Walnut provides an open‑source debugging and transaction‑simulation platform for smart contracts on CairoVM and EVM rollups. It records full opcode‑level execution traces, offers a sandbox to replay and modify transactions, and includes gas profiling with flamegraph visualizations, available as self‑hosted Docker or SaaS.
Funding
Funding not disclosed
Founders
Product
Problem
Developers building smart contracts on Starknet, Cairo, and emerging EVM rollups lack native debugging and transaction‑simulation tools. Without precise traceability, diagnosing nested calls, calldata errors, or gas inefficiencies requires manual instrumentation and repeated on‑chain testing. This slows iteration cycles and increases the risk of costly deployment bugs.
Solution
Walnut delivers an open‑source debugging and simulation stack that integrates directly with the CairoVM and EVM bytecode environments. The platform records full execution traces, exposing memory, stack, and storage states at each opcode step, enabling developers to step through transactions offline. A sandbox simulator lets users replay and modify transactions with custom calldata before committing on‑chain, while built‑in gas profiling generates flamegraph visualizations for cost optimization. Walnut can be deployed as a self‑hosted Docker service or accessed via a SaaS dashboard, supporting any RPC endpoint and offering API hooks for CI pipelines. By centralizing trace data and analytics, Walnut reduces the feedback loop between code changes and performance verification, helping teams ship reliable contracts faster.
Target Audience
The primary users are smart‑contract developers and engineering teams building DeFi protocols, blockchain games, and infrastructure projects on Starknet, Cairo, and compatible EVM rollups.
Features
- Full‑stack transaction tracer with opcode‑level memory, stack, and storage inspection for Cairo and EVM bytecode
- Sandbox transaction simulator that allows calldata mutation, replay, and deterministic outcome verification
- Gas profiler with flamegraph output and per‑call cost breakdown to identify optimization opportunities
- Multi‑chain RPC‑agnostic connectivity, enabling debugging on Starknet, Optimism, Arbitrum, and other rollup networks
- Self‑hostable Docker deployment and SaaS option, both leveraging the same open‑source core
- Extensible plugin architecture and CLI/REST API for integration into CI/CD pipelines and custom tooling
- Real‑time error monitoring (beta) with configurable alerts for failed transactions or abnormal gas usage