Diagnose Vercel CLI setup problems with vercel doctor

Vercel's command-line tool now has a vercel doctor command that checks whether the CLI is set up correctly and prints the command that fixes each problem it finds. According to the changelog, it checks the installed CLI version, the login and current team, whether the folder is linked to a Vercel project, and the project configuration in vercel.json. It also reports active incidents from Vercel's status page, so a problem on Vercel's side appears in the same report as local setup problems. Each check reports OK, Warning, Failed or Skipped.

The command is built so a coding agent can run it as a first diagnostic step. Vercel says doctor works without a login or a linked project and never prompts, logs in or links a project by itself, so an agent can run it before guessing at a fix without it stopping for input or changing the login or project link. Adding --json returns each check's status and suggested commands as structured data the agent can read directly. Doctor reports and suggests; the changelog describes no mode in which it applies fixes itself.

One check addresses a specific confusion: when vercel upgrade cannot update the installed CLI, the install check shows where the running CLI comes from and how to reinstall it.