Resuse headless puppeteer instance from PHP

I have a PHP app that needs to take some screenshots. Currently it spawns then destroys a Puppeteer/Chrome instance each time, but I want to re-use the instance to increase performance when it runs batches.

In pseudo code: script 1: launch Puppeteer, grab the instance URL/websocket address, disconnect; script2: loop over screenshots; script 3: close

My JS is letting me down I think – when it hits browser.disconnect(); it never returns to PHP as the process doesn’t complete.

—
Example code:

PHP: function spawn_chrome() { exec( 'node spawn_chrome.js', $command_output, $command_result ); [...] };

JS (spawn_chrome.js):

const puppeteer = require('/usr/local/lib/nodejs/node_modules/puppeteer');

(async () => {
  const browser = await puppeteer.launch({
    headless: 'shell',
    executablePath: '/usr/bin/chromium',
    args: [
      '--no-sandbox',
      [...]
      '--use-mock-keychain',
    ]
  });

  var browserWSEndpoint = browser.wsEndpoint();
  await browser.disconnect();

  console.log(browserWSEndpoint);
})();

If I replace await browser.disconnect(); with await browser.close(); the script finishes/returns. But according to the docs they both return a promise so I’m surprised they’re behaving differently.

Is my JS failing here? Or have I misunderstood it more fundamentally and you can’t disconnect and finish script processing while leaving the Chrome instance up?