Overview

What Fuse is and how its pieces fit together

Fuse is a control plane for agents: it deploys Firecracker microVMs onto your own hosts and drives their full lifecycle — provision, running, drain, destroy — through a REST API. It’s the orchestration layer sandboxed compute needs: scheduling across hosts, snapshots, host management, and live event streams, built on Firecracker and entirely open source.

The hard part of Firecracker has always been getting it running: host setup, the in-guest agent, building a rootfs. Fuse collapses all of that into a single script — one command brings up a host with the agent installed and a rootfs baked and ready.

What you get

• One-script Firecracker setup — host, agent, and a baked rootfs, ready to boot.
• Scheduling across hosts — register hosts, and Fuse places microVMs for you.
• Optional GPU environments — whole GPUs or fractional MIG instances, routed to QEMU/VFIO hosts.
• Full VM lifecycle — provision, running, drain, destroy, tracked and reconciled.
• Snapshots — capture a running microVM and restore from it.
• Live event streams — tail a microVM’s events over SSE.
• Durable state — backed by Postgres, or in-memory for local runs.
• Per-VM secrets — credentials generated per microVM, tokens encrypted at rest, when TOKEN_ENCRYPTION_KEY is set. Without it the orchestrator skips credential generation entirely (insecure mode).
• REST API and Prometheus metrics — drive everything over HTTP, observe it out of the box.

How the pieces fit together

• The orchestrator is the control plane: one HTTP API, a scheduler, and the source of truth for every environment, host, and snapshot.
• A host is a machine running a host agent (fc-agent for Firecracker, or qemu-agent for GPU hosts). You register hosts with the orchestrator; it schedules microVMs onto them.
• An environment is one microVM and the task running inside it. You describe what you want with a Fusefile or a raw resource spec, and the orchestrator picks a host, boots the VM, and tracks it through its lifecycle.
• A snapshot captures a running microVM so you can restore it later.

Read Concepts for the full mental model, or jump straight to the Quickstart to get a microVM running.

Where to go next