Agent Stream Start Failed – Unable to start agent session

Support Bug Reports
, ,
3

Hey, it looks like this is an issue where the extension host hangs while initializing the agent, which causes ERROR_EXTENSION_HOST_TIMEOUT / deadline_exceeded. The team is aware and tracking it.

Here are a few things you can try:

  1. Disable MCP servers
    If you have them set up, turn them all off in Cursor Settings > Tools & MCP, then restart Cursor. MCP servers can cause the extension host to hang during init.

  2. Start without extensions
    Run this in Terminal:

    /Applications/Cursor.app/Contents/MacOS/Cursor --disable-extensions

    If this helps, re-enable extensions one by one to find the problematic one.

  3. Clear the databases (back up first):

    • Fully quit Cursor
    • Delete or rename the global DB: ~/Library/Application Support/Cursor/User/globalStorage/state.vscdb
    • You can also clear workspace data: ~/Library/Application Support/Cursor/User/workspaceStorage/{workspace hash}
    • Restart Cursor (you’ll need to sign in again)

  4. If nothing helps
    Try rolling back to a previous version: Download · Cursor.

Related reports and fixes:

Let me know what worked and what didn’t.