#Inheritance and overrides

Two mechanisms share one rule: a name means one command across the repository, and inheriting can only add to it.

#extends

An extends script resolves another script's command and appends its own arguments.

export default defineConfig({
  scripts: {
    test: { command: 'vitest run --reporter=dot' },
    'test:coverage': { extends: 'test', appendArgs: ['--coverage'] },
    'test:ci': { extends: 'test:coverage', appendArgs: ['--reporter=junit'] },
  },
});

test:ci resolves to:

vitest run --reporter=dot --coverage --reporter=junit

Chains resolve transitively, in declaration order from the base outward. A cycle is rejected with the names that form it.

appendArgs entries are quoted per element for the shell that will run the command, the same way arguments after -- are. An entry containing a space arrives as one argument.

appendArgs without extends is a type error, and Rune rejects it as an unknown field.

#Package overrides

A package may hold its own rune.config.ts. Rune uses the nearest one it finds, so a script name defined in both resolves to the package's version.

export default defineConfig({
  scripts: {
    test: { extends: 'test', appendArgs: ['--maxWorkers=1'] },
  },
});

Inside packages/legacy, rune run test runs the root command plus --maxWorkers=1. Everywhere else it runs the root command. Neither package.json changed.

#Extend, never replace

A package config that gives a colliding name its own command is a validation error:

error: packages/legacy/rune.config.ts is not a valid rune config

script `test` also exists at the repository root.
an override may extend a script, not replace it.

either write `extends: 'test'`, or give this script a different name.

The reason is what the tool is for. A test that means one command in nine packages and something unrelated in the tenth reproduces the situation Rune removes, and it does it invisibly.

A name that does not exist at the root is not an override. It is a new script, scoped to that package.

#Ignoring the override

--root resolves against the root config only.

rune run test --root

#Seeing the chain

rune inspect prints the resolution, and it never spawns anything.

$ rune inspect test
  script      test
  defined     rune.config.ts:12                    root
  overridden  packages/legacy/rune.config.ts:4     + --maxWorkers=1
  command     vitest run --reporter=dot --maxWorkers=1
  cwd         /repo/packages/legacy

rune list annotates the same information more briefly: (defined here) for a script this package owns, (overridden here) for one it sharpens.

#The cache and two configs

The resolved config is cached by content. When a package override is in play, both configs and everything they import enter the cache key, so editing either one invalidates the entry. See Config evaluation.