Atmos Compositions

Use this skill for compositions: named groupings of component instances that form a system. Compositions define the service contract; components fulfill services by referencing the composition.

Related Skills

Need	Load
Container components that fulfill services	atmos-container
Stack manifest structure	atmos-stacks
Workflow orchestration across services	atmos-workflows

Configuration

Declare composition service contracts at stack scope:

compositions:
  app:
    description: Application runtime
    services:
      - api
      - worker
      - db

components:
  container:
    api:
      composition: app
    worker:
      composition: app

The composition describes expected services. Components declare which composition they fulfill.

Validation

Use atmos composition validate to inspect whether a stack provides all services for a composition.

atmos composition validate app -s plat-ue2-dev

Validation reports fulfilled and not-provided services. Use this before running workflows that assume a complete multi-service system.

Guidance

• Use compositions for systems made of multiple stack-scoped services.
• Keep service names stable and human-readable.
• Do not use composition names as a replacement for Atmos profiles or ATMOS_PROFILE.
• Put shared composition definitions in stack mixins/defaults when multiple stacks use the same service contract.
• Prefer composition validation over hand-written checks in shell steps.