Microsoft Execution Containers vs Modal Sandboxes

Microsoft Execution Containers

MXC puts nine operating-system sandbox backends behind one typed request, with network access denied by default and a JSON Schema for the stable 1.0.0 contract. Version 1.0.0 is two days old as of 8 October 2026. Enforcement varies by backend, and isolation_session cannot restrict networking at all.

Modal Sandboxes

GPU sandboxes at the same per-second rates as the rest of Modal. No REST API, and the JavaScript and Go SDKs are beta.

Microsoft Execution Containers

1. Import from @microsoft/mxc-sdk/v1. The package root exports nothing.
2. Call getPlatformSupport() first and stop if isSupported is false. getAvailableBackends() is advisory and launch-time validation still applies.
3. Set network.egress.default to allow only when the task needs it. Omitted network policy resolves to deny in every direction.
4. Never pass --audit to an executor for untrusted code. It turns off all sandbox security for the workload.
5. Read ExecutionResult.warnings after each run. Security warnings arrive there and are not written to stdout or stderr.

Modal Sandboxes

1. Pass timeout= when you create a sandbox. The default lifetime is 5 minutes
2. Set block_network=True or a cidr_allowlist for untrusted code
3. Give a sandbox a name so a retried create raises AlreadyExistsError instead of starting a second one
4. Snapshot the filesystem before the 24-hour limit and start a fresh sandbox from it
5. Catch ResourceExhaustedError from Sandbox.create() on SDK 1.6.0 and later