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Hermes IBC relayer


Cosmos ecosystem

Build Status Integration tests Apache 2.0 Licensed Rust Stable Rust 1.76+

Rust implementation of an Inter-Blockchain Communication (IBC) relayer.

This project comprises primarily of 6 crates:

  • ibc-relayer provides an implementation of an IBC relayer, as a library.
  • ibc-relayer-cli is a CLI (a wrapper over the ibc-relayer library), comprising the hermes binary.
  • ibc-chain-registry provides functions to fetch data from the chain registry and automatically generate chain configuration for Hermes.
  • ibc-telemetry is a library for use in the Hermes CLI, for gathering telemetry data and exposing that in a Prometheus endpoint.
  • ibc-relayer-rest is a library for use in the Hermes CLI, for exposing a REST API to inspect the state of the relayer.
  • ibc-test-framework provides the infrastructure and framework for writing end-to-end (E2E) tests that include the spawning of the relayer together with Cosmos full nodes.

See the table below for more details.

⚠️ The ibc and ibc-proto crates have been moved to their own repositories.

The repository also includes TLA+ specifications.


Crate name Type Version Docs
ibc-relayer-cli bin: hermes IBC Relayer CLI Crate IBC Relayer CLI Docs
ibc-relayer lib IBC Relayer Crate IBC Relayer Docs
ibc-chain-registry lib Chain Registry Crate Chain Registry Docs
ibc-relayer-rest lib IBC Relayer REST Crate IBC Relayer REST Docs
ibc-telemetry lib IBC Telemetry Crate IBC Telemetry Docs
ibc-test-framework lib IBC Test Framework Crate IBC Test Framework Docs


The crates in this project require Rust 1.76.0.

Hermes Guide

We have a comprehensive guide at


IBC is specified in English in the cosmos/ibc repo. Any protocol changes or clarifications should be contributed there.

This repo contains the TLA+ specification and Rust implementation for the IBC modules and relayer. If you're interested in contributing, please comment on an issue or open a new one!

See also


We follow Semantic Versioning, though APIs are still under active development.



Copyright © 2023 Informal Systems Inc. and Hermes authors.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use the files in this repository except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.