You aren’t at Shopify, and you can’t tag River in our Slack. But the point is not the agent on the surface. It’s the substrate underneath, and the core bet that produced it: the session is the thing that must survive.

If you’re building agent infrastructure, here are three priorities:

Decouple the brain from the hands. The harness does not live in the sandbox. When you commit to that boundary, safety, replaceability, and observability stop being trade-offs. You will not be able to retrofit it. Make the agent multiplayer by construction. A private agent has a ceiling: the person at the keyboard. A public agent teaches every session that comes after it. The corpus is the compounding asset; the privacy of an agent thread is a disadvantage. Treat the next agent as a profile, not a platform. The cost of a new agent product should be a new bundle on the same substrate. If your second agent forces a second platform, you haven’t built the substrate yet.

The session.