Contract Software Engineer - DOM Core Firefox/Gecko

Role overview A contract software engineer is needed to reinforce the DOM Core area of a major open-source web browser project, with a specific focus on improving the health of the Session History subsystem. Day-to-day work combines authoring automated tests with diagnosing and fixing correctness issues so that the engine becomes more reliable for users and downstream consumers. Successful execution unblocks senior engineers to focus on security, performance, and long-horizon strategic projects.

Responsibilities - Design and write Web Platform Tests that expand coverage of Session History behavior, plus engine-specific mochitests where needed - Investigate failing tests and root-cause the underlying correctness problems, then ship fixes that pass cleanly - Drive changes through public code review with relevant module owners and iterate until they land upstream - Maintain existing test suites and harness code so future regressions surface earlier - Measure progress against a clear definition of done based on passing test counts and reduced defect rate

Requirements - Substantial prior experience working inside a browser-engine codebase or building automation for one, ideally the same engine - Strong JavaScript fluency applied to writing automated tests - Working proficiency in C++ for navigating and modifying engine internals - Solid debugging skills across a large, mature codebase - Comfort operating in the open: public bug trackers, public review, and upstream contribution norms

Nice to have - Prior merged contributions to a major browser engine - Familiarity with web standards work and the Web Platform Tests ecosystem