Link your platformed accounts to an Atmosphere account.
Each linkage is stored as a pair of records on atproto PDSes, so it survives portable.agency disappearing and can be verified by anyone.
agency.portable.membership collection.agency.portable.attestation) on portable.agency's PDS — a third-party statement that your DID owns the linked account.agency.portable.membership) on your own PDS — a self-claim naming portable.agency as the attester.service block. Matching them is the proof.
Record keys are deterministic (hash of did + type + community + identifier), so re-linking the same account is idempotent, but linking multiple accounts on the same platform creates separate records. We store no session-level state beyond the in-flight OAuth handshakes.