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Hello, again

I codify contracts between systems for a living, in Rust and Python. I once spent five years chasing where the antimatter went.

Senior software engineer at PactFlow (SmartBear). I help lead the open-source Pact Foundation and maintainpact-python; I also wrote tikz-feynman,rust-skiplist, and more.

Previously: data and cloud engineering at KPMG, and doctoral research in theoretical particle physics.

The year in code

4785 commits, 744 PRs, and 274 issues across 37 repositories.

Oct 2025 — Oct 2026
Most of what I make is open. Each square below is one day of my GitHub contributions over the past year.

Latest commits

JP-Ellis/borrow-checkertest(e2e): pin the cold-start replay guards2d
JP-Ellis/borrow-checkerfix(ui): replay the last location only on a tab's first load2d
JP-Ellis/borrow-checkertest(e2e): cover the cold-start replay of the last location2d
JP-Ellis/borrow-checkertest(e2e): cover the display window kept in the URL2d
JP-Ellis/borrow-checkertest(core): check roll-ups and scoped streams against the leg oracle2d
JP-Ellis/borrow-checkertest(core): pin the residual default tier of account_totals to id order2d

Latest issues & PRs

cargo-lambda/cargo-lambda[PR · open]
fix: parse TOML 1.1 manifests20h
cargo-lambda/cargo-lambda-cdk[PR · open]
fix: parse TOML 1.1 manifests20h
JP-Ellis/borrow-checker[PR · open]
feat(ui): delete and reverse from the register detail2d
JP-Ellis/borrow-checker[PR · open]
feat(ipc,cli): delete, provenance and rejected-row commands2d

Selected projects

pact-pythonOSS · libraryPython bindings for Pact, rebuilt over a Rust FFI core. Downloaded over 1.3 million times a month.↗ github
tikz-feynmanOSS · LaTeXA LaTeX package for typesetting Feynman diagrams with TikZ; adopted across particle physics with 400+ academic citations.↗ github
rust-skiplistOSS · libraryA skip list for Rust.↗ github
↗ All projects