Context assignment (set)

The set construct writes values into execution.context, a shared scratchpad that persists across the entire workflow run. Use it to assign intermediate values, derive configuration, or pass computed data between steps without piping through participants.

---

The set construct

A set block maps one or more keys to CEL expressions. Each evaluated result is stored as execution.context.<key>:

flow:
  - set:
      token: workflow.inputs.api_token
      region: "'us-east-1'"

  - as: fetch
    type: http
    url: "'https://api.example.com/data'"
    headers:
      Authorization: "'Bearer ' + execution.context.token"
      X-Region: execution.context.region

Tip

set is a flow-level control operation, like if or wait. It is not a participant — it has no type, produces no output, and does not affect the implicit I/O chain. The chain passes through it unchanged.

Fields

Each key inside the set block is a context variable name. The value is a CEL expression.

- set:
    <key>: <CEL expression>
    <key>: <CEL expression>

Aspect	Details
Keys	Any valid identifier, except reserved names (workflow, execution, input, output, env, loop, event).
Values	CEL expressions evaluated at runtime against the current state.
Multiple keys	Yes — assign as many as needed in a single set block.
Overwrite	If a key already exists in execution.context, it is overwritten.

---

Basic usage

Assign a literal string and a computed value:

flow:
  - set:
      env_name: "'production'"
      start_ts: "now"

  - as: deploy
    type: exec
    run: ./deploy.sh
    input:
      environment: execution.context.env_name

---

Using workflow inputs

Store values derived from workflow inputs for later reuse:

inputs:
  notion_token:
    type: string
  repo_url:
    type: string
    format: uri

flow:
  - set:
      token: workflow.inputs.notion_token
      repo: workflow.inputs.repo_url

  - as: fetch_pages
    type: http
    url: "'https://api.notion.com/v1/pages'"
    headers:
      Authorization: "'Bearer ' + execution.context.token"

---

Conditional assignment

Combine set with if to assign values based on conditions:

flow:
  - if:
      condition: has(workflow.inputs.custom_token)
      then:
        - set:
            api_token: workflow.inputs.custom_token
      else:
        - set:
            api_token: env.DEFAULT_API_TOKEN

  - as: call_api
    type: http
    url: "'https://api.example.com/action'"
    headers:
      Authorization: "'Bearer ' + execution.context.api_token"

---

Accumulating state across loop iterations

set is useful for building up state across loop iterations — for example, tracking a score that determines when to exit:

flow:
  - set:
      best_score: "0"

  - loop:
      until: execution.context.best_score >= 8
      max: 5
      steps:
        - reviewer
        - set:
            best_score: reviewer.output.score

  - as: report
    type: exec
    run: echo "Final score"
    input: execution.context.best_score

Caution

Step outputs inside a loop are overwritten on each iteration. If you need to preserve a value across iterations, use set to write it to execution.context.

---

Chain passthrough

set is transparent to the implicit I/O chain. The output of the step before set is passed unchanged to the step after it:

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

  - set:
      fetched_at: "now"

  - as: process
    type: exec
    run: ./process.sh    # receives fetch's output via chain, not set's

---

Complete example

id: context-pipeline
name: Context Assignment Pipeline
version: "1"

inputs:
  api_token:
    type: string
    required: true
  environment:
    type: string
    default: "staging"

flow:
  # Initialize context from inputs and environment
  - set:
      token: workflow.inputs.api_token
      env: workflow.inputs.environment
      run_id: execution.id

  # Conditional endpoint selection
  - if:
      condition: execution.context.env == "production"
      then:
        - set:
            base_url: "'https://api.example.com'"
      else:
        - set:
            base_url: "'https://staging-api.example.com'"

  # Use context values in subsequent steps
  - as: health_check
    type: http
    url: execution.context.base_url + "'/health'"
    method: GET
    headers:
      Authorization: "'Bearer ' + execution.context.token"
    timeout: 10s

  # Store result for later use
  - set:
      api_healthy: health_check.status == "success"

  - if:
      condition: execution.context.api_healthy
      then:
        - as: deploy
          type: exec
          run: ./deploy.sh
          timeout: 5m

output:
  environment: execution.context.env
  api_healthy: execution.context.api_healthy
  run_id: execution.context.run_id