· Lean Consensus Client

Minimalist.
Fast.
Modular.

ethlambda is a minimalist, fast, and modular implementation of the Lean Ethereum consensus client, built by LambdaClass with deep expertise in distributed systems and blockchain infrastructure.

Open source · MIT license · Built and maintained by LambdaClass

Current devnet pq-devnet-4
Working on pq-devnet-5
License MIT
~/ethlambda · zsh
$ make run-devnet
→ cloning lean-quickstart… ok
→ building docker image… ok
→ generating genesis files… ok
→ starting all clients… ok
$ ethlambda --is-aggregator
peers · 4  ·  block #00047021
attestations aggregated  ·  finalized

Project Highlights

Why ethlambda
Full Lean Consensus Compatibility

A cutting-edge consensus client for the next iteration of the Beacon Chain: the Lean Chain.

Built by Experts

Developed by LambdaClass, the team behind ethrex 🦖, the production-ready Ethereum execution client.

Minimalist by Design

Less than 10k lines of Lean code with low abstraction: easy to maintain, read, and audit.

Community-Driven

Fully open-source, with an active dev team and contributions welcome.

Current Status

PQ Interop · Devnet Progress
History
Oct 2025

pq-devnet-0 Completed

Goals
  • Create leanSpec framework
  • Multi-client coordination (no PQ sigs yet)
  • Interop trials: 4s slots, QUIC, Gossipsub v1.0
  • Apply modified 3SF-mini consensus mechanism
Dec 2025

pq-devnet-1 Completed

Goals
  • Integrate leanSig signing & verification
  • Apply basic signature aggregation (by concatenation)
  • Baseline performance metrics for PQ signing & verification
Jan 2026

pq-devnet-2 Completed

Goals
  • Integrate leanMultisig aggregation
  • Baseline performance metrics for PQ signature aggregation
Feb 2026

pq-devnet-3 Completed

Goals
  • Decouple aggregation from block production via separate aggregator role
  • Establish protocol for propagating aggregated signatures
  • Create foundation for different aggregation/propagation strategies
Active

pq-devnet-4 Active

Goals
  • Enable recursive PQ signature aggregation using leanVm
  • Coalesce multiple aggregates for the same message into one final aggregate
  • Ensure blocks contain a single aggregate per message
Planned

pq-devnet-5 Planned

Goals
  • Produce one block-level aggregation proof covering multiple attestation messages
  • Leverage proof decomposability so per-message proofs remain recoverable
  • Replace 3SF-mini with PQ heartbeat: committee-based voting under Goldfish fork-choice

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