Parameter References

Template Syntax

Use {{double braces}} to reference workflow inputs and previous step outputs in your step parameters.

Reference Types

Reference	Description	Example
`{{inputs.field}}`	Workflow input field	`{{inputs.prompt}}`
`{{step_id.output}}`	Full output of a step	`{{generate_text.output}}`
`{{step_id.primary}}`	Primary output of a step	`{{step1.primary}}`

Examples

Referencing Inputs

{
  "step_id": "generate_text",
  "type": "model",
  "model": "openai-chatgpt-5",
  "params": {
    "system_prompt": "You are a helpful assistant",
    "user_prompt": "{{inputs.prompt}}"
  }
}

Chaining Steps

{
  "steps": [
    {
      "step_id": "step1",
      "type": "model",
      "model": "openai-chatgpt-5",
      "params": {
        "user_prompt": "{{inputs.prompt}}"
      }
    },
    {
      "step_id": "step2",
      "type": "model",
      "model": "flux-1-1-pro",
      "params": {
        "prompt": "{{step1.output}}"
      }
    },
    {
      "step_id": "step3",
      "type": "model",
      "model": "topaz-upscale-image",
      "params": {
        "image": "{{step2.primary}}",
        "scale": 2
      }
    }
  ]
}

Embedding in Strings

Template variables can be embedded within larger strings:

{
  "prompt": "A portrait of {{inputs.name}} in {{inputs.style}} style"
}

Referencing Parallel Branch Outputs

When a parallel step completes, you can reference outputs from its branches using the branch step IDs:

{
  "steps": [
    {
      "id": "step1",
      "type": "parallel",
      "branches": [
        {
          "name": "Video",
          "steps": [{"id": "step1_branch_0", "type": "model", "model": "veo-3", "params": {"prompt": "{{inputs.prompt}}"}}]
        },
        {
          "name": "Image",
          "steps": [{"id": "step1_branch_1", "type": "model", "model": "flux-2-max", "params": {"prompt": "{{inputs.prompt}}"}}]
        }
      ]
    },
    {
      "id": "step2",
      "type": "model",
      "model": "topaz-upscale-image",
      "params": {
        "image_url": "{{step1_branch_1.primary}}"
      }
    }
  ]
}

Condition Expressions

Choice steps use $ reference syntax (not {{template}} syntax) to evaluate conditions:

Reference	Description	Example
`$.inputs.field`	Workflow input	`$.inputs.email`
`$.step_id.primary`	Primary output of a step	`$.step1.primary`
`$.step_id.output`	Full output of a step	`$.step1.output`
`$.step_id.output.field`	Nested field from step output	`$.step1.output.filename`

{
  "condition": {
    "expression": "$.step1.primary",
    "operator": "string_matches",
    "value": ".mp4"
  }
}

You can also access nested output fields:

{
  "condition": {
    "expression": "$.step1.output.filename",
    "operator": "string_matches",
    "value": ".pdf"
  }
}

Condition expressions use $.step_id.field syntax, while step parameters use {{step_id.field}} template syntax. These are different reference systems.

For the full list of condition operators (comparison, string, array, existence, and logical), check out Workflow Structure: Condition Operators.

Resolution

Template variables get resolved at execution time. Here’s what the workflow engine does under the hood:

Evaluates steps in order
Executes parallel branches concurrently
Evaluates choice conditions and routes to the matching branch
Resolves template variables using actual values from inputs and completed steps
Passes the resolved parameters to the model

If a referenced step hasn’t completed or doesn’t exist, the execution will fail. So make sure your references point to steps that actually run before they’re needed!

Overview

Concepts

API Reference

OpenAPI Reference

Webhooks

Examples

Parameter References

Template Syntax

Reference Types

Examples

Referencing Inputs

Chaining Steps

Embedding in Strings

Referencing Parallel Branch Outputs

Condition Expressions

Resolution

​Template Syntax

​Reference Types

​Examples

​Referencing Inputs

​Chaining Steps

​Embedding in Strings

​Referencing Parallel Branch Outputs

​Condition Expressions

​Resolution

Template Syntax

Reference Types

Examples

Referencing Inputs

Chaining Steps

Embedding in Strings

Referencing Parallel Branch Outputs

Condition Expressions

Resolution