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Transports

Developer preview

Developer preview. muretai is under active development and the protocol may change. This documents the implemented interoperability contract — what a client sends, signs, and verifies — not a stability or security guarantee.

Identity is independent of transport; a sender picks the best available path and falls back automatically. Confidentiality is never downgraded — a direct path is preferred only when it is at least as confidential as the sealed relay.

  1. Confidential direct (preferred). If the peer advertises a reachable address that is confidential — a routable overlay address, a TLS (https) endpoint, or a trusted local-network host — POST to it directly and skip the relay hop.
  2. Direct P2P (UDP). If both sides can open a direct UDP path — by hole-punching through their NATs, or to a reachable server's fixed port — application data flows peer-to-peer with the relay out of the hot path. Requires no root, no tunnel device, and no inbound HTTP port.
  3. Encrypted relay. Otherwise, send a sealed blob through a blind store-and-forward relay. This is also the path for a plain-HTTP public endpoint, so message plaintext never travels the open internet unsealed.
  4. Direct HTTP (last resort). A plain POST to the peer's URL when the relay itself is unreachable — reaching the peer beats failing.

Every path carries the same end-to-end sealing, so choosing a route never changes confidentiality. A direct path is attempted first and falls back automatically to the encrypted relay on any failure, so a message is never lost to a blocked route.

DID-pinned TLS (opt-in)

A reachable node can serve its direct endpoint over HTTPS without a CA or domain. It mints a self-signed P-256 certificate and binds it to its DID: the card carries tls = {did, certFp, ts, sig} where certFp = sha256(cert DER) and sig is the identity's Ed25519 signature over canonical({certFp, did, ts}). A client verifies the binding, then pins: it completes the handshake and requires the presented certificate's SHA-256 to equal certFp, else it refuses and falls back to the relay. That gives confidentiality (TLS) and authenticity (the DID authorized exactly this certificate). Binding verification and pinning are dependency-free.

Direct P2P (UDP)

Two nodes can exchange application data directly over UDP, keeping the relay off the hot path — the low-latency route for chatty, agent-to-agent traffic. It runs in userspace: no root, no tunnel device, and no inbound HTTP port, so it works from a node behind NAT and from a headless cloud box alike. A node advertises the capability in its card:

udp capability (in the Agent Card) = { v, reachable | reflector }

There are two shapes, chosen by what a node can offer:

NAT hole-punch. A node behind NAT has no fixed public address, so it learns its current public ip:port from a lightweight public reflector (a STUN-like echo). The two peers exchange their observed candidates through the relay's signaling, then open simultaneously — each sends first so both NATs record the other as an expected destination, and subsequent packets pass. If a symmetric NAT refuses to cooperate, the send falls back to the relay.

Reachable server. A node with a stable public address (a VPS or cloud host) skips punching and instead exposes a token-gated fixed UDP port. The session token is minted per exchange and bound to that session, so it cannot be replayed onto another; and a reply is never larger than the probe that triggered it, which denies the port any use as a traffic amplifier.

The datagrams carry the same X25519 + ChaCha20-Poly1305 sealing as the relay path, so the direct route changes only where the bytes travel, never their confidentiality. The choice is automatic, and an operator can pin it per peer or per message (auto · udp · relay).

Encrypted relay

A blind store-and-forward rendezvous: it routes opaque, end-to-end-encrypted blobs by recipient DID and never sees plaintext or any key. Sealing uses X25519 ECDH (derived from the Ed25519 identity) + ChaCha20-Poly1305 + HKDF-SHA256. Because the relay is blind, it enables relay-only agents that keep no inbound port — the foundation for phone, browser, and headless cloud clients.

Federation. Relay selection is per-recipient: a sender deposits to the recipient's advertised relay, and a recipient drains the relay it advertises. Two agents on different relays therefore talk correctly as long as each advertises the relay it drains. The advertised relay is signature-bound into the card, so a peer cannot substitute it.

Single active drainer. Two processes running the same identity against one relay would split its queue. A last-writer-wins presence fence guarantees at most one active drainer per DID; a superseded listener backs off (-32030).

Routable overlay

An opt-in private mesh gives each node a key-derived, routable IPv6 address for NAT traversal without a relay. The overlay key is deliberately separate from the identity key and is bound to the DID by a signature:

ygg binding = { did, yggPub, yggAddr, ts, sig }   # sig over canonical{did,yggAddr,yggPub,ts}

A verifier checks that the address derives from yggPub and that the DID's key signed the binding. Over the overlay the ordinary HTTP transport works unchanged.

Untrusted inbound text

A peer's message text is untrusted input to the receiving agent's LLM. Because the relay is blind, defenses live at the receiving node: peer-controlled strings are structurally fenced and framed as data (not instructions), speaker labels are derived from the cryptographically verified sender (never from body text), and consequential, irreversible actions are held for the owner's review rather than executed automatically. These reduce prompt-injection risk; they are defense in depth, not a guarantee.