A server you added and used all last week is missing when you start Claude Code in a second repository on the same laptop. Nothing was uninstalled and your credentials are unchanged. Where should you look first?

The principle — A server that is absent and a server that is broken produce different symptoms, and the first question is always which of the two you are looking at.

Why the key is correct — Local-scoped servers are tied to the project where you added them: the repository root, or the exact directory if you were not in a git repository. Local scope is also the default, so any server added without a scope flag behaves this way. Opening a different repository puts you outside the only project the entry was ever filed under.

Why the others are wrong — Corruption would break the server in its original project as well, and there it still works. Availability across the whole machine is user scope's behaviour rather than the default. And an authentication problem leaves the server listed with a status attached to it, instead of removing it from the list.

Remember this — A server missing in one directory and present in another is a scope question before it is anything else.

Sources — Anthropic's Claude Code MCP quickstart.