Run the sidecar

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The sidecar is a TypeScript node for EIP-8141. It exposes eth_sendFrameTransaction, validates and simulates transactions against an execution client, relays them on chain, and gossips them to other sidecars over libp2p.

There is no EntryPoint and no eth_sendUserOperation. It needs an execution client that implements EIP-8141. Today that is the eip8141-tracer branch of ethrex. A standard client such as geth cannot validate or simulate Frame Transactions.

The sidecar is a fork of Etherspot’s Skandha, which was an ERC-4337 bundler. The reference repository is mempool-workshop-sidecar.

From source

bun install
bun run build
cp config.json.default config.json

Edit config.json:

• Point rpcEndpoint and rpcEndpointSubmit at an EIP-8141-aware execution client.
• Set relayers to the private key or keys that will submit transactions on chain.

Then start the node:

./skandha standalone

The RPC API is available at http://localhost:14337/rpc/.

With Docker

cp config.json.default config.json
# edit config.json
docker build -t skandha .
docker run \
  --mount type=bind,source="$(pwd)"/config.json,target=/usr/app/config.json,readonly \
  -dp 14337:14337 \
  skandha standalone

Modes

Mode	Command	Description
Standalone	./skandha standalone	RPC, validation and relaying. No p2p.
Node	./skandha node	The same, plus the libp2p gossip network. See P2P mempool.

Required configuration

entryPoints, canonicalEntryPoint and supportedMempools[].entryPoint must all be set to the fixed EIP-8141 sentinel address 0x00000000000000000000000000000000000000aa. It is not a deployed contract. Leaving one of them at a stale ERC-4337-style address silently disables gossip publishing in node mode.

{
  "entryPoints": ["0x00000000000000000000000000000000000000aa"],
  "canonicalEntryPoint": "0x00000000000000000000000000000000000000aa",
  "standardMempoolId": "QmcFZKUX9qoo3StwVycJTAhwdiqbEjcwNvQVK246p3z1rk",
  "supportedMempools": [
    {
      "mempoolId": "QmcFZKUX9qoo3StwVycJTAhwdiqbEjcwNvQVK246p3z1rk",
      "entryPoint": "0x00000000000000000000000000000000000000aa"
    }
  ],
  "relayers": ["0x{RELAYER_PRIVATE_KEY}"],
  "rpcEndpoint": "http://localhost:8545"
}

relayers and a few other fields can also be set with environment variables such as SKANDHA_RELAYERS, SKANDHA_BENEFICIARY and SKANDHA_RPC. See Configuration and CLI options.

How relaying works

In auto bundling mode the sidecar relays validated transactions on an interval through the PrivilegedRelayer. It calls ethrex_submitPrivilegedFrameTransaction on a co-located, trusted ethrex node. That method forces the transaction into the next payload build and bypasses ethrex’s own mempool. It is unauthenticated, so run it only against your own trusted node. The sidecar is an outsourced mempool client for one node, not a general-purpose bundler.

Enable the explorer API

Start with --explorer.enable to record admission reports and lifecycle events. See Reading admission reports.