Union

• Name: Union
• URL: https://union.build/
• Category: Interoperability protocol / zero-knowledge bridging / chain-abstraction infrastructure
• Summary: Union is a proof-heavy interoperability stack built around consensus verification, ZK proving, and IBC-style message passing across heterogeneous chains. The key point is not chain abstraction branding. It is an attempt to replace committee-trust bridge design with a proving and verification stack that still has real operator edges.
• What it does:
  • Provides interoperability infrastructure for general message passing, asset transfers, NFTs, DeFi workflows, and application-specific cross-chain intents
  • Uses consensus verification and zero-knowledge proving to verify counterparty-chain messages instead of depending on custodial multisigs, oracles, or MPC committees
  • Extends IBC-style connectivity beyond Cosmos to EVMs, SVMs, and other execution environments, while marketing itself as chain-abstraction and aggregation infrastructure
  • Ships a broad open-source stack including the Union node (uniond), prover (galoisd), relayer (voyager), light clients, smart contracts, and production supervisor tooling
  • Publishes docs, research surfaces, status pages, ecosystem materials, and an official whitepaper PDF
• Key claims:
  • The homepage calls Union the next generation of aggregation, interoperability, and chain abstraction, and describes it as the first subsecond messaging protocol for application-specific intents and transfers
  • Official docs describe Union as a hyper-efficient zero-knowledge infrastructure layer for general message passing, asset transfers, NFTs, and DeFi with no dependencies on trusted third parties, oracles, multisigs, or MPC
  • The consensus-verification docs frame Union’s core differentiation as proving counterparty-chain truth cryptographically rather than trusting external keepers or signer sets
  • The CometBLS architecture docs explain that aggregated BLS signatures are meant to reduce verification costs, improve proving efficiency, and support hundreds to thousands of validators over time
  • The public repository shows Union is shipping much more than a bridge frontend: nodes, provers, relayers, CosmWasm contracts, light clients, and production node-supervision tooling are all part of the official stack
• Whitepaper: Official whitepaper exists and is saved locally as ../whitepapers/union-whitepaper.pdf. The most useful directly inspected primary materials in this pass were the homepage, docs overview, consensus-verification docs, CometBLS docs, and public GitHub repository; see ../whitepapers/union-primary-sources-2026-04-25.md.
• Sources:
  • https://union.build/
  • https://docs.union.build/
  • https://docs.union.build/concepts/consensus-verification
  • https://docs.union.build/architecture/cometbls
  • https://github.com/unionlabs/union
  • https://drive.google.com/file/d/11BawNxXch9xX8aRJl0ZqDAb925NjDuHH/view

Internal linkages

• Best upward reads: hyperbridge, snowbridge, and hyperlane.

Control surface

• Practical authority sits in chain admission, prover and relayer operation, validator assumptions, supported execution environments, and upgrade or emergency-response rights.

• Zero-knowledge narrows some trust assumptions, but it does not remove the operating stack that decides which cross-chain truths become usable in practice.

• Read Union as verification-first interoperability infrastructure, not as trustless magic.

• Last reviewed: 2026-05-25 UTC