor plugins).
  • After the unresponsive detection, extension hosts exited and [LocalAgentStorage] rescanned agent DBs (69 agent headers), consistent with a window recovery/reopen path.
  • Hang is correlated with expanding thinking UI in Glass (workbench.glass.main.js), not with a backend ‚ÄúPlanning next moves‚Äù stall.

Does this stop you from using Cursor

Yes - Cursor is unusable

7

Hey @Jakobi_Haskell ,
Expanding a thinking trace shouldn’t freeze the window like that. We’ve let the team know and this is an issue we’re tracking.

While we dig in: close any large or minified files open in the Agents window with word wrap on, and set Editor: Wrapping Strategy to simple in Settings (or "editor.wrappingStrategy": "simple" in settings.json). If VoiceOver or another accessibility tool is on, try with it off.

To help us reproduce, could you share:

  1. Your editor.wrappingStrategy and editor.accessibilitySupport values
  2. Which editor / diff / Output tabs were open when it froze
  3. Whether it still happens after a full quit (Cmd+Q) and reopen with only that chat open (no other file tabs)

I’ll post here when there’s an update.