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Overview

We’ve updated our workflow syntax to make data flow more explicit and consistent. These changes improve readability and make workflows more maintainable. While this update requires modifications to existing workflows, it provides a more robust foundation for workflow development.

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1. Input/Output Data References

The most significant change is how we reference input and output data between workflow steps. The new syntax makes the data flow more explicit by using the steps keyword.

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Old Syntax:

  • inputs[x] - Referenced input data from step x
  • outputs[x] - Referenced output data from step x
  • _x - Shorthand for input data from step x

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New Syntax:

  • steps[x].input - References input data from step x
  • steps[x].output - References output data from step x
  • _x - Has been removed

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Example

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Old Syntax

- evaluate:
    input_data: inputs[0].a
    output_data: outputs[0].b
    shorthand: _0.c

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New Syntax

- evaluate:
    input: $ steps[0].input.a
    output: $ steps[0].output.b
    shorthand: $ steps[0].input.c

Notice the addition of the $ prefix in the new syntax. This indicates that the value should be treated as a Python expression. We’ll cover this in detail in the next section.

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Key Changes:

  • inputs[0] becomes steps[0].input
  • outputs[0] becomes steps[0].output
  • _0 becomes steps[0].input
  • Added $ prefix to indicate Python expressions

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2. Template Syntax Changes Inside prompt Steps

Another significant change is the removal of Jinja templates ({{ }}) in log steps and prompt steps. Instead, we now use Python f-strings with the $ prefix for dynamic content.

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Old Syntax (Using Jinja):

- prompt:
    - role: user
      content: Write me an article about the topic: {{inputs[0].topic}}

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New Syntax (Using f-strings):

- prompt:
    - role: user
      content: $ f"Write me an article about the topic: {steps[0].input.topic}"
    - role: user
      content: this is only text, no need for dollar sign prefix

For multiple lines, you can use a multiline f-string:

- prompt:
    - role: user
      content: |-
        $ f"""
        Write me an article about the topic: {steps[0].input.topic}.
        The article should be {steps[0].input.article_length} words long.
        """

The $ prefix is only needed when the value contains a Python expression or f-string. Plain text content doesn’t require the prefix.

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3. When to Use the $ Prefix

The $ prefix should be used in two scenarios:

  1. When referencing step data (inputs/outputs)
  2. When using Python expressions or f-strings

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Examples:

steps:
  - prompt:
      # Needs $ because it uses an f-string
      - role: user
        content: $ f"The temperature is {steps[0].input.temp}°C"
      
      # No $ needed - plain text
      - role: user
        content: Tell me about the weather

  - evaluate:
      # Needs $ because it references step data
      input: $ steps[0].output
      
      # Needs $ because it's a Python expression
      condition: $ len(steps[0].input.text) > 100
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