Silius

The challenge

Ethereum's ERC-4337 account abstraction standard needs bundlers: off-chain infrastructure that validates user operations, maintains an alternative mempool, and submits them on-chain. Running this reliably across many EVM networks demands memory-safe, efficient, and modular software that operators can shape to their own deployments rather than a monolithic black box.

What we built

Lutra Labs built Silius, an ERC-4337 (account abstraction) bundler implemented in Rust. The architecture is split into independent components — a user operation mempool, a bundling component, and a JSON-RPC server — each shipped as a reusable Cargo crate so operators can run only what they need or embed pieces into their own projects. Silius implements the ERC-4337 eth and debug RPC namespaces, validates user operations via an execution client's debug_traceCall, and includes a libp2p/discv5-based P2P layer for peer-to-peer mempool propagation between bundler nodes. It runs against Geth or Erigon and is dual-licensed under Apache 2.0 and MIT.

Highlights

• Modular design: separate mempool, bundler, and JSON-RPC components, each a reusable Rust crate
• Implements the ERC-4337 v0.6.0 entry point and eth/debug RPC namespaces
• Tested across 17 EVM network configurations including Ethereum, Polygon, Optimism, Arbitrum, Base, BSC, Linea, Avalanche, and Blast (plus testnets)
• P2P mempool propagation built on libp2p and discv5 discovery
• Runs against Geth or Erigon via debug_traceCall for user operation validation
• Runs the official eth-infinitism bundler spec tests in CI; ships native and Docker deployment paths

Tech stack

• Rust
• Ethereum
• ERC-4337
• EVM
• libp2p
• discv5
• revm
• alloy / ethers-rs
• gRPC
• JSON-RPC
• Docker