Open Source Contributions: Index

May through August 2025, I worked on Professor David Liu’s open-source team at UofT. Two codebases: MarkUs (Rails auto-grading platform used by every CS course at UofT) and PythonTA (static analysis tool built on top of Pylint, used by thousands of students).

These were my first real engineering jobs — the first time working inside a codebase someone else had been maintaining for a decade, with code review by staff, real users, and uptime that mattered. PythonTA was the on-ramp: AST manipulation, testing, the full PR lifecycle. MarkUs was the deeper one: a large Rails monolith with a real database, real authorization model, and real concurrency.

The patches that follow are the ones worth talking about. There were others — Rack deprecation migrations, touch-event handling for tablet grading, a few smaller fixes — that I’ve left off because they don’t carry the weight of these.

Index

• MarkUs. Rails work on UofT's auto-grading platform: an N+1 query that was costing every TA two seconds per page, scheduled-visibility windows shipped end-to-end, and model-layer invariants that let me delete a class of controller bugs.
• PythonTA. Static analysis tool for Python, built on Pylint and used by thousands of UofT students. AST manipulation, custom linter checks, and the HTML reporter that students see for every assignment.