rpcwright 🔧

A wright is a maker — a shipwright builds ships, a playwright builds plays. A rpcwright builds (and proves) Ethereum JSON-RPC.

rpcwright is an agent skill that teaches an AI agent how to implement and conformance-test a change to the Ethereum execution-layer JSON-RPC API — across the four repos that have to agree:

The one-line behavior change is easy. The hard part is the build/test plumbing and the dozen places a silent failure hides — a green hive run that executed zero tests, a fixture that passes validation only because the param was still "required", a harness quietly testing the upstream image instead of your change. This skill encodes the exact commands and those gotchas so future sessions don't rediscover them the slow way.

What's inside

• SKILL.md — the mental model, the golden-path recipe, and the gotchas that cost hours.
• references/go-ethereum.md — build, test, RPC method & optional-parameter patterns, in-process RPC test harness.
• references/execution-apis.md — OpenRPC YAML, specgen/openrpc.json, speccheck, and the required semantics.
• references/testgen.md — rpctestgen, make fill, the .io format, generating fixtures with a local client, determinism.
• references/hive.md — the rpc-compat simulator, local fixtures, building clients from source, client-files, the --sim.limit trap, reading results.
• references/clients.md — per-client handler locations and local-build notes (go-ethereum & Nethermind verified; Besu, Erigon, Reth, ethrex guidance).
• references/gotchas.md — the full catalog.
• references/worked-example.md — a complete change end to end (default an omitted block param to latest), including a real cross-client bug found and fixed.

Install

Claude Code and Codex both read the same format — a directory with a SKILL.md — so one copy serves both. Only the directory each one scans differs:

Claude Code plugin (no clone)

/plugin marketplace add MysticRyuujin/rpcwright
/plugin install rpcwright@rpcwright

Manual (personal skill)

Clone once, then symlink it into the tools you use. Both follow a symlinked skill directory, so a single git pull updates every tool:

git clone https://github.com/MysticRyuujin/rpcwright.git
mkdir -p ~/.claude/skills ~/.agents/skills
ln -s "$PWD/rpcwright" ~/.claude/skills/rpcwright   # Claude Code
ln -s "$PWD/rpcwright" ~/.agents/skills/rpcwright   # Codex

Either tool discovers the skill from its SKILL.md frontmatter and loads it when a task involves the Ethereum JSON-RPC API, execution-apis, rpctestgen/testgen, .io fixtures, speccheck, openrpc.json, or hive rpc-compat.

AGENTS.md, CLAUDE.md, and llms.txt are symlinks to SKILL.md, so a repo that vendors rpcwright at its root also picks it up as plain project instructions.

Scope

The execution-apis + testgen + hive workflow is client-agnostic. The client-specific guidance is verified for go-ethereum and Nethermind and is best-effort guidance for Besu, Erigon, Reth, and ethrex — contributions to verify and extend those are welcome.

License

MIT — see LICENSE.