Verify Harbor tasks in a separate sandbox

May 15, 2026 · The Harbor Team

Starting today, you can verify Harbor tasks in a separate sandbox from the one used by the agent. In task.toml, you can specify artifacts to copy between the agent sandbox and verifier sandbox. Verifying in a separate sandbox:

enables different resource configurations or dependencies than the agent sandbox
lets users pre-bake dependencies into a verifier image to avoid flaky package installation
provides an additional security boundary between the agent and the verification process

It also introduces constraints:

verification is limited to copied artifacts, not full container state such as running processes
tasks must explicitly write anything the verifier needs to an artifact path

Separate verification works for both single-step and multi-step tasks. Multi-step tasks can opt into a separate verifier sandbox per step. To start using this feature, update the create-task skill:

npx skills add harbor-framework/harbor --skill create-task

Or add the following sections to your task.toml:

artifacts = ["/tmp/answer.json"]

[verifier]
environment_mode = "separate"

You can also configure the verifier sandbox:

artifacts = ["/tmp/answer.json"]

[verifier]
environment_mode = "separate"

[verifier.environment]
network_mode = "no-network"  # baseline; [verifier].network_mode is an optional phase override
cpus = 2
memory_mb = 4096

Per-step verifier config uses [steps.verifier] and [steps.verifier.environment] with the same rules. Opting in treats the tests/ directory as an environment directory, similar to environment/. As usual, we’re excited to see what you build and welcome feedback!

Announcements

Earlier announcements

Verify Harbor tasks in a separate sandbox