Hydra advisory fix changes head scripts and requires coordinated upgrades.

What happened.

Hydra merged a fix associated with GHSA-f825-9gwc-h5xq that its commit describes as breaking. The change alters the signed snapshot message, the close, contest, increment, and decrement redeemers, and the head validator script hash.

A subsequent merged commit regenerated the head script. Together, the records indicate that the fix changes Hydra’s on-chain compatibility surface rather than being a routine node-only update.

Why it matters.

For Hydra head participants and integrators, the upgrade is an all-party operational event. Parties in the same head need to move together because the new script hash and changed messages and redeemers must match.

Existing heads are the immediate constraint: a new node cannot close a head opened on the previous scripts. Operators may therefore need to close or drain old heads before reopening or operating under the new scripts. Tooling that constructs or verifies the changed messages and redeemers also needs to match the updated commitment format described in the research record.

What to watch.

The next useful receipt is a Hydra release cut or release announcement carrying these merged changes. The supplied record says the work is on the development branch and does not provide a release tag, version number, deployment schedule, or evidence of a mainnet deployment.