hermes

IBC relayer between chain instances

Instance.hermes() wraps the Hermes IBC relayer. Give it running chain instances and a funded relayer account, and it writes the Hermes config, registers keys, creates clients/connections/channels, and starts relaying — start() resolves once every requested channel is open.

Install the binary

Grab a release from informalsystems/hermes and put hermes on PATH.

Usage

import { Instance, testAccounts } from 'starskiff';
 
const relayerMnemonic = testAccounts[1].mnemonic; // must be funded on ALL chains
 
const chainA = Instance.wasmd({
  chainId: 'ibc-a',
  prefix: 'wasm',
  accounts: [{ mnemonic: relayerMnemonic, coins: '1000000000stake', name: 'relayer' }],
});
const chainB = Instance.wasmd({
  chainId: 'ibc-b',
  prefix: 'wasm',
  rpcPort: 26757, // distinct ports — see the multi-chain guide
  // ...
  accounts: [{ mnemonic: relayerMnemonic, coins: '1000000000stake', name: 'relayer' }],
});
 
await Promise.all([chainA.start(), chainB.start()]);
 
const relayer = Instance.hermes(
  {
    channels: [[chainA, chainB]], // one [chain, chain] tuple per channel
    mnemonic: relayerMnemonic,
  },
  { timeout: 180_000 }, // handshakes take a while
);
await relayer.start(); // resolves when channel-0 is open

Channels are created in order: the first tuple becomes channel-0 (on both ends of that pair), the next channel-1, and so on.

EVM chains as counterparties

Instances built on cosmosEvmBase (e.g. evmd) advertise relayerHints — Hermes needs to know they use ethermint address derivation (coin type 60) and which protobuf PubKey type to use. Instance.hermes() picks the hints up automatically; mixed pairs like [wasmd, evmd] just work.

Parameters

Parameter	Type	Default	Description
`channels`	`[CosmosInstance, CosmosInstance][]`	— (required)	Channel pairs to create + relay
`mnemonic`	`string`	— (required)	Relayer account, funded on all chains
`binary`	`string`	`"hermes"`	Path to the binary
`gasPrice`	`string`	`"0.025"`	Gas price amount
`telemetryPort`	`number`	`3001`	Telemetry port
`debug`	`boolean`	`false`	Verbose setup logs
`commandTimeoutMs`	`number`	`300000` (`600000` in CI)	Timeout per Hermes command
`commandRetries`	`number`	`0` (`2` in CI)	Retries for setup commands
`commandRetryDelayMs`	`number`	`5000`	Delay between retries

See the IBC guide for an end-to-end transfer test.