Caveats

The SSM fallback tunnel is about 1 MB/s. Repos that can’t come from GitHub push their history through it (a 300 MB history takes about 5 minutes, once per create). The create output says which transfer mode you got and why.
Parking stops processes. Files, git state, and installed tools survive, and on wake your tmux layout comes back (windows, panes, cwds, scrollback, claude/codex relaunched on their conversations) along with the Docker containers that were running. Processes outside Docker don’t survive: an agent mid-turn stops at its last saved message, and a dev server started in a pane comes back as its command typed at the prompt, one Enter away.
OAuth MCPs log in once per session, from inside it while attached. Keychain-held tokens can’t be copied safely.
ssh-key-only GitHub auth pushes while attached. The forwarded agent disconnects with you. Any token lifts this.
pier proxy is macOS-only for now. pier port works everywhere.
GCP wakes slower than AWS. Resume to attached is about a minute against EC2’s ~20s, and a running resize takes about two minutes. GCE stop/start simply takes longer.
A bake hook requires an image. A repo with a .pier/bake.sh gets no sessions until it’s baked: pier <branch> refuses rather than launching the stock image, where .pier/setup.sh would fail on missing toolchains.
Resize stays within the CPU arch (t4g to t4g). Providers only allow type changes on stopped instances.

Roadmap