Just Command Runner Skill

Just Command Runner

Create readable task automation that matches the repository's installed Just version and existing justfile conventions.

Defaults

Inspect just --version, the existing justfile/module tree, and just --list before editing. Installed capabilities and existing syntax are authoritative over this skill's examples.
Preserve bespoke formatting. Do not rewrite a justfile with just --fmt; use just --fmt --check only when the repository explicitly treats the built-in formatter as authoritative. just --dump is inspection output, not a formatting source.
Define multi-item string sequences one item per line with a parenthesized concatenation. Keep a trailing separator in every non-final item; do not collapse them into one long string. Triple-quoted strings are for values whose newlines are semantic, not visual wrapping. For example:
```
check-steps := (
  "event-class-coverage " +
  "orphan-disposal " +
  "price-coverage"
)
```
Prefer explicit, small recipes; Just-native executable checks; private helpers; check/write recipe pairs; and aliases after their target recipes. Prefer which() plus assert() with actionable install guidance over shell command -v or backtick which checks when the justfile already enables set unstable and set lists. Otherwise, use require() when its generic missing-executable error is sufficient. Put an assertion at top level only when every recipe needs that tool; otherwise make it a private prerequisite of the affected recipes.
Make recipes quiet by default: prefix the recipe name with @ unless echoing commands has clear value. Recipe-level @ inverts per-line @, so never also prefix lines inside a @recipe. Never add @ to a [script] recipe: scripts are already quiet, and @ un-mutes them. See "Quiet Recipes and Command Prefixes" in references/recipes.md.
On stock macOS, assume /bin/bash 3.2 unless the recipe explicitly selects a newer shell.
Use the user's section-banner style when creating a new standalone justfile; existing repository organization overrides it.

Workflow

Determine the requested recipe behavior, inputs, outputs, cwd, shell, environment, dependencies, and success condition.
Use the installed manual (just --help, just --man, or https://just.systems/man/en/) for version-sensitive syntax. Read only the task-specific reference:

| Task | Reference | | ------------------------------------------ | ------------------------------ | | Recipes, parameters, dependencies, cache | references/recipes.md | | Settings, dotenv, lists, modules | references/settings.md | | Expressions, functions, constants | references/syntax.md | | Shell or script recipes | references/inline-scripts.md | | Check/write, status, aliases, organization | references/patterns.md |
Make the smallest recipe or setting change. Do not enable unstable features unless the requested design needs them and the installed version supports them.
Validate parsing with just --list or just --summary, then execute the narrowest safe recipe path. For state-changing recipes, use an existing dry-run/check mode or inspect the expanded command first.

Opinionated Organization

For a new standalone file, prefer dependency declarations, constants, public recipes, checks, then private helpers. Use set default-list := true when no single default action makes sense and the installed version supports it. Example starting points live in examples/standalone.just and examples/devkit.just; load one only when creating that shape.

Completion requires a parsable justfile, the requested recipe behavior, and execution or dry-run evidence appropriate to its side effects. Finish with ### ✅ Just workflow ready, a compact recipe/alias/purpose table when several entries changed, and ### 🧪 Verification with exact commands and outcomes. Keep confirmation prompts, recipe data output, compiler output, and just --list output undecorated; preserve the repository's own banner vocabulary.

Agent Skills: Just Command Runner

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Skill Files