Exploring participants

Every step in a duckflux workflow is a participant — the atomic unit of work. Participants receive input, do something, and produce output. The flow is just an ordered sequence of participants.

There are two dimensions to understand: how you define a participant (anonymous, named inline, or reusable) and what type it is (exec, http, mcp, workflow, emit).

Definition modes

Anonymous inline

The simplest form. Write the participant directly in the flow without a name:

flow:
  - type: exec
    run: curl -s https://api.example.com/data

  - type: exec
    run: ./process.sh

Each step’s output is automatically passed to the next step — like Unix pipes. Anonymous participants are quick to write, but their output can’t be referenced by name in later steps.

Named inline

Add as to give a step an addressable name, while still defining it inline:

flow:
  - as: build
    type: exec
    run: npm run build

  - as: deploy
    type: exec
    run: ./deploy.sh
    input: build.output.artifactPath

Named steps are addressable in CEL expressions (build.output, build.status, etc.). Use this when you need to reference the result downstream, but the step is only used once.

Reusable participants

Define steps in the top-level participants block and reference them by name in the flow. This is ideal for steps that appear more than once, or have complex configuration:

participants:
  test:
    type: exec
    run: npm test
    timeout: 5m
    onError: retry
    retry:
      max: 2
      backoff: 5s

flow:
  - test
  - deploy
  - test           # run again after deploy

Reusable participants keep the flow readable and the configuration in one place.

Comparing the three modes

	Anonymous	Named inline	Reusable
Defined in	`flow` (no `as`)	`flow` (with `as`)	`participants` block
Output addressable by name	❌ No	✅ Yes	✅ Yes
Can appear multiple times	❌ No	❌ No	✅ Yes
Best for	Simple one-off steps	One-off named steps	Shared steps, complex config

Participant types

The type field determines how a participant executes:

exec Runs a shell command. Output is the command's stdout.

http Makes an HTTP request. Supports dynamic URLs, headers, and body via CEL.

mcp Invokes a tool on an MCP server.

workflow Runs another .duck.yaml file as a sub-workflow.

emit Publishes an event to the workflow's event hub.