xxviii · ix · mmxxvi

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

4377 commits, 674 PRs, and 231 issues across 34 repositories.

Sep 2025 — Sep 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): cover a sign-flip save and its formula14h
JP-Ellis/borrow-checkerdocs: show budget revisions in the §7.1 schema15h
JP-Ellis/borrow-checkerfeat(bc-ui): accept expressions in the new budget form15h
JP-Ellis/borrow-checkertest(bc-ui): reach the tag check in account_and_tag15h
JP-Ellis/borrow-checkerrefactor(bc-ui): share budget form dropdown keys15h
JP-Ellis/borrow-checkerfix(bc-core): no verdict on future over-allocation15h

Latest issues & PRs

JP-Ellis/borrow-checker[PR · open]
docs(gui): correct three specs the budget work outdated12h
JP-Ellis/borrow-checker[issue · open]
Stale bc.sidebar.expanded collapses the sidebar in accounts-* e2e specs12h
JP-Ellis/borrow-checker[issue · open]
Budget tree shows no unbudgeted spend under Asset/Liability roots12h
JP-Ellis/borrow-checker[issue · open]
Budget envelopes: consider an exclusive (residual) counting mode12h

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