Thoughts on a CompactTxStreamer compatibility gate for lightwalletd and Zaino

General
1

Hi everyone,

Wanted to put this idea out here and get input from people who work on wallets, backends, or related infrastructure in Zcash.

The idea is a small tool called Zcash CompactTxStreamer Compatibility Gate.

The job of the tool would be to run a set of black-box checks against CompactTxStreamer-compatible backends like lightwalletd and Zaino and flag behavior drift on a small set of important wallet-facing gRPC methods before those changes reach downstream wallets and tools.

This is not meant to be a broad testing toolkit. It is not a devnet, not a JSON-RPC test suite, and not a performance benchmark. The scope is much narrower than that. The point is to have a small public release-check tool for a part of the stack that already has multiple implementations.

At a high level, the tool would include:

  • a small CLI runner
  • a versioned case set
  • backend profiles for lightwalletd and Zaino
  • JSON and Markdown diff reports
  • a GitHub Action for fast CI checks

For a first version, the method scope we are thinking about is:

  • GetLatestBlock
  • GetBlockRange
  • GetTreeState
  • GetLatestTreeState
  • GetSubtreeRoots
  • GetMempoolTx
  • GetTaddressTransactions
  • deprecated method handling for GetTaddressTxids
  • a few error-path checks like invalid ranges and invalid height or hash requests

The gap this is trying to fill is that there is a shared wallet-facing protocol surface with more than one implementation, but there is no small public compatibility gate for checking whether a defined set of important methods still behaves as expected across implementations after releases or protocol changes.

Would especially appreciate input on three things:

  1. Does this solve a real problem from your perspective?
  2. Is the v1 scope about right, or does it need to be tighter?
  3. Does this feel genuinely useful as a standalone tool, or too close to testing workflows that already exist?

Thanks in advance for any thoughts.

2

a solid solution to bridge the gap between backend implementations!

This is a fantastic proposal! Subtle behavior drifts between lightwallet and Zaino have always been a major headache for wallet developers. Every time a backend gets updated, it feels like carrying a ‘hidden time bomb,’ so having a tool like this would be a huge relief.

Focusing on the heavy hitters like GetTreeState and GetSubtreeRoots shows that you’ve identified exactly where the most friction occurs in practice. I really appreciate how the scope stays lean and stays focused on the essential gRPC methods - it makes the tool feel very practical and high-impact.

It feels less like just another test suite and more like a Peacekeeper that will help standardize the ecosystem. Setting this up with GitHub Actions to automatically verify compatibility will go a long way in building trust between backend maintainers and wallet developers. Truly a great initiative!

3

Hi! @oscar-pepper already developed this for rust in a previous grant for Zaino. And we are currently porting these tests to the integration-tests repo.

If you’d like to chime in development please ping me and we could figure something out for you folks to collaborate on. I’m sure @zancas and @nuttycom have good ideas.

You can also pick up ready to work issues from this board as well Projects · wallet · GitHub

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