ARK v0.5 | Branch-only Signing Sessions and Connector Trees
Photo by We're releasing Ark v0.5 as a maintenance-focused update that improves overall efficiency and user experience. Though the changes are incremental, they're designed to make a noticeable difference for future participants in Ark rounds, providing smoother signing sessions with fewer hassles at scale.
🆕 New Features
✍️ Branch-only VTXO Tree Signing
The new release optimizes VTXO tree signing. Previously, users had to sign the entire transaction tree, which became computationally demanding as rounds grew larger. This shift drastically cuts down on the number of signatures you have to produce, making rounds quicker and less resource-intensive. If you'd prefer to keep signing the entire tree — or delegate parts of the signing to another party — that flexibility is still there.
This streamlined approach benefits anyone who joins bigger rounds, where signing time could become a bottleneck.
🔗 Connector trees
Another notable addition is the move from a linear connector chain to a tree structure. Previously, you had to sign a forfeit transaction for every single VTXO spent in a round, which could add up quickly. Now, each VTXO only needs one forfeit transaction. This effectively lightens the load when you join a round, as you no longer have to sign multiple forfeit transactions for each of your spent VTXOs.
On the server side, this allows for a constant number of transactions to broadcast in the event of fraud, ensuring the server can react swiftly without overwhelming clients with excessive signatures.
🛠️ Optimizations
🌐 Network Compatibility and Transaction Costs
Our server implementation is now compatible with the testnet3, signet networks. Testnet4 is soon to follow once we address related dependencies.
We've also introduced an optional configuration that removes the minimum relay fee for redeem transactions, though this may prevent block inclusion in worst-case scenarios. This feature previews Ark's future functionality once Bitcoin v29 implements support for 0-value anchor outputs.
🔄 Round Processing and Client Interaction
We've tightened up server-side processing to filter out redundant and invalid actions. Now, when a clients isn't selected for a processing round, it automatically queues for the next available slot instead of consuming resources on unnecessary data transmissions.
By ignoring non-relevant transactions and signatures, the server keeps each round more predictable. This should reduce system congestion and delivers smoother performance for all users, particularly during peak usage periods.
📈 Scalability Improvements
This update also makes it easier for the server to handle larger rounds. The VTXO tree and forfeit transactions creation and verifications are faster, so users shouldn't see a significant slowdown when the participant count rises.
We've made changes to the core of the server, replacing fixed timeouts between round stages with a dynamic approach that progresses as soon as all required data is available. If participants sign quickly, the round will conclude faster—eliminating unnecessary waits imposed by arbitrary timers once everything is ready.
💻 Client SDK API Update
To make onchain operations clearer, we've replaced the old SendOnChain method with more focused functions such as OnboardAgainAllExpiredBoardings, WithdrawFromAllExpiredBoardings, and CompleteUnilateralExit. We've also introduced new naming conventions: CollaborativeRedeem becomes CollaborativeExit, and UnilateralRedeem becomes StartUnilateralExit.
For better responsiveness, there's a new GetVtxoEventChannel API that keeps you informed about changes in your VTXO set in near real time. This is especially useful if your application needs to respond quickly to state changes — like updating a user's balance display as soon as it becomes spendable.
Conclusion
Ark v0.5 is about refining the experience for active participants. By reducing the number of transactions you need to sign, speeding up rounds, and simplifying how forfeits work, we aim to lessen the overhead so you can focus on what matters. We encourage anyone who wants a more efficient Ark workflow to upgrade and share any feedback or questions you have. It's a small but meaningful step toward a more robust, user-friendly Ark.