I recently vibe-coded a browser UserScript to ensure certain keys are always passed through to my browser (and any other scripts I'm running). There's also an 'aggressive mode' activated by an assignable hotkey for poorly behaved sites that refuse to pass through any keys.

  // ==UserScript==
  // @name           Key Passthrough 2.0
  // @description    Ensure specific hotkeys reach userscripts on greedy sites. Ctrl+Shift+/ toggles aggressive mode for sites that swallow keys entirely.
  // @run-at         document-start
  // @include        *
  // @exclude        http://192.168.*
  // Always-enabled key codes: 27=Esc, 116=F5 (Refresh), 166=Browser_Back, 167=Browser_Fwd, 191=/
  // Other keycodes to consider: 8=BS, 9=Tab, 16/160/161=Shift, 17/162/163=Ctrl, 18=Alt, 37=LArrow, 39=RArrow, 46=Delete, 112=F1
  // ==/UserScript==

  (function () {
    'use strict';

    // Keys to passthrough in normal mode.
    // Esc, Ctrl, / (191) and Browser nav (166/167) are the core cases.
    // F1/F5 included if you have AHK remaps on those.
    // Esc included to prevent sites trapping it in overlays.
    const PASSTHROUGH_KEYS = new Set([27, 116, 166, 167, 191]);

    // Aggressive mode toggle hotkey: Ctrl+Shift+/
    const AGGRESSIVE_TOGGLE_CODE = 191;

    const REFIRE_FLAG = '_kp_refire';

    let aggressiveMode = sessionStorage.getItem('kp_aggressive') === '1';

    const logPrefix = '[KeyPassthrough]';

    const announce = (msg) => console.log(`${logPrefix} ${msg}`);

    if (aggressiveMode) announce('Aggressive mode ON (persisted from earlier in session)');

    // --- Normal mode ---
    // We're first in the capture chain at document-start.
    // For passthrough keys, do nothing — just let the event propagate naturally.
    // The site's listeners follow ours in the chain, so we've already won the race.

    // --- Aggressive mode ---
    // For sites that still swallow keys via stopImmediatePropagation in an
    // inline <script> that races document-start: block the site's listeners,
    // then re-dispatch a clone after the current call stack clears so our
    // userscripts get a clean second shot.

    function refire(e) {
        // Build a plain init object from the original event
        const init = {
            key:            e.key,
            code:           e.code,
            keyCode:        e.keyCode,
            which:          e.which,
            charCode:       e.charCode,
            ctrlKey:        e.ctrlKey,
            shiftKey:       e.shiftKey,
            altKey:         e.altKey,
            metaKey:        e.metaKey,
            repeat:         e.repeat,
            bubbles:        true,
            cancelable:     true,
            composed:       true,
        };
        const clone = new KeyboardEvent(e.type, init);
        clone[REFIRE_FLAG] = true;
        // After current capture/bubble cycle fully completes
        setTimeout(() => document.dispatchEvent(clone), 0);
    }

    function handleKey(e) {
        // Ignore our own re-dispatched events
        if (e[REFIRE_FLAG]) return;

        // Aggressive mode toggle: Ctrl+Shift+/
        if (e.ctrlKey && e.shiftKey && e.keyCode === AGGRESSIVE_TOGGLE_CODE) {
            aggressiveMode = !aggressiveMode;
            sessionStorage.setItem('kp_aggressive', aggressiveMode ? '1' : '0');
            announce(`Aggressive mode ${aggressiveMode ? 'ON' : 'OFF'}`);
            e.stopImmediatePropagation();
            return;
        }

        if (!PASSTHROUGH_KEYS.has(e.keyCode)) return;

        if (aggressiveMode) {
            // Block the site from seeing this key, then re-dispatch for our scripts
            e.stopImmediatePropagation();
            refire(e);
        }
        // Normal mode: do nothing, let event propagate naturally
    }
    document.addEventListener('keydown', handleKey, true);
    document.addEventListener('keyup',   handleKey, true);
  })();