An open-source Lean Ethereum consensus client, written in Go and maintained by Gean Labs.

Gean is:

• A consensus client for Lean Ethereum, designed for fast finality, quantum-resistant security, and a simpler core protocol.
• Running on Lean Consensus devnet-4 alongside independent client implementations.
• Built for clarity and auditability, with a deliberately small codebase.
• Quantum-resistant by design, using XMSS signatures instead of BLS signatures.

• Go 1.25+
• Rust 1.90.0
• uv
• Docker

make build       # Build the Rust FFI and Go binaries
make test        # Run Go unit tests
make test-ffi    # Run XMSS FFI tests
make test-spec   # Generate and run production-scheme consensus fixtures
make lint        # Run Go and Rust linters
make docker-build

Run make help for all available targets.

For a multi-client devnet:

make run-devnet

For a three-node Gean network, run the setup once and start each node in a separate terminal:

make run-setup
make run
make run-node1
make run-node2

At least one node must run as an aggregator for the network to finalize.

Gean tracks Lean Consensus devnet-4. Consensus fixtures are generated from leanSpec@1589f871513dc44dfcb9c7db0ed367d5cec854e9 with leanMultisig f66d4a974eced803574eb0ea43d812e523c8d7ad.

Gean treats reviewability as a consensus-safety property. Consensus-critical behavior should remain small enough to audit end to end, and disagreements between clients should be traceable to a small number of files.

Gean is open-source software released under the MIT license.