Fly.io's Sprite gives each agent a hardware-isolated Linux machine with 100GB persistent ext4 storage, no runtime caps, supervised long-running services, and a public HTTPS URL with automatic TLS.

The post benchmarks this against E2B, Blaxel, Vercel, Daytona, Modal, and Cloudflare on four criteria: file retention, process survival, network addressability, and credential injection without exposing API keys to the agent. Fly.io diverges from competitors' freeze-and-restore models by using supervised services, S3-backed block storage with unlimited checkpoints, and an external proxy for in-transit credential injection.