Nikos Baxevanis
I’m a programmer and security researcher at the Ethereum Foundation, helping protect Ethereum mainnet and secure upcoming hard forks.
My background is in open source, functional programming, and property-based testing. Previously, I built fuzzing and model-based testing tools at the Stacks Foundation.
Projects
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2026 – present
Created mas — Coding agents running in Docker and coordinating through Git, without a central orchestrator or message passing. Supports Claude Code, Codex, and Pi. -
2022 – 2025
Created rendezvous and madhouse-rs, fuzzing tools for Clarity and Rust. Helped identify issues during network upgrade testing and chain behavior under load. -
2016 – present
Core contributor to Hedgehog — property-based testing for Haskell, F#, R, and Scala. Used in the early development of Echidna by Trail of Bits. -
2017 – 2020
Ported SplitMix — a fast splittable PRNG. Based on work by Steele, Lea, and Flood. Passes all dieharder tests. Used in Hedgehog for replay and shrinking. -
2011 – 2020
Ported dk.brics.automaton and xeger to create Fare — a library for generating regex-constrained strings. Used in AutoFixture. -
2011 – 2016
Core contributor to AutoFixture, a .NET testing library. Helped shape AutoFixture 3, contributed features and tools like Fare. Project later submitted to the .NET Foundation.
Writing
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2026-01-31 – The Bugs Between Calls
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2026-01-25 – Oracles, Traces, Triage
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2024-12-01 – Model-Based Stateful Testing with madhouse-rs
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2023-10-15 – Fuzzing in Memory-Safe Languages
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2023-02-17 – Input Coverage > Code Coverage
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2023-01-30 – Invariant testing from command-line
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2022-03-15 – Clarity model-based testing primer
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2022-03-05 – Clarity property-based testing primer
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2020-03-30 – The rhyme of the altered parser
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2017-04-10 – Less fragmented properties with Hedgehog
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2016-02-08 – Write you some QuickCheck
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2012-07-31 – AutoFixture, xUnit.net, and Auto Mocking