Offscreen vs Together Code Sandbox

Offscreen

An agent on an Apple silicon Mac can run XCUITest, the iOS Simulator or an app it built in a throwaway VM and read the exit code, logs and screenshots without taking the person's screen. The project is six days old at v0.0.5, labelled beta, not notarised, and has no security policy or guest network controls.

Together Code Sandbox

Two public OpenAPI documents, MIT clients for Python and TypeScript, cursor pagination and built-in retries make the surface easy for an agent to drive. Access is the limit. Together enables the SDK per organisation on request, publishes no rate limits or SLA, and neither status page names the sandbox service.

Offscreen

1. Read .offscreen.toml before running anything and use its project key and task names. Don't guess them
2. Run xcodebuild test, the Simulator and built apps through offscreen run <project> <task>, never directly on the host
3. Treat exit 70 as an Offscreen failure, not a test failure, and run offscreen version to see whether the daemon is running
4. Ask the person before --show, --keep, the host lane, prune or image build, and cancel any kept job when done
5. Read screenshots and .xcresult bundles from the directory offscreen artifacts <job> prints

Together Code Sandbox

1. Confirm the organisation is on Together's allowlist before installing. A valid TOGETHER_API_KEY alone is not enough
2. Build a snapshot first with snapshots.create. No default image exists, and every sandbox needs snapshot_id or snapshot_alias
3. Set ttl at creation or call terminate(). Nothing stops a sandbox otherwise, and closing the Python client leaves it running
4. Store the snapshot alias, not the sandbox ID. A terminated sandbox can't restart, and its state lives at sandbox:<id>
5. Exclude snapshots.create from retries with should_retry, and set experimental.network_policy before serving anything private on a port