[BUG] Claude Code extension crashes inside Cursor (Extension Host loop-crashing) #11738

Preflight Checklist

• I have searched existing issues and this hasn't been reported yet
• This is a single bug report (please file separate reports for different bugs)
• I am using the latest version of Claude Code

What's Wrong?

Summary

The Claude Code for VS Code extension does not work inside Cursor.
When opening Claude Code and sending any request, it gets stuck on “Combobulating…” forever. At the same time, Cursor’s Extension Host crashes and restarts repeatedly, which makes the Claude extension unusable.

It looks like Claude Code triggers an Extension Host crash together with Cursor’s own extensions, causing a restart loop. The log shows multiple warnings, missing API proposals, a service worker mismatch, and repeated Extension Host termination with Code: 5.

⸻

Environment
• Editor: Cursor (VS Code fork)
• Plugin: Anthropic.claude-code (Claude Code for VS Code)
• Version: 2.0.42
• OS: macOS (Apple Silicon / M1)

⸻

Steps to Reproduce
1. Open Cursor.
2. Install Claude Code for VS Code extension.
3. Open the Claude Code side panel.
4. Type anything (e.g., “test”) and send.
5. Panel freezes on “Combobulating…”.
6. Extension Host crashes and restarts repeatedly in console.

⸻

Expected Behavior

Claude Code should process the request normally and return a response.

⸻

Actual Behavior
• Claude Code UI is stuck at “Combobulating…”.
• Extension Host keeps crashing with Code: 5 and restarting.
• Cursor becomes unstable after that point.

What Should Happen?

Expected Behavior

Claude Code should process the request normally and return a response.

Error Messages/Logs

workbench.desktop.main.js:1484 This document requires 'TrustedScript' assignment.
(anonymous) @ workbench.desktop.main.js:1484
workbench.desktop.main.js:1484 The JavaScript Function constructor does not accept TrustedString arguments. See https://github.com/w3c/webappsec-trusted-types/wiki/Trusted-Types-for-function-constructor for more information.
workbench.desktop.main.js:55  WARN Missing property "rpcFileLoggerFolder" in oldValue. Filling with value from initValue. Please add a migration if necessary.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55  WARN Via 'product.json#extensionEnabledApiProposals' extension 'ms-toolsai.datawrangler' wants API proposal 'debugFocus' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55  WARN Via 'product.json#extensionEnabledApiProposals' extension 'ms-vscode.vscode-copilot-data-analysis' wants API proposal 'chatVariableResolver' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55  WARN Via 'product.json#extensionEnabledApiProposals' extension 'ms-python.python' wants API proposal 'terminalShellType' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55  WARN Via 'product.json#extensionEnabledApiProposals' extension 'ms-python.vscode-python-envs' wants API proposal 'terminalShellType' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55  WARN Via 'product.json#extensionEnabledApiProposals' extension 'github.copilot-chat' wants API proposal 'chatReadonlyPromptReference' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55  WARN Via 'product.json#extensionEnabledApiProposals' extension 'ms-azuretools.vscode-azure-github-copilot' wants API proposal 'lmTools' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55  WARN Via 'product.json#extensionEnabledApiProposals' extension 'vscjava.vscode-java-pack' wants API proposal 'lmTools' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55  WARN Via 'product.json#extensionEnabledApiProposals' extension 'apidev.azure-api-center' wants API proposal 'chatParticipant' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55  WARN Via 'product.json#extensionEnabledApiProposals' extension 'apidev.azure-api-center' wants API proposal 'languageModels' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55   ERR [Extension Host] (node:15171) [DEP0040] DeprecationWarning: The `punycode` module is deprecated. Please use a userland alternative instead.
(Use `Cursor Helper (Plugin) --trace-deprecation ...` to show where the warning was created)
error @ workbench.desktop.main.js:55
workbench.desktop.main.js:4957 [Extension Host] (node:15171) [DEP0040] DeprecationWarning: The `punycode` module is deprecated. Please use a userland alternative instead.
(Use `Cursor Helper (Plugin) --trace-deprecation ...` to show where the warning was created)
L3h @ workbench.desktop.main.js:4957
workbench.desktop.main.js:7501 Failed to load team commands: ConnectError: [unauthenticated] Error
    at t (workbench.desktop.main.js:4989:400501)
    at async Object.getTeamCommands (workbench.desktop.main.js:590:71574)
    at async wvo.loadTeamCommands (workbench.desktop.main.js:7501:2992)
loadTeamCommands @ workbench.desktop.main.js:7501
An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing.
An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing.
An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing.
An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing.
An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing.
An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing.
workbench.desktop.main.js:7498 Extension Host
workbench.desktop.main.js:7494 Extension host (LocalProcess pid: 15171) terminated unexpectedly. Code: 5, Signal: unknown
_onExtensionHostCrashed @ workbench.desktop.main.js:7494
workbench.desktop.main.js:55   ERR Extension host (LocalProcess pid: 15171) terminated unexpectedly. The following extensions were running: vscode.emmet, anysphere.cursor-agent-exec, vscode.git-base, vscode.npm, vscode.git, vscode.github, anysphere.cursor-always-local, cursor.cursor-browser-automation, anysphere.cursor-browser-connect, anysphere.cursor-browser-extension, anysphere.cursor-deeplink, anysphere.cursor-mcp, anysphere.cursor-retrieval, anysphere.cursor-shadow-workspace, vscode.debug-auto-launch, vscode.merge-conflict, Anthropic.claude-code, vscode.github-authentication, vscode.configuration-editing, vscode.extension-editing, vscode.json-language-features
error @ workbench.desktop.main.js:55
workbench.desktop.main.js:55   ERR No registered selector for ID: ms-vscode.npm-command
error @ workbench.desktop.main.js:55
workbench.desktop.main.js:55   ERR [Extension Host] (node:15461) [DEP0040] DeprecationWarning: The `punycode` module is deprecated. Please use a userland alternative instead.
(Use `Cursor Helper (Plugin) --trace-deprecation ...` to show where the warning was created)
error @ workbench.desktop.main.js:55
workbench.desktop.main.js:4957 [Extension Host] (node:15461) [DEP0040] DeprecationWarning: The `punycode` module is deprecated. Please use a userland alternative instead.
(Use `Cursor Helper (Plugin) --trace-deprecation ...` to show where the warning was created)
L3h @ workbench.desktop.main.js:4957
index.html?id=fcc2704b-0726-4eaa-ad22-72040a3f38bc&origin=2c661ed7-af41-4383-abc9-a43ac8b8db93&swVersion=4&extensionId=Anthropic.claude-code&platform=electron&vscode-resource-base-authority=vscode-resource.vscode-cdn.net&parentOrigin=vscode-file%3A%2F%2Fvscode-app:281 Found unexpected service worker controller. Found: vscode-webview://125dr2j47uri36upjk8r1fi9sapfe94d7etqhtb3mlv79be4ci72/service-worker.js?v=4&vscode-resource-base-authority=vscode-resource.vscode-cdn.net&id=2643881c-db0f-4c24-a1eb-24f9e56440bc&remoteAuthority=. Expected: service-worker.js?v=4&vscode-resource-base-authority=vscode-resource.vscode-cdn.net&id=fcc2704b-0726-4eaa-ad22-72040a3f38bc&remoteAuthority=. Waiting for controllerchange.
workbench.desktop.main.js:7498 Extension Host
workbench.desktop.main.js:7494 Extension host (LocalProcess pid: 15461) terminated unexpectedly. Code: 5, Signal: unknown
_onExtensionHostCrashed @ workbench.desktop.main.js:7494
workbench.desktop.main.js:55   ERR Extension host (LocalProcess pid: 15461) terminated unexpectedly. The following extensions were running: vscode.emmet, anysphere.cursor-agent-exec, vscode.git-base, vscode.npm, vscode.git, vscode.github, anysphere.cursor-always-local, cursor.cursor-browser-automation, anysphere.cursor-browser-connect, anysphere.cursor-browser-extension, anysphere.cursor-deeplink, anysphere.cursor-mcp, anysphere.cursor-retrieval, anysphere.cursor-shadow-workspace, vscode.debug-auto-launch, vscode.merge-conflict, Anthropic.claude-code, vscode.github-authentication, vscode.configuration-editing, vscode.extension-editing, vscode.json-language-features
error @ workbench.desktop.main.js:55
workbench.desktop.main.js:55   ERR No registered selector for ID: ms-vscode.npm-command
error @ workbench.desktop.main.js:55
workbench.desktop.main.js:55   ERR [Extension Host] (node:15645) [DEP0040] DeprecationWarning: The `punycode` module is deprecated. Please use a userland alternative instead.
(Use `Cursor Helper (Plugin) --trace-deprecation ...` to show where the warning was created)
error @ workbench.desktop.main.js:55
workbench.desktop.main.js:4957 [Extension Host] (node:15645) [DEP0040] DeprecationWarning: The `punycode` module is deprecated. Please use a userland alternative instead.
(Use `Cursor Helper (Plugin) --trace-deprecation ...` to show where the warning was created)
L3h @ workbench.desktop.main.js:4957

Steps to Reproduce

Steps to Reproduce
1. Open Cursor.
2. Install Claude Code for VS Code extension.
3. Open the Claude Code side panel.
4. Type anything (e.g., “test”) and send.
5. Panel freezes on “Combobulating…”.
6. Extension Host crashes and restarts repeatedly in console.

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

No response

Claude Code Version

2.0.42

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Cursor

Additional Information

Console logs.

workbench.desktop.main.js:1484 This document requires 'TrustedScript' assignment.
(anonymous) @ workbench.desktop.main.js:1484
workbench.desktop.main.js:1484 The JavaScript Function constructor does not accept TrustedString arguments. See https://github.com/w3c/webappsec-trusted-types/wiki/Trusted-Types-for-function-constructor for more information.
workbench.desktop.main.js:55 WARN Missing property "rpcFileLoggerFolder" in oldValue. Filling with value from initValue. Please add a migration if necessary.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55 WARN Via 'product.json#extensionEnabledApiProposals' extension 'ms-toolsai.datawrangler' wants API proposal 'debugFocus' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55 WARN Via 'product.json#extensionEnabledApiProposals' extension 'ms-vscode.vscode-copilot-data-analysis' wants API proposal 'chatVariableResolver' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55 WARN Via 'product.json#extensionEnabledApiProposals' extension 'ms-python.python' wants API proposal 'terminalShellType' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55 WARN Via 'product.json#extensionEnabledApiProposals' extension 'ms-python.vscode-python-envs' wants API proposal 'terminalShellType' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55 WARN Via 'product.json#extensionEnabledApiProposals' extension 'github.copilot-chat' wants API proposal 'chatReadonlyPromptReference' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55 WARN Via 'product.json#extensionEnabledApiProposals' extension 'ms-azuretools.vscode-azure-github-copilot' wants API proposal 'lmTools' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55 WARN Via 'product.json#extensionEnabledApiProposals' extension 'vscjava.vscode-java-pack' wants API proposal 'lmTools' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55 WARN Via 'product.json#extensionEnabledApiProposals' extension 'apidev.azure-api-center' wants API proposal 'chatParticipant' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55 WARN Via 'product.json#extensionEnabledApiProposals' extension 'apidev.azure-api-center' wants API proposal 'languageModels' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
warn @ workbench.desktop.main.js:55
workbench.desktop.main.js:55 ERR [Extension Host] (node:15171) [DEP0040] DeprecationWarning: The punycode module is deprecated. Please use a userland alternative instead.
(Use Cursor Helper (Plugin) --trace-deprecation ... to show where the warning was created)
error @ workbench.desktop.main.js:55
workbench.desktop.main.js:4957 [Extension Host] (node:15171) [DEP0040] DeprecationWarning: The punycode module is deprecated. Please use a userland alternative instead.
(Use Cursor Helper (Plugin) --trace-deprecation ... to show where the warning was created)
L3h @ workbench.desktop.main.js:4957
workbench.desktop.main.js:7501 Failed to load team commands: ConnectError: [unauthenticated] Error
at t (workbench.desktop.main.js:4989:400501)
at async Object.getTeamCommands (workbench.desktop.main.js:590:71574)
at async wvo.loadTeamCommands (workbench.desktop.main.js:7501:2992)
loadTeamCommands @ workbench.desktop.main.js:7501
An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing.
An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing.
An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing.
An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing.
An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing.
An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can escape its sandboxing.
workbench.desktop.main.js:7498 Extension Host
workbench.desktop.main.js:7494 Extension host (LocalProcess pid: 15171) terminated unexpectedly. Code: 5, Signal: unknown
_onExtensionHostCrashed @ workbench.desktop.main.js:7494
workbench.desktop.main.js:55 ERR Extension host (LocalProcess pid: 15171) terminated unexpectedly. The following extensions were running: vscode.emmet, anysphere.cursor-agent-exec, vscode.git-base, vscode.npm, vscode.git, vscode.github, anysphere.cursor-always-local, cursor.cursor-browser-automation, anysphere.cursor-browser-connect, anysphere.cursor-browser-extension, anysphere.cursor-deeplink, anysphere.cursor-mcp, anysphere.cursor-retrieval, anysphere.cursor-shadow-workspace, vscode.debug-auto-launch, vscode.merge-conflict, Anthropic.claude-code, vscode.github-authentication, vscode.configuration-editing, vscode.extension-editing, vscode.json-language-features
error @ workbench.desktop.main.js:55
workbench.desktop.main.js:55 ERR No registered selector for ID: ms-vscode.npm-command
error @ workbench.desktop.main.js:55
workbench.desktop.main.js:55 ERR [Extension Host] (node:15461) [DEP0040] DeprecationWarning: The punycode module is deprecated. Please use a userland alternative instead.
(Use Cursor Helper (Plugin) --trace-deprecation ... to show where the warning was created)
error @ workbench.desktop.main.js:55
workbench.desktop.main.js:4957 [Extension Host] (node:15461) [DEP0040] DeprecationWarning: The punycode module is deprecated. Please use a userland alternative instead.
(Use Cursor Helper (Plugin) --trace-deprecation ... to show where the warning was created)
L3h @ workbench.desktop.main.js:4957
index.html?id=fcc2704b-0726-4eaa-ad22-72040a3f38bc&origin=2c661ed7-af41-4383-abc9-a43ac8b8db93&swVersion=4&extensionId=Anthropic.claude-code&platform=electron&vscode-resource-base-authority=vscode-resource.vscode-cdn.net&parentOrigin=vscode-file%3A%2F%2Fvscode-app:281 Found unexpected service worker controller. Found: vscode-webview://125dr2j47uri36upjk8r1fi9sapfe94d7etqhtb3mlv79be4ci72/service-worker.js?v=4&vscode-resource-base-authority=vscode-resource.vscode-cdn.net&id=2643881c-db0f-4c24-a1eb-24f9e56440bc&remoteAuthority=. Expected: service-worker.js?v=4&vscode-resource-base-authority=vscode-resource.vscode-cdn.net&id=fcc2704b-0726-4eaa-ad22-72040a3f38bc&remoteAuthority=. Waiting for controllerchange.
workbench.desktop.main.js:7498 Extension Host
workbench.desktop.main.js:7494 Extension host (LocalProcess pid: 15461) terminated unexpectedly. Code: 5, Signal: unknown
_onExtensionHostCrashed @ workbench.desktop.main.js:7494
workbench.desktop.main.js:55 ERR Extension host (LocalProcess pid: 15461) terminated unexpectedly. The following extensions were running: vscode.emmet, anysphere.cursor-agent-exec, vscode.git-base, vscode.npm, vscode.git, vscode.github, anysphere.cursor-always-local, cursor.cursor-browser-automation, anysphere.cursor-browser-connect, anysphere.cursor-browser-extension, anysphere.cursor-deeplink, anysphere.cursor-mcp, anysphere.cursor-retrieval, anysphere.cursor-shadow-workspace, vscode.debug-auto-launch, vscode.merge-conflict, Anthropic.claude-code, vscode.github-authentication, vscode.configuration-editing, vscode.extension-editing, vscode.json-language-features
error @ workbench.desktop.main.js:55
workbench.desktop.main.js:55 ERR No registered selector for ID: ms-vscode.npm-command
error @ workbench.desktop.main.js:55
workbench.desktop.main.js:55 ERR [Extension Host] (node:15645) [DEP0040] DeprecationWarning: The punycode module is deprecated. Please use a userland alternative instead.
(Use Cursor Helper (Plugin) --trace-deprecation ... to show where the warning was created)
error @ workbench.desktop.main.js:55
workbench.desktop.main.js:4957 [Extension Host] (node:15645) [DEP0040] DeprecationWarning: The punycode module is deprecated. Please use a userland alternative instead.
(Use Cursor Helper (Plugin) --trace-deprecation ... to show where the warning was created)
L3h @ workbench.desktop.main.js:4957