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Interoperability & Bridges

Union

Union is a public Rust-based, Apache-2.0 interoperability protocol and infrastructure layer for zero-knowledge cross-chain message passing, asset transfers, NFTs and DeFi.

Explore the practical guide ↓

Independent OpenViST project profile, based on linked sources.

Union — OpenViST project profile in Interoperability & Bridges.
OpenViST project illustration. See the linked sources for product details.
Understand the project

Practical overview

When it fits

Use Union when a project needs a documented interoperability layer for cross-chain messages or transfers across supported Cosmos and EVM environments, and when a zero-knowledge, consensus-verification architecture is relevant to the design.

Who it is for

  • Developers building cross-chain applications
  • Teams working with Cosmos or EVM ecosystems
  • Operators and contributors evaluating or extending interoperability infrastructure
  • Builders of asset, NFT and DeFi workflows spanning compatible chains

Documented uses

  • Send general messages between supported blockchain ecosystems
  • Transfer assets across chains
  • Transfer NFTs across chains
  • Create DeFi workflows using cross-chain messages or asset transfers
  • Build or operate protocol infrastructure using IBC-compatible components
Before you choose

Requirements & limits

The project is publicly available as an Apache-2.0 repository.

  • The protocol implements IBC for Cosmos compatibility.
  • The repository documents connections to EVM networks and publishes a supported-chain list.
  • The design states that it does not depend on trusted third parties, oracles, multisignatures or MPC; this claim was not independently assessed in the supplied material.
  • The repository includes multiple components and languages, so implementation choices may depend on whether a project needs a node, prover, relayer, contract stack or SDK.
  • The documented Nix setup supports reproducible builds, while some components require Linux.

Check current requirements in the official documentation. Source-based guidance does not mean OpenViST has run or independently tested this project.

Source-based practical guide

Set up a reproducible Union development environment

Install Nix, enter Union’s development shell and build documented repository components.

Before you start

  • A checkout of the Union repository
  • Nix
  • Linux for components that require it; the README notes macOS users can use an OrbStack-hosted NixOS VM

Steps

  1. Install Nix using the installation command documented in the repository README.

  2. From the repository, run nix build .#uniond -L, nix build .#voyager -L or nix build .#app -L.

  3. Inspect available packages with nix flake show if needed.

  4. Run nix develop to enter the development shell with the documented dependencies.

  5. Run nix run .#pre-commit -L to format the repository and check spelling before a pull request.

Expected outcome

The selected component is built into `result/`, and the development shell provides the repository’s documented tool dependencies.

Guide limitations

  • Some components can only be built on Linux.
  • The documented commands describe local building and development setup, not deployment or protocol integration.
  • The supplied material does not document build results beyond the stated output location.
Documentation 1 ↗
Evidence and transparency

Sources & review

Official repository ↗
Source record details
Source availability
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Sources checked
1 October 2026
Original website title
unionlabs/union · Official homepage title · retained in its source language
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