Hydra protocol v2 flags a coordinated upgrade requirement

What happened.

Hydra’s perf-2 change batches etcd broadcast into a single Raft commit per revision and bumps the Hydra network protocol to version 2. The change is marked BREAKING because mixed-version heads cannot exchange messages: older nodes drop the batched values.

This work is part of a same-day set of five Hydra changes described as a “10x-perf” stack, alongside benchmark infrastructure, a larger snapshot cap, off-loop event encoding, and an incremental rust-FFI commitment. The supplied record does not establish the performance outcome of the combined work.

Why it matters.

For operators running Hydra head participants, the practical implication is an eventual coordinated upgrade window. Once the change reaches a release, participants will need to run the same compatible version for heads to continue exchanging messages.

The change concerns head-internal message exchange. It is not described as a Cardano mainnet consensus change, and it should not be read as one.

What to watch next.

Watch for a Hydra release that includes the protocol v2 change, plus release notes or operator guidance on upgrade sequencing. That is the receipt needed to determine when a coordinated migration becomes operationally relevant.