A freshly installed Cursor opens a Python repository and offers no completion, no go-to-definition and no type checking. What has to happen before those features work?

The principle — Cursor ships an editor, not a per-language toolchain. Completion, navigation and type checking for a given language arrive with an extension installed for that language.

Why the key is correct — The migration guidance is explicit that language support comes from extensions rather than built-in plugins, so a Python or Go repository stays silent until the matching extension is installed.

Why the others are wrong — Reindexing rebuilds search context and cannot conjure a language server that was absent. No setup wizard provisions a toolchain, because folders are opened directly. And no bundled language plugin is queued to arrive later, so waiting changes nothing at all.

Remember this — A quiet editor in a new language means a missing extension far more often than a broken install.

Sources — Cursor's Migrate from JetBrains help page.