_anchors

You copy the same checkout + setup-node (+ cache) preamble into every job. It is not parameterized — it is literally the same steps — but Actions YAML gives you no way to name a step list and reuse it. _anchors: is a reserved top-level home for native YAML anchors: define a step list once with &name, drop it into any job with - *name, and Actio flattens it in place at compile time. The _anchors key is stripped from the output, so the generated workflow is byte-for-byte what you would have written by hand.

.actio.yml

name: CI
on: [push]
_anchors:
  setup: &setup
    - uses: actions/checkout@v4
    - uses: actions/setup-node@v4
      with:
        node-version: 20
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - *setup
      - run: npm test
  lint:
    runs-on: ubuntu-latest
    steps:
      - *setup
      - run: npm run lint

generated .yml

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 20
      - run: npm test
  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 20
      - run: npm run lint

.actio.yml

name: CI
on: [push]
_anchors:
  setup: &setup
    - uses: actions/checkout@v4
    - uses: actions/setup-node@v4
      with:
        node-version: 20
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - *setup
      - run: npm test
  lint:
    runs-on: ubuntu-latest
    steps:
      - *setup
      - run: npm run lint

generated .yml

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 20
      - run: npm test
  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 20
      - run: npm run lint

A - *alias whose anchor is a step list is spliced into the surrounding steps (recursive, with a depth cap); anchors that hold scalars or maps resolve as ordinary YAML. Anchors are pure YAML, so they need no Actio-specific syntax.

When to use _anchors vs templates vs fragments

You need	Use
Same step list, no parameters, same file	`_anchors:` — native, zero new syntax
The list varies by a value (version, target, name)	`templates` — typed `params:` + `inject … with`
The list lives in another file	`templates` — `inject: ./lib#name`
(legacy) named step blocks via `- inject:`	`fragments` — deprecated, migrate to the above

Reach for _anchors: first: it is the simplest reuse and adds no macro surface. The moment you need a parameter or a second file, switch to templates:.

See the canonical _anchors entry for the full keyword contract.

_anchors

When to use _anchors vs templates vs fragments

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