Hey!

> Wouldn't an agent in any capacity need a sandbox runtime to do agentic work?

Developers on Rivet use 3 different patterns:

- Just agents: many agents just need tools, such as customer support or personal agents

- Agents with lightweight sandbox: Rivet provides a V8 / WebAssembly sandboxing library for running JS & Python with a filesystem, which covers most workloads like data analysis, file processing, evals, and code mode (https://rivet.dev/agentos/)

- Agent outside of the sandbox: expose the sandbox to the agent as tools, which is better for blast radius, trust boundary, and orchestration (see below)

> Is the idea that state/memory/context and runtime env are separate concepts in rivet?

Exactly, Rivet Actors support running the harness outside of the sandbox. It's often referred to "separation of head from the hands."

I wrote a bit about why a while back: https://rivet.dev/blog/2026-07-27-run-your-harness-outside-t...

> When you say "sandboxes are too slow" do you mean needing to boot the sandbox to get back Agent state?

Specifically coldstarts. As LLMs are getting faster and have more realtime use cases, sandboxes are become the bottleneck on time to interactive for an agent.