Error messages

Waiting for extension host

Waiting for extension host

You send a message and the chat sits on this instead of answering:

Waiting for extension host

After a while it usually gives up with an error. Here's the full JSON a Windows user pasted on September 18, 2026, on Cursor 3.21.9:

{"error":"ERROR_EXTENSION_HOST_TIMEOUT","details":{"title":"Agent Execution Timed Out","detail":"The agent execution provider did not respond in time. This may indicate the extension host is not running or is unresponsive.","isRetryable":false,"shouldShowImmediateError":true,"additionalInfo":{},"buttons":[{"label":"Reload Window","reloadWindow":{}}],"planChoices":[]}}

In January 2026, on 2.4.14, the same failure said the provider "did not respond within 16 seconds". When we read the forum on September 26, 2026, the main thread from then had 18,793 views and a March thread about 2.6 had 5,932. We counted 46 more topics with "Agent execution timed out" in the title.

What the extension host is

The extension host is a separate background process, inherited from VS Code, that runs your extensions. It isn't only for extensions in Cursor, though: the agent's local side (the part that reads files and runs commands) runs through it too, and that's why a stuck extension host stops chat dead. A Cursor staffer put it plainly in August 2026: "the part of Cursor that runs agent commands didn't start up in time, so the request never reached our servers." So it's rarely your network or your account.

Cursor's support engineer said in March that "Waiting for Extension Host" "can be a symptom of many different issues". We went through the 2026 threads for the ones they've actually pinned down.

Causes Cursor staff have confirmed

The big one this month is a setting. A recent change didn't handle "Index Repositories for Instant Grep" being turned off, so every request waited and then timed out. Reinstalling won't help: the switch lives in your settings, and those survive a reinstall. Turn it on under Cursor Settings (it's on the Indexing tab, which some layouts call Code Intelligence) and accept the reload. Staff said on September 22 that 3.21.18 fixes it, so if you're on that build or later it shouldn't be this.

On macOS 27, an old Intel-only git first on your PATH hangs the agent if Rosetta didn't come across with the upgrade. Staff said on September 25 that a fix has landed for a coming version. Until then, move that git out of /usr/local/bin or run softwareupdate --install-rosetta --agree-to-license.

Windows has its own. We found two that staff traced. On one managed machine the agent's runner couldn't start at all because PowerShell was blocked, and setting Git Bash as the default terminal got around it. On another, security software was holding files under .cursor at startup; staff suggested excluding %LOCALAPPDATA%\Programs\cursor\, %ProgramFiles%\cursor\ and %APPDATA%\Cursor.

Then there've been plain bad builds, which you can't do much about. 2.6.14 shipped missing a folder in its cursor-socket extension, fixed in 2.6.18 three days after the reports started. The long 2.4 stretch of this error was "addressed", staff wrote in April, with more fixes through 3.0. (Our favorite: an environment variable whose name was just digits stopped the extension host from starting. That one's fixed in 3.20, and we'd never have guessed it.)

What to try, in order

• Update Cursor, then quit it completely (on Windows, end any Cursor processes left in Task Manager) and reopen. Several of the causes above are fixed in current builds.
• Run Developer: Restart Extension Host from the Command Palette.
• Start with cursor --disable-extensions. If the agent works that way, it's an extension, and you'll find it by turning them back on a few at a time. Then try cursor --profile-temp, which staff suggested to rule out your settings.
• Check the size of state.vscdb in %APPDATA%\Cursor\User\globalStorage\ (Windows) or ~/Library/Application Support/Cursor/User/globalStorage/ (macOS). Staff said in April that if it's "over 1-2 GB, renaming it and restarting Cursor can help", though you'll have to sign in again.

If none of that's worked, staff want the red errors from Help, Toggle Developer Tools, Console, or the output of Developer: Capture and Send Debugging Data, posted with your version in a new forum thread. They also ask whether you're working locally or over Remote SSH or WSL, since the extension host runs on the remote machine in those setups and fails in its own ways there.