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deeplethe/forkd

Fork-style microVM sandboxes for AI agents: children fork copy-on-write from a warmed Firecracker parent, KVM-isolated, with live BRANCH of running VMs.

Open-source alternative to:E2B

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What is it?

forkd is a microVM sandbox runtime built on Firecracker for workloads where many short-lived AI agent sandboxes need the same warmed environment. A parent VM boots once, imports its runtime and dependencies, and is paused to a snapshot. Each child is a separate Firecracker process that maps the parent's memory image with MAP_PRIVATE, so children share resident memory copy-on-write and spawn in roughly 100 ms rather than cold-booting a kernel.

Each child keeps hardware isolation through KVM and gets its own network namespace and cgroup v2 memory limit. forkd also provides BRANCH, which pauses a running sandbox, snapshots its in-flight state, and resumes it, with a live mode that shortens the source pause window. Snapshots can be stacked into diff chains, packed into portable archives, and pulled from a hub.

The project exposes a daemon with a REST API, a CLI, Python and TypeScript SDKs, and an MCP server for clients such as Claude Desktop and Cursor. It requires an x86_64 Linux host with KVM.

Key features

  • 01Creates child microVMs from a warmed parent snapshot via copy-on-write memory sharing.
  • 02Runs each child in its own KVM-backed Firecracker process with a separate network namespace.
  • 03Supports BRANCH to snapshot and resume a live sandbox, including a live mode with a shorter pause.
  • 04Chains diff snapshots and packs or unpacks them as portable archives.
  • 05Offers REST API, CLI, Python and TypeScript SDKs, and an MCP server.
  • 06Exposes Prometheus metrics and an append-only JSON audit log.

Use cases

  • Running code interpreter sessions where each request gets a fresh sandbox with preloaded libraries.
  • Running hundreds of parallel repository checkouts or test rollouts for agent evaluation.
  • Providing per-user code execution on a self-hosted Linux host with KVM isolation.
  • Forking a running agent's sandbox state to try several alternative next steps.

Quick start

  1. 1

    Install forkd following the README install section

  2. 2

    Fork 3 sandboxes from a snapshot tag

    forkd fork --tag py-pandas -n 1

Things to know

  • Requires Linux with KVM; it is not a macOS or Windows runtime.
  • Live BRANCH needs Linux 5.7+, a vendored Firecracker fork, and userfaultfd enabled.
  • The project is at v0.x, so interfaces may change between releases.

In collections

Open-source AI agent frameworks & apps

Topics

#ai-agents#sandbox#microvm#firecracker#kvm#copy-on-write#snapshot#rust

FAQ

What is forkd?
Fork-style microVM sandboxes for AI agents: children fork copy-on-write from a warmed Firecracker parent, KVM-isolated, with live BRANCH of running VMs. forkd is a microVM sandbox runtime built on Firecracker for workloads where many short-lived AI agent sandboxes need the same warmed environment. A parent VM boots once, imports its runtime and dependencies, and is paused to a snapshot. Each child is a separate Firecracker process that maps the parent's memory image with MAP_PRIVATE, so children share resident memory copy-on-write and spawn in roughly 100 ms rather than cold-booting a kernel.
Is forkd free to use? What license does it have?
forkd is open source under the Apache-2.0 license. Check the license terms before using it in commercial products.
Is forkd still maintained?
Actively maintained. The last commit to forkd was on Oct 24, 2026.
What can I use forkd for?
Running code interpreter sessions where each request gets a fresh sandbox with preloaded libraries. Running hundreds of parallel repository checkouts or test rollouts for agent evaluation. Providing per-user code execution on a self-hosted Linux host with KVM isolation. Forking a running agent's sandbox state to try several alternative next steps.
How do I install forkd?
Install forkd following the README install section Fork 3 sandboxes from a snapshot tag: forkd fork --tag py-pandas -n 1
Where can I get forkd?
The source code and installation instructions are on GitHub: https://github.com/deeplethe/forkd

Summary generated by AI from the project's README. GitHub stats refresh daily.

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