E2B vs Offscreen

E2B

Firecracker microVM with its own kernel per sandbox. Two major incidents over an hour in September 2026, on sandbox creation and on creating from snapshots.

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.

E2B

1. Set a timeout when you create a sandbox. The default is 5 minutes
2. Pause rather than kill when you'll come back. Resume takes about a second and nothing is billed while paused
3. Use Secret.fill in network transforms instead of passing API keys into the sandbox environment
4. Pace sandbox creation. Hobby allows 1 a second and 20 running at once
5. Move to the v2 sandbox endpoints. SDK 2.51.0 and later use them by default

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