Lodestar Roadmap and Vision 2025 (Updated Jul 2025) 🌟

*This is a living document and subject to change.*

This issue outlines the new roadmap for Lodestar based on the announcement made in June 2025 to [blend Zig and JavaScript for a high-performance Ethereum client](https://blog.chainsafe.io/lodestar-zig-and-javascript/).

# Overview
The Lodestar team is planning a significant strategic shift in their development approach, moving towards using the Zig programming language in core modules and the Bun JavaScript runtime to improve performance and ensure the client remains on Ethereum's critical path.

## Mission 2025
Transition from a pure JavaScript client focused on browser compatibility to a performance-first, hybrid JavaScript and Zig architecture.

## Vision
Key motivations for this transition contributing to our vision for Lodestar:
- Performance improvements and memory efficiency through Zig native libraries
- Zig is more performant and memory-efficient than JavaScript (see #7237 as an example)
- Easier to interface with C libraries compared to other languages
- Provides programming patterns that enable more efficient code executio
- Allows for compile-time optimizations that can significantly improve performance
- Better positioning on Ethereum's critical path to [scale L1, scale blobs and improve UX](https://protocol.ethereum.foundation/)
- Preparation for future developments and support current research initiatives like the Beam chain (See: [Lean Ethereum](https://www.youtube.com/live/EvYRiFRYQ9Q?t=5407s))
- Maintaining performance competitiveness with other clients as the Ethereum roadmap accelerates
- Contribute to developing the Ziglang developer ecosystem and maturing dev tooling for the language and Ethereum

# Implementation
*July 2025 planned stack overview*

**Zig Libraries**
- ssz-z: https://github.com/ChainSafe/ssz-z
- blst-z: https://github.com/ChainSafe/blst-z
- snappy: https://github.com/ChainSafe/snappy
- hashtree-z: https://github.com/ChainSafe/hashtree-z
- zig-discv5: https://github.com/ChainSafe/zig-discv5
- zig-libp2p
- zig-libp2p-quic: TBD
- zig-libp2p-gossipsub: TBD
- bun-ffi-z: https://github.com/ChainSafe/bun-ffi-z
- state-transition: https://github.com/ChainSafe/state-transition-z
- fork-choice: TBD
- zbuild: https://github.com/ChainSafe/zbuild

### Workstreams provide high level categorization of parallel development streams. Not ordered by priority.

## Workstream 1: Bun Runtime (Lodestar v2.0)
*Reference: #7280 and #7867*

**Goals:**
- Prove zig+bun hybrid and use everywhere
- Tackle any blockers for Bun integration
- Complete checklist #7993 and release Lodestar v2.0

## Workstream 2: Zig Consensus Logic
*Depends on Workstream 1: Improve performance with Zig and rearchitect beacon node on bottlenecked functionality by priority*

**Goals:**
- Write, expose and swap a napi binding (we will use napi as a default and only expose bun-ffi wrapper if there are performance considerations)
- Zig native replacement for state-transition
- Zig native replacement for fork-choice
- Zig native replacement for gossip validation

## Workstream 3: Re-architecturing Beacon Node
*Depends on Workstream 2: Unlocking potential restructuring of the beacon node for better resource consumption. More to follow as ideas develop*

**Goals/Ideas:**
- Use parallelism in gossip validation
- Share state memory across workers

## Workstream 4: Zig Networking
*Preparations for switching to a Zig native libp2p networking stack*

- Networking
- Contribute to zig-libp2p QUIC implementation
- Contribute to zig-libp2p gossipsub implementation
- Develop zig-discv5

## Workstream 5: Client Research & Experimentations
*Discover and re-shape Lodestar roadmap based on new experimentation and results for improvements. More to follow as ideas develop*

**Goals/Ideas:**
- Experiment with https://github.com/mratsim/constantine (awaiting audit)
- Research boot time speedup
- QUIC experimentations with EF p2p team

## Workstream 6: Ethereum Research and Development Implementations
*Continue client implementations for development of the Ethereum protocol roadmap*

**Goals:**
- Implement, discuss, debug, ship Fusaka features
- Continue contributing to specifications and research for Ethereum L1 protocol
- Participation in research and testing calls for Glamsterdam and beyond
- Implementing experimental features such as FOCIL for research & development of Ethereum
- Implement block and blobs backfilling