Cardano’s Hydra Gets Ready for Bigger Heads

The Hydra team merged a change that raises the maximum number of transaction outputs a Hydra Head can account for in a snapshot from 4,095 to 32,767. The team made the change in response to a developer’s request during the week of November 2–8. Essential Cardano included it in its November 13 development report.

What the Higher Hydra Limit Covers

A Hydra Head is a channel where a group of participants can process Cardano transactions off-chain. As transactions spend existing outputs and create new ones, participants agree on snapshots that capture the Head’s updated state. An unspent output can hold ADA or other Cardano assets and serve as an input to a later transaction.

The higher limit gives an application that maintains many separate outputs more room within a single Head. The limit counts both the outputs already in the Head’s unspent set and those associated with pending deposits and withdrawals. That means an application approaching the cap also has to account for changes already in progress.

Hydra Reserves Space Before Participants Confirm a Snapshot

The team also fixed a problem that could stall a Head near its capacity limit. A transaction could pass a node’s local ledger checks and push the Head beyond the number of outputs it could support. When participants rejected the resulting snapshot request, subsequent snapshots could stall.

Hydra now reserves capacity for pending deposits and withdrawals as it builds a snapshot. If a deposit would exceed the available capacity, Hydra defers it. A node can still report that a transaction passed its local ledger checks. Confirmation comes when participants include the transaction in an agreed snapshot.

[NEWSBREAK]

The Higher Limit Is Pending a Hydra Release

The capacity increase uses a larger set of cryptographic parameters from Ethereum’s KZG ceremony. The Hydra team marked the switch as a breaking change for the next release.

As of November 15, the project’s GitHub repository still lists Hydra 2.4.2, published October 22, as its latest release. The 32,767-output limit is in the development code and has yet to ship in a Hydra release.