Use when writing, changing, fixing, debugging or refactoring code in any language, including a one-line fix, a config value, or a shell snippet embedded in another file. Covers .nix, .rs, .py, .ts, .tsx, .js, .sh, .go, .cs and their config files, including .NET Framework and .NET Core/5+. Carries the conventions that apply everywhere (naming, comments, error handling, scope, matching the surrounding code) and routes to per-language guidance for Rust, Python, Nix, TypeScript/JavaScript, shell, Go and C#/.NET, plus assertions and crash-early behaviour, thread-safety and shared state, input validation and secrets, observability (logging, tracing, structured log fields, correlation IDs, instrumenting new code so behaviour can be read from its output instead of guessed at), and performance work — profiling, benchmarking, and SIMD/vectorization.
Use when reviewing a diff, a pull request, or your own work before committing or handing it over, including "look over this change", "is this right", or checking for bugs you introduced. Also use when auditing an existing codebase or module against current conventions — "review this codebase", "does this project follow our standards", "check this against the programming skill" — with no diff to anchor against. Carries the rubric for judging code (including conformance with the `programming` skill's language and by-concern guidance), severity ordering, how to phrase a finding so it is actionable, and how to verify a finding is real before reporting it.
Use when committing, amending, splitting or reordering changes, opening / updating / reviewing / merging a pull request, choosing a merge strategy, branching, or setting up an isolated worktree, including "commit this", "push it", "open a PR". Also when review lands on your own PR: watching or waiting for a review, answering review comments, replying to or resolving review threads, addressing requested changes from a human or a bot, requesting Copilot re-review, or enabling auto-merge / `gh pr merge --auto`. Also for running the whole commit-branch-PR-review-merge sequence unattended: "ship this", "commit, open a PR, and merge it once it's reviewed". Carries the atomic-commit and never-squash mandate, the commit message format, and routes to commit, PR, review-response, auto-ship and worktree guidance.
