Whether a page console message prints without --debug. Warnings and errors do, so CI logs capture browser-side failures; other levels are debug-only. Firefox also reports its own parser diagnostics as warnings — [JavaScript Warning: "unreachable code after return statement" …], about the bundle rather than anything the page said, and on every run — so those are debug-only.

import { showsWithoutDebug } from './browser.ts';

showsWithoutDebug('warning', 'deprecated option'); // true
showsWithoutDebug('log', 'hello'); // false
showsWithoutDebug('warning', '[JavaScript Warning: "unreachable code after return statement"]'); // false