+*******
+ Login
+*******
+
+The ``chatgpt`` endpoint needs a login with a ChatGPT account:
+
+.. code:: console
+
+ onechat login
+
+The command shows a link and a code. Open the link on any device, enter
+the code, and approve the login. Device code login must be allowed in
+the ChatGPT security settings. OneChat writes the tokens to
+``auth.json`` in the data directory, with mode 0600, and refreshes them
+before they expire. The file belongs to OneChat only. Do not share it
+with the Codex CLI, because each program rotates the refresh token and
+logs the other out.
+