Templating

Strøm uses Tera for templating. Templates are rendered when a worker claims a step (or server-side for task actions).

Available context

Inside a step’s input templates and when conditions, you have access to:

Variable	Description
input.*	Job-level input (from the API call or trigger)
<step_name>.output.*	Output from a completed upstream step
secret.*	Resolved workspace secrets

Basic usage

actions:
  greet:
    type: script
    script: "echo Hello {{ input.name }}"
    input:
      name: { type: string, required: true }

Passing data between steps

When a step emits structured output (via OUTPUT: {json}), downstream steps can reference it in templates.

actions:
  greet:
    type: script
    script: "echo Hello {{ input.name }} && echo 'OUTPUT: {\"greeting\": \"Hello {{ input.name }}\"}'"
    input:
      name: { type: string, required: true }

  shout:
    type: script
    script: "echo {{ input.message }} | tr '[:lower:]' '[:upper:]'"
    input:
      message: { type: string, required: true }

tasks:
  hello-world:
    mode: distributed
    input:
      name: { type: string, default: "World" }
    flow:
      say-hello:
        action: greet
        input:
          name: "{{ input.name }}"
      shout-it:
        action: shout
        depends_on: [say-hello]
        input:
          # say-hello -> say_hello (hyphens become underscores)
          message: "{{ say_hello.output.greeting }}"

Step name rules

Caution

Step names with hyphens (e.g., say-hello) are sanitized to underscores (say_hello) in the template context because Tera interprets hyphens as subtraction.

• Step names in YAML can use hyphens: say-hello
• In template references, use underscores: {{ say_hello.output.* }}

Tera features

Tera supports filters, conditionals, and more:

# Filters
script: "echo {{ name | upper }}"
script: "echo {{ name | default(value='World') }}"

# Conditionals
script: "{% if enabled %}echo Active{% else %}echo Inactive{% endif %}"

See the Tera documentation for the full feature set.

Input defaults with templates

Task input defaults support Tera templates with access to secret.*. Defaults are rendered at job creation time, before the job is persisted:

tasks:
  deploy:
    input:
      api_key:
        type: string
        default: "{{ secret.DEPLOY_KEY }}"

See Input & Output for full details on default values.

Secret references in templates

The | vals filter resolves secret references at template render time. See Secrets & Encryption for details.

env:
  DB_PASSWORD: "{{ 'ref+awsssm:///prod/db/password' | vals }}"

Conditional step execution

Steps support a when field for conditional execution. The condition is a Tera template that evaluates to true or false when the step’s dependencies are met:

tasks:
  conditional:
    input:
      run_checks: { type: boolean, default: false }
    flow:
      check:
        action: validate
        when: "{{ input.run_checks }}"

      process:
        action: process-data
        depends_on: [check]
        continue_on_failure: true
        # Runs whether check ran or was skipped

See Conditional Flow Steps for the full feature documentation.