How OpenAI’s Open‑Source Tart Enables macOS and Linux VMs on Apple Silicon

Overview

Tart is an open‑source virtualization toolset hosted on GitHub that runs macOS and Linux virtual machines on Apple Silicon (M1/M2/M3/M4) using Apple’s Virtualization.Framework . It provides Docker‑style image management, OCI‑compatible push/pull, a Packer plugin for automated VM creation, and native integration with CI systems.

Key capabilities

Near‑native performance by leveraging Virtualization.Framework.

VM images can be pushed to or pulled from any OCI‑compatible registry (e.g., ghcr.io, Docker Hub).

Packer plugin automates VM build pipelines.

CLI commands mirror Docker workflow: tart clone, tart run, tart push.

Installation

Three commands install Tart via Homebrew, clone a macOS Tahoe base image, and start the VM:

brew install cirruslabs/cli/tart

tart clone ghcr.io/cirruslabs/macos-tahoe-base:latest tahoe-base

tart run tahoe-base

The base image is ~25 GB. Manual installation is also possible:

curl -LO https://github.com/cirruslabs/tart/releases/latest/download/tart.tar.gz

tar -xzvf tart.tar.gz

./tart.app/Contents/MacOS/tart clone ghcr.io/cirruslabs/macos-tahoe-base:latest tahoe-base

./tart.app/Contents/MacOS/tart run tahoe-base

System requirements: Apple Silicon with macOS 13.0 (Ventura) or later.

Core operations

SSH into a VM : ssh admin@$(tart ip tahoe-base) Directory mounting (host → VM): tart run --dir=project:~/src/project vm macOS guests auto‑mount to /Volumes/My Shared Files/project; Linux guests require manual mount:

sudo mkdir /mnt/shared
sudo mount -t virtiofs com.apple.virtio-fs.automount /mnt/shared

Push VM image to OCI registry :

tart push my-local-vm acme.io/org/name:latest acme.io/org/name:v1.0.0

Create a macOS VM from an IPSW :

tart create --from-ipsw=latest tahoe-vanilla

tart run tahoe-vanilla

Downloads the latest macOS IPSW and starts a fresh VM.

CI/CD integration

Using Tart with Cirrus CLI provides a Docker‑like CI experience. Example .cirrus.yml:

task:
  name: hello
  macos_instance:
    image: ghcr.io/cirruslabs/macos-tahoe-base:latest
  hello_script:
    - echo "Hello from within a Tart VM!"
    - sysctl -n machdep.cpu.brand_string

Run the pipeline:

brew install cirruslabs/cli/cirrus
cirrus run

The process pulls the image, starts the VM, copies the workspace, executes the scripts, and collects artifacts, reproducing Docker CI behavior with a full macOS environment.

Comparison with alternative solutions

Tart – performance: near native; macOS support: full; OCI support: native; CI friendliness: very high.

UTM – performance: good; macOS support: supported; OCI support: none; CI friendliness: low.

VMware Fusion – performance: average; macOS support: supported; OCI support: none; CI friendliness: medium.

Lima/Colima – performance: good; macOS support: Linux only; OCI support: partial; CI friendliness: medium.

Docker – performance: native; macOS support: not supported; OCI support: native; CI friendliness: very high.

Adoption

Organizations reported using Tart internally, including Atlassian, Figma, Mullvad VPN, Expo, and Krisp. The GitHub repository has ~6.1 k stars and 317 forks, indicating active community interest.

Use cases

iOS/macOS development teams – cross‑version testing (macOS 12‑26) without physical devices.

CI/CD engineers – building macOS build clusters or self‑hosted GitHub Actions runners.

AI agent developers – providing isolated sandbox environments for agents such as Claude Code.

Security researchers / malware analysts – disposable, isolated VMs for analysis.

Limitations

Tart runs exclusively on Apple Silicon and requires macOS 13 or newer; Intel‑based Macs are not supported.

Speculative deployment

It is hypothesized that OpenAI may use Tart as a sandbox for AI agents, exemplified by the community project ClodPod , which creates an isolated macOS VM for Claude Code and exposes only a project directory, allowing safe execution of claude --dangerously-skip-permissions.