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Template Expressions

Template expressions let you pass data between workflow steps and inject runtime inputs using {{variable}} syntax.

Syntax​

ExpressionResolves To
{{variable}}Runtime input passed via --input variable=value
{{step_id.output}}Output from a previous step
{{step_id.output.field}}Specific field from a step's output

Examples​

Runtime Inputs​

{
  "input": { "path": "{{docs_path}}" }
}
vai workflow run my-workflow.json --input docs_path=./docs

Step Output References​

{
  "id": "embed",
  "depends": ["chunk"],
  "input": { "texts": "{{chunk.output}}" }
}

The embed step receives the output of the chunk step as its texts input.

Nested Field Access​

{
  "input": { "query_vector": "{{embed-query.output.vector}}" }
}

Tips​

  • Step outputs are only available to steps that declare a dependency via depends
  • Template expressions are resolved just before each step executes
  • Use descriptive step IDs so template expressions read naturally