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Microsoft eXecution Container (MXC)

MXC is a sandboxed code execution system for running untrusted code (model output, plugins, and tools) on Windows, Linux, and macOS. It provides multiple containment backends, from OS-native process sandboxes to full VMs, behind a unified containment model and typed SDKs.

Features

  • Cross-platform: Windows, Linux, and macOS support with platform-appropriate containment backends
  • JSON-based configuration: Versioned container-creation requests and security policies
  • Multiple containment backends: ProcessContainer, Windows Sandbox, LXC, Bubblewrap, Seatbelt, MicroVM (Nanvix), Hyperlight, IsolationSession, and WSLC
  • Policy-driven sandboxing:
    • Filesystem policy: Read-only, read-write, and denied path lists
    • Network policy: Proxy support, outbound controls, and backend-dependent host filtering
    • UI policy: Clipboard, display, and GUI access controls
  • State-aware lifecycle: Provision, start, execute, stop, and deprovision persistent containers
  • Rust, .NET, and Node SDKs: Versioned APIs for one-shot and state-aware execution
  • Diagnostics: Tools to understand access-denied failures in a container

What is MXC?

MXC is an SDK dependency that builds into your app.

flowchart LR
    App["Your application<br/>Launch API"] --> SDK["MXC SDK<br/>Rust / .NET / Node<br/>(in process)"]
    SDK --> Backend["Selected backend<br/>(in process)"]
    Backend --> Container["Isolated workload<br/>ProcessContainer / WSLC / Bubblewrap / ..."]
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Your application specifies:

  • The container type
  • The containment rules
  • The workload command

MXC validates the request, selects the backend, and launches the workload in the resulting container.

What container types are supported?

MXC runs workloads through platform-appropriate container backends on Windows, Linux, and macOS.

Runtime platform Default backend Other backends Minimum host OS
Windows 11 x64 / ARM64 processcontainer windows_sandbox*, wslc, microvm*, hyperlight*, isolation_session Windows OS-version support
Linux x64 / ARM64 bubblewrap lxc, microvm, hyperlight -
macOS ARM64 / x64 seatbelt - -

* These backends are experimental.

How do I use MXC?

Install an SDK through your package manager. You do not need to clone this repository.

SDK Package
Rust https://crates.io/crates/mxc-sdk
.NET https://www.nuget.org/packages/Microsoft.Mxc.Sdk
Node https://www.npmjs.com/package/@microsoft/mxc-sdk

The Node and .NET packages include the native runtime assets. The Rust crate builds the MXC SDK, engine, and selected backends into the consuming application.

Non-SDK consumption: Platform-specific executor binaries, such as wxc-exec.exe, accept JSON container-creation requests defined by the stable schema. Use for testing or when the SDK cannot be embedded in your app.

Running a contained workload

For complete SDK samples, see the Rust, .NET, and Node samples.

Sample Node snippet

import { spawn, type ContainerRequest } from '@microsoft/mxc-sdk/v1';

const request: ContainerRequest = {
  command: 'node -e "console.log(\'hello from container\')"',
  network: { egress: { default: 'deny' } },
  timeoutMs: 30_000,
};

const child = await spawn(request);

See the runnable streaming standard-I/O sample and the SDK API reference.

My application won't run in the sandbox!

Your application will hit access issues when running in a sandbox, until you've had time to tune your containment rules. We're here to help.

Debug console mode

Native executors normally reserve standard input, output, and error for the workload. Use --debug for MXC diagnostic output:

wxc-exec.exe --debug config.json

See MXC diagnostics for the complete developer reference.

Audit mode

Warning: --audit turns off all sandbox security for the workload being analyzed. Never use it to run untrusted code.

Audit mode helps a policy author find access-denied failures and reconstruct a ProcessContainer policy that grants the files and capabilities a trusted tool actually needs. On supported Windows releases, run:

wxc-exec.exe --audit policy.json

MXC records the observed accesses and produces policy-authoring artifacts. See logging access denied for safe deny-and-record diagnostics, audit outputs, and supported workflows.

Telemetry

Official Microsoft builds can send optional diagnostic telemetry to Microsoft. Telemetry is off unless the individual run opts in, the Windows user has explicitly consented, administrative policy permits collection, and your application enables the telemetry option in a contained workload request. An administrator can block telemetry but cannot grant consent for the user.

Local open-source builds are not configured to route telemetry to Microsoft, and telemetry is a no-op on non-Windows platforms. See telemetry policy and consent for controls and privacy details.

Building from source

Build from source when developing MXC, changing the native runtime, or using the standalone executor binaries instead of a packaged SDK. Repository builds produce the platform-native runtime and executors and stage the native assets used by the Node SDK.

Build prerequisites are:

  • Rust, pinned to version 1.93 by src/rust-toolchain.toml
  • Node.js 24 or later and npm
  • The platform toolchain and prerequisites described by the selected backend

Build

Windows

build.bat --all             # Release build for current architecture

Linux

./build.sh --all            # Release build

macOS

./build-mac.sh --all        # Release build for native architecture

Documentation

Consumer documentation

Document Repository location Purpose
SDK samples samples/ Runnable Rust, .NET, and Node scenarios
SDK API reference docs/api-reference/ Supported V1 operations and types
Container lifecycle docs/container-lifecycle.md Persistent container lifecycle overview
Logging access denied docs/logging-access-denied.md Diagnose blocked accesses and author policy
Telemetry docs/telemetry.md Consent and administrative controls
Backend guides docs/backends/ Platform and backend prerequisites and behavior

Repository contributors should start with the MXC development documentation.

Contributing

See CONTRIBUTING.md for contribution guidelines.

License

See LICENSE.md for details.