atmos-modernization

DevOps & Security

Atmos Modernization: migrate deprecated or legacy Atmos patterns to current names, Native CI, Atmos Pro drift detection, dependencies.components, name_template, and declared secrets

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Source SKILL.md: https://github.com/cloudposse/atmos/blob/HEAD/agent-skills/skills/atmos-modernization/SKILL.md

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Atmos Modernization

Use this skill when updating older Atmos projects to current conventions. "Atmos Modernization" is the umbrella term for replacing legacy patterns with supported, current patterns.

Modernization Checklist

Legacy pattern	Replace with
`name_pattern`	`name_template` or explicit stack `name`
`settings.depends_on`	`dependencies.components`
`cloudposse/github-action-atmos*` wrapper actions	Native CI with direct `atmos` commands
`cloudposse/github-action-setup-atmos` as default	GitHub Actions container `ghcr.io/cloudposse/atmos:<version>`
`hashicorp/setup-terraform` / `opentofu/setup-opentofu` in Atmos jobs	Atmos `dependencies.tools` and toolchain
Manual `atmos toolchain install <tool>` preinstall steps for Atmos-owned tools	Declarative `dependencies.tools` at the owning component, workflow, hook, or custom command
Large inline workflow/custom-command shell scripts, repeated `echo`, shell loops, ad hoc sleeps	Native step types such as `atmos`, `toast`, `table`, `parallel`, `matrix`, `wait`, `container`, `emulator`, and `http`
Hand-rolled scheduled drift GitHub Actions	Atmos Pro drift detection
`cloudposse/github-action-atmos-terraform-drift-*`	`settings.pro.drift_detection` plus `atmos terraform plan --upload-status`
Secret values through raw store calls	Declared `secrets.vars` plus `!secret`
Legacy hook event spelling	Modern dotted lifecycle events such as `after.terraform.plan`
Static GitHub tokens in URLs	Atmos Auth `github/sts` through Atmos Pro
`cloudposse/terraform-aws-components` sources	Repos in the `cloudposse-terraform-components` organization

Process

Inspect current project behavior with atmos describe stacks, atmos list components, and atmos validate stacks.
Replace one class of legacy pattern at a time.
Preserve resolved stack output unless the modernization intentionally changes behavior.
Validate with atmos describe component <component> -s <stack> before changing CI.
Update CI last, after stack config and auth patterns are current.

Native CI Direction

New CI should run Atmos directly, preferably in the Atmos container image:

jobs:
  plan:
    runs-on: ubuntu-latest
    container:
      image: ghcr.io/cloudposse/atmos:${{ vars.ATMOS_VERSION }}
    permissions:
      contents: read
      id-token: write
    steps:
      - uses: actions/checkout@v6
      - run: atmos terraform plan vpc -s prod

Use atmos describe affected --format=matrix for PR matrices and atmos list instances --format=matrix for full estate operations.

Drift Direction

Atmos Pro is the product path for drift detection. Enable drift per stack/component:

settings:
  pro:
    enabled: true
    drift_detection:
      enabled: true

Then upload plan status:

atmos terraform plan vpc -s prod --upload-status

Dependencies Direction

Use dependencies.components for component, file, and folder dependencies:

dependencies:
  components:
    - component: vpc
    - component: dns-zone
      stack: plat-ue2-prod
    - kind: file
      path: configs/service.yaml
    - kind: folder
      path: src/lambda

Treat settings.depends_on as migration-only syntax.

Component Source Repository Direction

Check source, vendor.yaml, component.yaml, Terraform module sources, and documentation examples for cloudposse/terraform-aws-components. That monorepo is deprecated; components moved to individual repositories in the cloudposse-terraform-components organization.

For example, migrate VPC references from the old monorepo form:

source: "github.com/cloudposse/terraform-aws-components.git//modules/vpc?ref=1.450.0"

to the component repository form:

source: "github.com/cloudposse-terraform-components/aws-vpc.git?ref=1.450.0"

Keep versions pinned when changing sources, and validate the target repository/tag exists before updating production stacks.