Claude Code tabs cause Cursor to freeze on startup (stuck loading)

Support Bug Reports
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1

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

When reopening Cursor with a previous session that includes Claude Code tabs (even just one), the entire UI gets stuck in a loading state.

The editor does not load properly
Claude tabs show “Waiting for extension host” indefinitely
No interaction is possible

This happens consistently after restarting Cursor or the system if Claude Code tabs were open in the previous session.

Steps to Reproduce:

Open Cursor
Open one or multiple Claude Code tabs
Restart Cursor or your computer
Reopen Cursor
Observe that everything is stuck loading

Expected Behavior:
Cursor should restore the previous session and load all tabs normally.

Actual Behavior:
Cursor freezes and remains stuck in a loading state until intervention.

Workarounds:

Close all Claude Code tabs before restarting Cursor (not practical)
Alternative workaround:
Open a new tab
Type something (e.g., “hello”)
Wait a few minutes until it times out
Cursor prompts to reload the app
After reload, everything works again

Impact:
High.
This breaks workflow completely because:

I rely on keeping multiple Claude Code tabs configured with specific agents
After every restart/update, I’m forced to rebuild my entire setup from scratch

Additional Notes:
This seems specifically tied to Claude Code tabs during session restore. Likely an issue with extension host initialization or session hydration.

Steps to Reproduce

see above

Operating System

MacOS

Version Information

Version: 2.7.0-pre.119.patch.0
VSCode Version: 1.105.1
Commit: f947fde72906f7ead2baf0a913c587bbb5bf3b80
Date: 2026-03-23T05:49:10.648Z
Build Type: Stable
Release Track: Nightly
Electron: 39.8.1
Chromium: 142.0.7444.265
Node.js: 22.22.1
OS: macOS (Darwin arm64 25.3.0)

Does this stop you from using Cursor

Yes - Cursor is unusable

1 Like
3

Hey, thanks for the detailed report. The repro steps and workaround are super helpful.

This looks related to a known issue where the extension host init times out on startup. A few things to help narrow it down:

  1. Can you open Developer Tools via Help > Toggle Developer Tools, go to the Console tab, and copy any red errors that show up while Cursor is stuck loading? That should tell us what’s hanging.

  2. Also check if the cursor-socket extension is intact. Run this in your terminal:

ls -la "/Applications/Cursor.app/Contents/Resources/app/extensions/cursor-socket/"

If you only see package.json and there’s no out/ directory, that’s a known packaging issue.

  1. Does cursor --disable-extensions let Cursor start normally? That would confirm whether it’s a Claude Code extension issue or a broader extension host problem.

The team knows about extension host timeout issues and is actively investigating. Your report is a useful data point, especially session restore with extension tabs as a trigger.

Share the console logs when you can. That’ll help confirm if this is the same root cause or something specific to Claude Code session restore.

4

Ran cursor --disable-extensions — same issue, extensions aren’t the cause. Also checked the cursor-socket extension directory and it has dist/, extension.webpack.config.js, and package.json all present, so it’s not the packaging issue either.

Console logs attached below. The key errors I’m seeing:

  • Extension host v3 health check failed after 10 attempts (7051ms)

  • [auth] Timeout waiting for auth ready signal repeating dozens of times

  • [PluginsProviderService] Timed out waiting for plugins provider after 30000ms

  • [Anthropic.claude-code]: View container ‘claude-sidebar-secondary’ does not exist

  • 429 rate limit from api2.cursor.sh at the very bottom

Looks like the auth/backend connection is what’s hanging, not extensions. The 429 rate limit from Cursor’s API might be triggering the whole cascade.

image
image2532×2778 1.64 MB

5

Hey why this isn’t resolved yet? The issue is still here even with version…

Version: 2.7.0-pre.151.patch.0
VSCode Version: 1.105.1
Commit: 138452aa54d8d7f0b30ccf08b9280d72abd726e0
Date: 2026-03-27T16:45:39.103Z
Layout: editor
Build Type: Stable
Release Track: Nightly
Electron: 39.8.1
Chromium: 142.0.7444.265
Node.js: 22.22.1
V8: 14.2.231.22-electron.0
OS: Darwin arm64 25.4.0

6

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

Here’s everything ready to paste:

Describe the Bug:

Cursor IDE becomes completely unresponsive when restoring Claude Code extension (anthropic.claude-code) webview tabs on startup. Terminal stops working, extensions fail to load, and settings cannot be opened. The IDE appears fully broken/corrupted but the actual cause is Cursor’s webview deserialization hanging the renderer process.

The same extension with the same sessions works perfectly in VS Code — this is a Cursor-specific bug in the webview panel restore path.

Steps to Reproduce

Install Claude Code extension (anthropic.claude-code) in Cursor
Open any project folder
Open a Claude Code session as an editor tab (not sidebar)
Close Cursor with the Claude Code tab still open
Reopen Cursor — it will attempt to restore the Claude Code tab
Terminal, extensions, and settings all stop working. Extension hosts start then exit gracefully after ~30 seconds.
Even a single Claude Code tab with a 187KB session triggers the hang. The number of tabs or session size does not matter.

Expected Behavior

Cursor should restore Claude Code webview tabs without hanging the renderer, just like VS Code does with the identical extension and data.

Operating System

Windows 10/11

Version Information

IDE:
Version: 3.0.12
VSCode Version: 1.105.1
Commit: a80ff7dfcaa45d7750f6e30be457261379c29b00

For AI issues: which model did you use?

Non model specific

Additional Information

Technical root cause analysis:

The bug is in Cursor’s registerWebviewPanelSerializer restore path for claudeVSCodePanel panels. The hang occurs before the extension’s deserializeWebviewPanel handler executes — even patching the handler to immediately call panel.dispose() does not prevent the hang.

Logs show extension hosts start normally then all exit with code 0 after ~30 seconds. Renderer log shows No Connect transport provider registered errors, indicating the shared process IPC breaks due to the renderer being blocked.

Workaround: Remove claudeVSCodePanel entries from memento/workbench.parts.editor in each workspace’s state.vscdb (located in %APPDATA%/Cursor/User/workspaceStorage//state.vscdb). Session history in ~/.claude/projects/ is unaffected — only the auto-restore tabs cause the issue.

Confirmed NOT caused by: cache corruption, bloated state.vscdb, extension conflicts, session data size, or number of open tabs. Isolated through systematic testing.

Does this stop you from using Cursor

Yes - Cursor is unusable

10

Same issue, infinite loading of the extension on startup