The session's host has no browser, and no root. browser_rootfs.cr makes an Alpine root file system holding Chromium, and runs commands inside it, with bwrap in a user namespace. Its seed is bootstrap-qcow2's: Alpine 3.23.2's minirootfs, checked against Alpine's .sha256, etc/resolv.conf written from outside, then apk add from inside.

Needs: Crystal (1.19.1 here), bwrap, tar, unprivileged user namespaces, and about 760 MiB for the root file system. It is made at $HOME/browser-rootfs, outside the checkout, unless a path is given.

Make it (about a minute; run again, it changes nothing but adds what's missing):

crystal build tools/browser-rootfs/browser_rootfs.cr -o browser_rootfs
./browser_rootfs make

It ends by printing Chromium's version: Chromium 149.0.7827.53 Alpine Linux on 2026-11-04.

Open a page and print what its script drew:

./browser_rootfs run -- chromium-browser --headless --no-sandbox \
  --disable-gpu --disable-dev-shm-usage --virtual-time-budget=5000 \
  --dump-dom URL

--no-sandbox because Chromium's own sandbox can't nest in this one. It shares the host's network, so localhost is the host's. D-Bus errors on standard error are expected and harmless.