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Star-shaped head network

Design proposal

This topology describes an application built from independent heads. Hydra provides the individual heads; it does not provide routing or atomic payments between them.

A service can participate in a separate two-party head with each client. It runs a hydra-node process for each head. Clients and the service must remain available to sign snapshots in their respective heads.

Alice and Bob each run a head with a separate node instance at the same service.

Funding and settlement​

Each head opens empty and receives its own deposits. The same L1 input cannot fund two heads: each deposit spends distinct inputs. Heads maintain separate UTxO sets, snapshot signatures, and settlement transactions.

Two independently funded heads connect Alice and Bob to a service; cross-head coordination belongs to the application.

A service needs liquidity in both heads and an application protocol to move economic value between them. An atomic transfer mechanism, its timeouts, and failure recovery must be designed separately. Copying a transaction or snapshot from one head to another does not provide these guarantees.

Off-chain coordination​

Each head uses its own snapshot leader rotation and requires signatures from all its parties. The service is not permanently the leader.

An application submits separate transactions to two heads; each head independently confirms its own snapshot.

The illustrated sequence is not an atomic payment protocol. A complete design must explain what happens if either head stops progressing, closes, or loses its required liquidity between the two confirmations. Each head can close and settle independently; any coupling must be enforced by the application.