Bind M-[ and M-] when not in a terminal

Question

What is the correct way to bind keys only for X frames? E.g. some key combinations are part of terminal escape sequences, but otherwise should be bindable when not running in a terminal.

Currently, I use an after-make-frame-functions hook:

(defun my-setup-nontty-bindings (frame)
  "Set up TTY-incompatible keybinds for FRAME, if it's not a TTY."
    (unless overriding-terminal-local-map
      (setq overriding-terminal-local-map (make-sparse-keymap)))
    (define-key overriding-terminal-local-map (kbd "M-[") 'cs/forward-or-backward-sexp)
    (define-key overriding-terminal-local-map (kbd "M-]") 'er/expand-region)))
(add-hook 'after-make-frame-functions 'my-setup-nontty-bindings)

This almost works, however:

• A frame is not exactly the same as a terminal, and overriding-terminal-local-map is a per-terminal, not per-frame variable;
• A non-nil overriding-terminal-local-map breaks international input, which is apparently by design.