firefox

Steps to reliably split a commit/change using the jj (jujutsu) VCS

Analyze a range of local commits, and reorganize them to minimize latency and friction in the review and landing process. To achieve this, commits can be split, reordered, squashed / grouped, or even rewritten. In the final commit series / "patch stack", the codebase should build, lint, and test cleanly after every commit, and each individual commit should stand on its own.

Structured performance opportunity investigation for SpiderMonkey (the Firefox JavaScript engine). Use this skill when the user wants to investigate JS engine performance, profile SpiderMonkey, find optimization opportunities, write performance patches, or evaluate benchmark regressions. Trigger on mentions of: profiling JS, SpiderMonkey performance, JIT optimization, benchmark regression analysis, shell benchmarking, or any request to make JS workloads faster. The methodolgy is described mostly for the JS shell but can be adapted to browser investigation.

Analyze Firefox performance profiles using the profiler-cli CLI tool. Trigger when given a profiler.firefox.com or share.firefox.dev link, a local profile path, or when the user wants to investigate an issue in a Firefox profile. Always use this skill instead of WebFetch for Firefox profiler URLs; WebFetch only retrieves the profiler UI's HTML shell and cannot access profile data, whereas profiler-cli downloads and parses the actual profile into a local daemon that supports structured queries over stacks, markers, threads, and samples.

Guide for creating new Android gradle modules in the android-components project.

Use webspec-index to query WHATWG, W3C, IETF and TC39 web specifications from the command line

Map relationships between a web spec section, its Firefox implementation code, and Web Platform Tests. Use when starting work on a spec feature, checking implementation coverage, or finding which WPTs to enable.

Workflow guide when working with Android builds or the mobile/ directory.