Introduction

ethlambda is a minimalist, fast and modular implementation of the Lean Ethereum consensus client, written in Rust.

This book collects the design notes and operator-facing references for ethlambda. It is split into two parts:

• Consensus explains the algorithms ethlambda implements: the 3SF-mini justification and finalization rules, and the LMD-GHOST fork choice algorithm. Both documents are implementation-agnostic; ethlambda-specific behaviour is called out in blockquotes.
• Operations documents observable surfaces of a running node: Prometheus metrics, checkpoint sync, and the fork choice visualization served by the API.

For build and contribution instructions, see the README and CONTRIBUTING.md in the repository.

Visual references

Two standalone HTML infographics ship alongside this book and are copied verbatim into the rendered output:

• 3SF-mini infographic
• ethlambda architecture infographic

Community

• Telegram: ethlambda group, where we post daily updates; drop by to ask questions or chat about anything Lean-related.
• X (Twitter): @ethlambda_lean for occasional updates.
• Weekly community call: every Friday, streamed live on @class_lambda; the call link is posted on Telegram beforehand.
• Ecosystem coordination: the PQ Interop calls on ethereum/pm cover cross-client Lean Ethereum work and related updates; the meeting links are posted on each issue.

Related projects

ethlambda is one of several Lean Ethereum consensus clients under active development. For comparison and cross-client testing:

• zeam (Zig)
• ream (Rust)
• qlean (C++)
• grandine (Rust)
• gean (Go)
• Lantern (C)