atmos-modernization

name	atmos-modernization
description	Atmos Modernization: migrate deprecated or legacy Atmos patterns to current names, Native CI, Atmos Pro drift detection, dependencies.components, name_template, and declared secrets
metadata	{"copyright":"Copyright Cloud Posse, LLC 2026","version":"1.0.0"}

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
Parser-specific doubled double quotes ("") in !terraform.state or !terraform.output expressions	Direct YQ expressions; quote only as required by YAML

Process

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

YAML Function Quoting

Older stack manifests may wrap an entire YQ expression in double quotes and double its inner double quotes. That parser-specific escaping is obsolete: !terraform.state and !terraform.output parse the component, optional stack, and remaining expression directly.

Replace legacy string-default quoting:

# Before
username: !terraform.output config ".username // ""default-user"""

# After
username: !terraform.output config .username // "default-user"

Replace legacy string-concatenation quoting:

# Before
postgres_url: !terraform.state aurora-postgres ".master_hostname | ""jdbc:postgresql://"" + . + "":5432/events"""

# After
postgres_url: !terraform.state 'aurora-postgres .master_hostname | "jdbc:postgresql://" + . + ":5432/events"'

The outer single quotes in the concatenation example are YAML quoting, not function-parser escaping. Use YAML quoting only when the scalar requires it; for complete YAML and YQ quoting guidance, see the atmos-yaml-functions skill.

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.