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August 2023

· 6 min read
Pascal Grange
Sasha Bogicevic
Franco Testagrossa
Sebastian Nagel

This report summarizes the work on Hydra since July 2023. It serves as preparation for the monthly review meeting (see slides and recording), where the team updates project stakeholders on recent developments to gather their feedback on proposed plans.


This month, the team released version 0.12.0, and the project roadmap has been slightly updated to focus 0.13.0 on network resiliency and bump incremental commit and decommit in priority:

The roadmap with features and ideas

The latest roadmap with features and ideas

Release 0.12.0

  • Support cardano-node 8.1.2

    • Updated client and Plutus versions
  • Layer 2 protocol changes

    • Authenticated messages
    • Removed redundancy
  • Event-sourced persistence

  • New API endpoints

  • Removal of internal commit endpoint

  • Improved off-chain transaction processing performance

  • Security fixes

  • See full release notes and a list of delivered features


Issues and pull requests closed since the last report

This month, the team worked on the following:

Update the tutorial and include Mithril #997

To prepare for the Hydra master class at RareEvo, the team has taken the originally written tutorial for Hydra version 0.8.0 and updated it to work with the latest versions.

The challenge was to write content that is both easily comprehensible and functional across a wide range of user platforms, including operating system and processor architectures.

Besides writing the tutorial, it is essential to ensure that it is kept up-to-date (eg, using continuous integration).

Support cardano-node 8.1.2 #1007

To be able to use the latest Mithril snapshots to bootstrap a cardano-node for the hydra-node, we needed to make some updates.

The hydra-node uses the cardano-api to establish a connection with the node using the node-to-client protocols. The format there has slightly changed (although versioned), necessitating an update to the version of cardano-api used within the hydra-node.

The way Haskell dependencies are managed required an adjustment of the versions for both cardano-ledger and plutus. These versions are used to construct our off-chain ledger and on-chain Hydra Head protocol scripts, respectively.

As a result, this process has proven to be more intricate than it might initially sound. However, it has ultimately resulted in enhancements to the efficiency of our on-chain scripts.

TODO: how much?

Event-sourced persistence #913

We want the hydra-node to be efficient in processing events to yield high throughput on processing transactions off-chain.

Work done as part of #186 has demonstrated that the primary bottleneck to faster transaction processing inside the node was the state persistence logic, which simply overwrites the full state with whatever new state has been produced.

For that reason, we changed the persistent state to a sequence of events according to ADR24. Persistence is now done incrementally by saving only the StateChanged deltas.

As a consequence, the first spike confirmed the following performance improvements: master ~300ms → spike ~6ms.

TODO: what are the numbers on master before/after?

Finally, this also opens up interesting possibilities for state observation in clients.

New API endpoints

This release also includes several additions to the Hydra API. We added the /cardano-transaction endpoint to submit a transaction to the layer 1 network. This feature improves developer experience as Hydra clients do not need direct chain access (eg, connect to cardano-node) to be able to submit transactions.

The other new /protocol-parameters endpoint serves the currently configured protocol parameters used in hydra-node. This provides more flexibility when creating transactions for the head on the client side and avoids configuration or hard-coded values.

On top of this, we also included the hydra-node version inside of the Greetings message. This is very useful for debugging purposes and detecting possible version mismatches.

Removal of 'internal commit' endpoint #1018

In the previous release, we made an announcement regarding the deprecation of committing to the head through the websocket command. Subsequently, we have taken steps to eliminate this client command, which in turn resulted in the removal of the fuel markers that were previously used to mark the UTXO of the internal Hydra wallet meant for use in the Head.

This simplifies the setup needed to run the Head protocol and improves security since users can directly commit funds from their wallets without sending them to the Head operator beforehand.


Hydra master class at RareEvo

We were happy to run a Hydra master class session at RareEvo 2023. The session attracted 30+ attendees for the introductory parts including a presentation on Hydra and Mithril. About 10-15 participants remained for the practical part and following discussion.

We also streamed the event live on Discord, but were not able to interact much there. The responses were positive though and we should be doing more things in the public on this #hydra-live channel.

Several participants managed to use Mithril and synchronize a pre-production cardano-node; two teams effectively initiated Hydra heads, conducted fund transactions within them, and subsequently closed them. The major challenges, as expected, concerned installation and networking. In the future, we intend to ensure the availability of prebuilt binaries catering to a wider range of platforms.

Catalyst Fund10

The team screened all the proposals mentioning Hydra and Mithril. We submitted 11 community reviews and noticed, in particular, the following proposals:


The monthly review meeting for August 2023 was held on 2023-08-23 via Google Meet with these slides and the recording, 'broadcasting live from warm and sunny Colorado'!

It has been an interesting and unusual month. Some of the team had been in Longmont, CO to prepare for the RareEvo event and we used the chance to have the meeting in a hybrid setting with some IO stakeholders attending live on-site and about 20 community members online.

This time, the demo was about the updated tutorial and demonstrating the full setup of the cardano-node, opening a Hydra head on the pre-production network, and submitting transactions off-chain in 15 minutes!

The feedback we received included inquiries about the timing, method, and extent of the audit for the Head protocol. While we will have an internal audit, which is already helping us improve the protocol, there are no plans for a significant external audit with funding. We also had the chance to look into and learn about some Catalyst Fund10 proposals involving Hydra. Hopefully, some or all of them get funded and we are looking forward to testing the Hydrazoa concept, implementing the ledger-mode operation, enabling federated Heads, and achieving other objectives.

At the RareEvo event, we had the chance to meet and communicate with various people from the community. This ranges from known Hydra collaborators to tech-savvy stake pool operators, to representatives of successful applications running on Cardano for scaling purposes like

Also with a new full-time contributor on board, we are keen to add more functionality while the first applications prepare to utilize Hydra in production on mainnet.