What are Sailboxes and why should I use them?
Sailboxes are persistent Linux VMs designed for long-horizon agents. They can be dynamically provisioned in seconds and are the perfect cloud environment for any agent. They provide a number of advantages over other sandboxing providers:- Cost efficiency: not only is our pricing >70% less than other providers, Sailboxes only charge you for the exact portion of CPU, memory, and disk you use. Since agents spend most of their time blocked on I/O, we are significantly more cost-efficient than anyone else.
- Elastic scaling: use as much (or as little) compute as you need, up to your Sailbox size’s CPU, memory, and disk ceilings. Because billing follows actual usage, a higher ceiling costs nothing on its own.
- Pause, resume, and fork all sandbox state. In-flight work survives the pause with no save/restore code on your side, and open network connections survive for up to 10 minutes.
- Automatically sleep Sailboxes while waiting on Sail inference calls.
Provider comparison
*Modal allows bursting beyond reserved capacity, but this is best-effort (e.g. sandboxes OOM if no memory is available).
What is the tradeoff?
Sailboxes achieve their efficiency through live migrations: we are able to achieve much higher utilization on our underlying hardware than other providers by migrating VMs based on their live resource usage. These migrations only occur a few times a day, take several seconds, and happen completely without the knowledge of the agent. While these migrations mean that the occasional command incurs a few seconds of additional latency, the tradeoff is massive gains in cost-efficiency. Unlike human-in-the-loop workflows like chatbots where patience is limited, long-horizon agents can tolerate the occasional latency blip without issue. Sailboxes directly trade off this p99 latency for better economics and we believe this makes them the ideal platform for any long-horizon agent.Start here
- Quickstart: create a Sailbox, run commands, expose a service, and clean up.
- Pricing: understand observed-usage billing dimensions and per-hour rates.
- Images: choose a base image and build custom images with packages, commands, environment variables, and local files.
- Networking: expose HTTP services, raw TCP ports, and SSH from a Sailbox.
- Filesystem: read and write files at runtime, stream large files, and decide what belongs in an image.
- Lifecycle: checkpoint, start from checkpoint, pause, sleep, resume, upgrade, and terminate Sailboxes.
- HTTP API: create and operate Sailboxes over plain HTTP from any language.