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Informal Systems is a company focused on building trusted software and monetary systems, with core businesses in formal verification, protocol design, security auditing, and distributed systems development. Its representative tools include the Quint modeling language, the Apalache symbolic model checker, the Modelator test generation tool, and cosmwasm-to-quint, which are used to improve system correctness and automatically generate tests. The company is deeply involved in the Cosmos ecosystem, developing infrastructure related to the IBC interoperability protocol and the Tendermint consensus engine, as well as operating validator services.
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About Informal Systems
Informal Systems is a core software developer for the Cosmos network, focusing on the Tendermint consensus engine and the IBC cross-chain communication protocol, with an emphasis on formal verification. Its main business includes: providing highly secure consensus mechanisms for blockchain networks, developing cross-chain interoperability standards, and operating validator nodes (e.g., Informal Staking) to support network decentralization.
The market pain point is that blockchains lack unified, secure communication protocols; consensus algorithms are vulnerable to attacks and difficult to formally verify, leading to trust risks in cross-chain asset transfers and ecosystem collaboration. Informal Systems addresses this by using formal methods (e.g., TLA+ specifications) to verify critical protocols and by promoting IBC as an industry standard, solving interoperability and security challenges.
In the past six months (March to September 2026), the company has continued advancing partnerships with Layer 2 networks like Starknet, integrating IBC into non-Cosmos ecosystems to expand cross-chain coverage. Meanwhile, its validator node services remain active, and it participates in consensus security audits across multiple blockchain networks. Overall, recent development focuses on broadening IBC use cases and strengthening protocol formal guarantees.
Informal Systems was founded in early 2020 by Ethan Buchman, Zarko Milosevic, Josef Widder, among others, originating from the Interchain Foundation to provide rigorous protocol engineering for the Cosmos network. Its first major project was the Rust implementation of the IBC protocol and a TLA+ formal specification; model checking results led to protocol improvements, and the Hermes relayer was developed and deployed in production after the IBC launch in 2021. The team also formally verified the Tendermint light client and maintained its Rust implementation. In summer 2022, Informal took over maintenance of Tendermint Core (Go), restoring trust after the withdrawal of v0.35/v0.36, advancing ABCI 2.0, and releasing v0.37/v0.38. Its Apalache symbolic model checker was used in security audits and specification verification of several core protocols, including Tendermint consensus, light client, and fast sync. In 2023, Informal helped the Cosmos Hub ship V8 and V9, with V9 introducing Replicated Security, laying the foundation for shared security across chains. These efforts established the formal methods and infrastructure cornerstone of the Cosmos ecosystem.
Informal Systems was co-founded by Ethan Buchman, Arianne Flemming, and Zarko Milosevic.
Ethan Buchman (CEO) is a co-founder of Cosmos and Tendermint, former Technical Director at the Interchain Foundation, and holds a master's degree from the University of Guelph. He also leads Cycles Protocol.
Arianne Flemming (COO) graduated from Princeton University, founded multiple companies, and served as Associate Director of Machine Learning at the Creative Destruction Lab.
Zarko Milosevic (CTO) holds a PhD in distributed systems from EPFL, specializing in consensus protocols and formal verification.