Strong boundaries, candid limitations.

Current protections

• Auth v2 binds short-lived access and rotating refresh credentials to an enrolled device DPoP key. Replayed DPoP proofs and retired protocol generations fail closed.
• Signed device-manifest lineage lets friends pin identity continuity. After explicit in-person verification, unexpected forks, rollbacks, or incarnation changes block rather than silently replacing a key.
• Messaging v2 uses the reviewed ratcheting transport selected by the project, with per-device sessions, bounded replay state, and generic wake-only push notifications. Message plaintext is not exposed to the service.
• Presence v3 derives short-lived friend-specific values from daily pairwise seeds carried over messaging v2. Foreground-only Hat sessions last no more than one hour; successful probing is bounded and creates target-visible found-nearby evidence.
• The durable relational schema intentionally has no coordinates, raw geographic cells, presence equality material, or message-history columns. Provider retention remains a separate disclosed limit.

Known limitations

Before in-person verification, a malicious server can substitute a first-use manifest independently to each party. A malicious authorized friend can retain their daily seed, choose cells within the bounded probe budget, collude with other mutual friends, lie about their own location, and disclose a successful result. A compromised active endpoint can expose current plaintext and state. Push, network, auth, and hosting providers still observe bounded routing, timing, and participation metadata.

The post-Fable architecture is integrated into the development baseline and the integrated candidate passed whole-repository certification. JauntyHat is still pre-release: physical Secure Enclave/StrongBox behavior, production app-link association, signed release artifacts, provider operations, and formal release assurance remain to be validated. It must not be represented as release-ready.