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
{
"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"
}
}
{
"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.
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!
