Four additions, all constants, none on the resolution path: sync.getRepoStatus, sync.listRepos, sync.listBlobs and _health. Shapes copied from a live reference PDS rather than invented, and verified to match it byte for byte in structure. They exist so a mirror or crawler that already knows the hostname meets a well-formed host instead of a wall of 404s. `active` is always true, the repo list is always one entry, the blob list is always empty — an empty list being the truthful answer for a project where blobs are a non-goal, and better than a 404 a mirror would read as the host being broken. _health is the exception to the caching rule at no-store: a liveness probe answering from cache is not a liveness probe. It reports the Corpora version that built the bundle, since nothing is running that could have a version of its own. What this deliberately does not add: subscribeRepos and requestCrawl, which need a live process and a firehose; describeServer, because claiming to be an account server would mislead; and resolveHandle, because an authority has no handle. All four still answer MethodNotImplemented, and there is a test asserting subscribeRepos continues to. None of this makes the authority relay-indexable — that needs requestCrawl followed by a firehose a relay can follow. The RELAYS.md links added here are pending that research. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>