Agent Sandboxing

4 open source tools compared. Sorted by stars — scroll down for our analysis.

Tool	Stars	Velocity	Language	License	Score
zeroboot Sub-millisecond VM sandboxes for AI agents via copy-on-write forking	1.9k	+1455/wk	Rust	Apache License 2.0	71
boxlite Sandboxes for every agent — embeddable, stateful, with snapshots and hardware isolation.	1.7k	+84/wk	Rust	Apache License 2.0	64
nono Kernel-enforced agent sandbox and security CLI/SDKs with capability-based isolation.	1.2k	+119/wk	Rust	Apache License 2.0	64
fence Lightweight, container-free sandbox for running commands with network and filesystem restrictions.	580	+11/wk	Go	Apache License 2.0	60

Our Analysis

zeroboot1.9k★

Zeroboot spawns VM sandboxes in 0.8 milliseconds — 190x faster than E2B. It pre-boots a Firecracker microVM, snapshots memory and CPU state, then forks new KVM VMs with copy-on-write memory. Each sandbox is a real VM with hardware-enforced isolation, not a container pretending to be one. This is infrastructure for running thousands of short-lived AI agent tasks. The ~265KB memory overhead per sandbox is absurdly efficient. Compared to E2B (cloud-based, slower), Zeroboot is self-hosted and faster. Compared to nono (kernel-level process isolation), Zeroboot provides full VM isolation. Compared to Docker (container-level), you get real hardware boundaries. Use this when you need to spin up disposable execution environments for AI agents at massive scale. Skip this unless you're running infrastructure — this is a platform primitive, not an end-user tool. The catch: Linux-only (requires KVM), so no macOS development. The managed API is early access, and self-hosting Firecracker requires real ops knowledge. Apache 2.0 license is clean.

boxlite1.7k★

Boxlite gives AI agents their own sandboxed VMs with actual hardware isolation — not containers, not namespaces, but real separate kernels. Each "Box" is persistent, stateful, and snapshot-able, so your agent can install packages, modify files, and pick up where it left off. Run it locally first, scale out when ready. If you're building AI agents that execute code and need isolation stronger than Docker, Boxlite is the self-hosted option. E2B is the market leader with Firecracker microVMs and half the Fortune 500 as customers. Modal handles GPU workloads and serverless compute that Boxlite doesn't touch. Daytona offers development environments as a service. The catch: Boxlite is nascent — 1,600 stars, early-stage project. E2B has years of production hardening and a massive SDK ecosystem. Boxlite's persistence model is a differentiator but also means you're managing stateful VMs, not ephemeral sandboxes. The project runs on your infrastructure, so you own the scaling, security, and maintenance. For production agent workloads, E2B is the safer bet today.

nono1.2k★

nono is kernel-enforced sandboxing for AI agents — not policy-based filtering, but OS-level restrictions using Landlock (Linux) and Seatbelt (macOS) that are structurally impossible to bypass once applied. It wraps your agent in an irreversible capability sandbox with API key protection, destructive action guardrails, and full snapshot/rollback. This is real security, not theater. Unlike Docker (container-level, escapable), nono applies restrictions directly to the process with zero infrastructure overhead. Compared to Zeroboot (VM-level, Linux-only), nono is lighter and cross-platform. Compared to Fence (CLI wrapper, simpler), nono goes deeper with cryptographic audit chains and atomic rollback. Use this when you're running AI agents on machines with real data and want genuine isolation. Skip this if you only run agents in disposable cloud environments. The catch: the sandbox is irreversible by design — if your policy is too restrictive, you restart the process. Built-in agent profiles help, but custom policies require understanding OS security primitives. Apache 2.0 license, actively maintained.

fence580★

Fence wraps any command in a sandbox that blocks network access by default and restricts filesystem operations — no containers, no VMs, just a Go binary. Run fence npm install and it only allows npm/PyPI traffic. Run fence rm -rf / and it blocks the command entirely. The simplicity is the point. Pre-built templates for common workflows (code, build, test), configurable deny rules, and it works with every major coding agent — Claude Code, Codex, Gemini CLI, Cursor. Compared to nono (deeper, kernel-enforced), Fence is easier to adopt. Compared to Docker (heavier, container overhead), Fence is lighter. Compared to running commands raw, Fence adds real protection. Use this when you're running semi-trusted code — package installs, build scripts, unfamiliar repos — and want basic guardrails without infrastructure. Skip this if you need full VM isolation or audit trails. The catch: nascent at 578 stars. Filesystem restrictions are configurable but the defaults may surprise you — test your workflow before depending on it. Go binary means no runtime dependencies, which is nice. Apache 2.0 license.