Claude Code includes a built-in diagnostic tool called doctor. You can run it from the command line with claude doctor.

This checks your installation and configuration for any issues. It's helpful if you run into problems later.

You can also run the /doctor command from within a Claude Code session to get the same diagnostic information.

One quick note: as of late January 2026, there's a bug where claude doctor doesn't exit properly when it finishes. If it seems stuck, just close the terminal window and open a new one.