Host runtime settings

Admin Settings defines defaults for every host; an individual server’s settings can override them. The effective values arrive on its next heartbeat. The runner hands each turn a validated snapshot, and pushes sandbox manager settings to its separate sandbox manager. Clearing an admin override restores the built-in default. Environment variables supply bootstrap values only until the first settings answer arrives.

The complete registry, labels, units, scopes, and validation ranges live in cloud_agent_shared/host_settings.py. The admin UI reads that registry rather than maintaining another list.

Storage reserve for new sandboxes (storage_min_available_mib) is a runner setting with a default of 1024 MiB and a range of 1–1,048,576 MiB. Its bootstrap variable is AGENT_STORAGE_MIN_AVAILABLE_MIB. Before accepting a turn that would allocate a sandbox, the runner reads fresh available space through the existing attested Docker writable-layer storage probe. A reading below the reserve declines the untouched turn; the server’s launch error describes the pressure and suggests freeing storage or adjusting this setting. Existing retained sandboxes can resume and cleanup stays available.

This guard is not a quota or space reservation. Unknown, disabled, unavailable, unsupported, or unverified capacity remains explicitly unmeasured and does not establish a storage-pressure verdict. See storage measurement and attestation and host execution limits for operational boundaries.