Headless vs headed browser testing — when do you run headed locally?

Most people run headed during development and headless in CI. But I'm curious about the exceptions: - When do you run headed in CI (is there ever a case)? - Do you run headed locally even for mature, non-debug test runs? - Has headless ever hidden a bug that was only reproducible in headed mode? Also: with Playwright's `--ui` mode being so useful, I'm starting to wonder if headless-first is still the right default for local development or if the tradeoff has shifted.