More ways to connect MCP servers

When adding an MCP server, you can now authenticate with custom HTTP headers (e.g. a personal access token) or static OAuth (client ID, secret, and scopes).

Codex models

Codex models are now fetched from the ChatGPT catalog, so the list stays up to date.

Fixes & improvements

• More reliable OAuth connections and a clearer header add/edit dialog.

• Opening a chat in a new tab no longer flashes and keeps your column layout and scroll position.