[webpolis]

The hard part here isn't checkpointing the agent's conversation state — that's just a list. It's checkpointing the world state. If step 5 wrote rows to Postgres and step 7 called a third-party API, forking from step 6 means you need the DB at its post-step-5 snapshot and some way to mock or replay the external call. Without that, you're replaying agent logic against a world that's already diverged. We ran into this enough building agent sandboxing at Cyqle (https://cyqle.in) — our approach is snapshotting the entire ephemeral environment at each checkpoint so the fork includes filesystem, DB state, everything. Curious how Time Machine handles external side effects that can't be rolled back.