Fukuii

Fukuii is an execution client. It holds a copy of the chain, checks every block against the rules, keeps the account state that results, and answers questions about it over a public interface. That is the job every node on the network is there to do.

What makes it unusual for Ethereum Classic is where it came from. Every client this network has run until now began life as an Ethereum client and had Ethereum Classic support added to it afterward. Fukuii was written for Ethereum Classic from the start, which is why it is described as the first client native to this network.

It is written in Scala 3 and runs on the Java Virtual Machine. That choice is not incidental: the language's type system makes a class of consensus mistake impossible to write down, so it is caught when the code is compiled rather than when a block is processed.

Consensus is selected per deployment and sits behind a single interface, so the rest of the client does not change when that choice changes.

On Ethereum Classic and Mordor that is native Proof-of-Work. Fukuii implements ETChash and the ECIP-1099 epoch schedule, and it serves the work interface that mining software connects to, so it can be the node behind a mining operation rather than only a node beside one.

On Proof-of-Stake networks it can run a consensus layer inside the same process, which makes a node one thing to deploy instead of two. That is an option rather than a requirement: the Engine API is implemented either way, so an external consensus client can drive Fukuii instead.

Fukuii is maintained by The Fukuii Authors, an organization whose members are Chippr Robotics LLC and White B0x Inc. The authors maintain the repository, review what lands in it, and publish the releases. There is no foundation or steering body sitting between the code and the people who are accountable for what it does.

Development happens in the open on GitHub. Changes arrive as pull requests and ship in tagged releases, and each release carries a build signature and a software bill of materials, so a running binary can be traced back to the commit and the build that produced it. The license is Apache 2.0, which permits commercial use, modification and redistribution, and carries a patent grant from the contributors.

The authors' work extends past the client itself: they include a credited contributor to the EEA Enterprise Ethereum Client Specification, the document that sets out implementation requirements for Enterprise Ethereum clients. That is a contribution to the specification, and it is not a conformance claim about Fukuii itself.