Execute Sub-workflow

The Execute Sub-workflow node allows you to call a reusable workflow (a sub-workflow) from within another workflow. This enables modular workflow design — build shared logic once as a sub-workflow, then invoke it from multiple parent workflows.

Prerequisites: The target sub-workflow must be published (active) and have a Subflow Trigger as its entry point. Each workflow can have at most one Subflow Trigger.

Use Cases

Typical Applications

• Reusable Validation — Centralize input validation logic in a sub-workflow, call it from multiple workflows
• Data Enrichment — Call a sub-workflow that fetches and formats data from external APIs
• Multi-stage Pipelines — Break complex processes into stages, each implemented as a sub-workflow
• Error Handling Modules — Reuse standardized error logging and notification logic
• Loop Iteration — Call a sub-workflow inside a Loop & Iterate node to process each item

Node Configuration

Basic Settings (Parameters Panel)

1. Select Sub-workflow

Choose which sub-workflow to call from the dropdown. Only active, published workflows that include a Subflow Trigger appear in the list.

Before selection: All other settings are hidden. After selection: Input fields are automatically populated based on the sub-workflow's defined input schema.

The node always calls the latest active version of the selected sub-workflow. If the sub-workflow's trigger is later changed (e.g., replaced with a Webhook Trigger), the node will error at runtime because the sub-workflow is no longer callable.

2. Input Parameters

After selecting a sub-workflow, its expected input parameters are automatically read and displayed. Each input is a key-value pair:

Field	Description
Variable	The input name as defined in the sub-workflow
Value	The value to pass — supports expressions to reference upstream node outputs
Type	The expected data type (auto-populated from sub-workflow schema)

Supported input types:

• text — String values
• number — Numeric values
• array — List/array values
• object — JSON objects
• boolean — true / false
• datetime — Date and time values

Passing data to the sub-workflow:

// Reference upstream node output
$('Webhook Trigger').body.userId

// Reference multiple upstream nodes
$('Code').processedData

// Pass a literal value
"active"

// Pass a number
42

Required inputs: If the sub-workflow defines required inputs, you must provide values for them. The sub-workflow itself does not validate input types at the boundary — if a value of the wrong type is passed, the sub-workflow will error when a downstream node attempts to use it.

No required inputs: If the sub-workflow has no required inputs, you can leave all input fields empty and still execute the node.

3. Wait for Sub-workflow

A toggle that controls whether the parent workflow waits for the sub-workflow to complete or continues immediately.

On (default) — The parent workflow pauses until the sub-workflow finishes, then receives its output.

Execute Sub-workflow (wait = on)
  → Sub-workflow runs to completion
  → Output returned to parent
  → Parent continues with next node

Off — The sub-workflow is triggered asynchronously. The parent workflow continues immediately without waiting.

Execute Sub-workflow (wait = off)
  → Sub-workflow runs in background
  → Parent continues immediately (no output)

Warning: When Wait for Sub-workflow is off, the node outputs null. If a downstream node references the sub-workflow's output, it will error because no result is available.

Advanced Settings (Settings Panel)

Node Description

Add a custom description to document the sub-workflow call's purpose:

nodeDescription: "Calls the Order Validator sub-workflow. 
Returns { isValid: boolean, message: string }."

Output Data

When Wait is On

After the sub-workflow completes, its output data is available under this node's name in the parent workflow. The output structure is defined by the Subflow Output node(s) in the called sub-workflow.

// Access sub-workflow output in the parent
$('Execute Sub-workflow').isValid
$('Execute Sub-workflow').message
$('Execute Sub-workflow').processedAt

When Wait is Off

The node outputs null. No sub-workflow output is available to downstream nodes.

How It Works

Execution Flow

Parent Workflow:
  Trigger Node
    → Processing Nodes
    → Execute Sub-workflow Node ← gathers inputs, calls sub-workflow

Sub-workflow (called):
  Subflow Trigger ← receives inputs
    → Processing Nodes
    → Subflow Output ← packages results

Parent Workflow (continued):
    → Subsequent Nodes ← access $('Execute Sub-workflow').outputField

Version Selection

The node always calls the latest active (published) version of the selected sub-workflow. If the sub-workflow is unpublished or its trigger type is changed away from Subflow Trigger, the node will error at runtime.

Nested Sub-workflows

A sub-workflow can itself contain an Execute Sub-workflow node, enabling multi-level orchestration. Avoid circular calls (Workflow A → Workflow B → Workflow A), which will cause a runtime error.

Workflow Examples

Example 1: Simple Validation Sub-workflow

Parent Workflow:
  Webhook Trigger (POST, order data)
    → Execute Sub-workflow
        Sub-workflow: "Order Validator"
        Inputs:
          orderTotal: $('Webhook Trigger').body.total
          customerId: $('Webhook Trigger').body.customerId
        Wait: On
    → Conditional Branch
        Condition: $('Execute Sub-workflow').isValid === true
        → [valid] → Process Order
        → [invalid] → Return Error Response

Example 2: Data Enrichment with Async Call

Parent Workflow:
  Chat Trigger
    → Execute Sub-workflow
        Sub-workflow: "Customer Lookup"
        Inputs:
          customerId: $('Chat Trigger').customerId
        Wait: On
    → LLM Node
        System: "Use the following customer data to personalize your response"
        Context: $('Execute Sub-workflow')
    → Answer Node

Example 3: Fire-and-Forget with Wait Off

Parent Workflow:
  Webhook Trigger (POST, log data)
    → Execute Sub-workflow
        Sub-workflow: "Log Processor"
        Inputs:
          logEntry: $('Webhook Trigger').body
        Wait: Off                     ← Don't wait, continue immediately
    → Webhook Response (No Data)     ← Acknowledge immediately

Example 4: Loop Iteration Over Sub-workflow

Parent Workflow:
  Webhook Trigger (POST, batch of items)
    → Code Node (parse array)
    → Loop & Iterate
        Over: $('Code').items
        → Execute Sub-workflow
            Sub-workflow: "Item Processor"
            Inputs:
              item: $('Loop & Iterate').currentItem   ← Current iteration item
            Wait: On
    → Aggregate Results

Constraints

Input Type Validation

The Execute Sub-workflow node does not validate that input values match the sub-workflow's expected types. If a value of the wrong type is passed (e.g., a string where a number is expected), the sub-workflow will error at runtime when a downstream node attempts to use that value. Ensure you pass values in the expected format.

Required Inputs

Required inputs are enforced at the frontend configuration level — you must fill in values before the node can be saved. However, the backend does not re-validate required fields at runtime. If a required field is somehow empty at execution time, the sub-workflow itself will likely fail when it tries to use the missing data.

Single Subflow Trigger per Workflow

Each workflow can have at most one Subflow Trigger. If you need a sub-workflow with multiple entry points, consider creating separate sub-workflows or using conditional branching inside the sub-workflow.

No Concurrent Same-Subflow Calls with Wait Off

When Wait for Sub-workflow is off, the sub-workflow runs asynchronously. If the parent workflow calls the same sub-workflow multiple times with wait off, multiple concurrent executions are spawned. Ensure the sub-workflow is designed for concurrent execution.

Best Practices

1. Rename the Node

Double-click to rename from "Execute Sub-workflow" to a meaningful name:

[Execute Sub-workflow]        ← Default
[Validate Order]               ← Better
[Lookup Customer Profile]      ← Best

2. Document the Output Contract

Use the node description to document what outputs callers can expect:

nodeDescription: "Returns { isValid: boolean, errors: string[] }.
Check `isValid` before using downstream data."

3. Use Wait Only When You Need Output

If you don't need the sub-workflow's output, turn Wait for Sub-workflow off. This keeps the parent workflow fast:

# Need output — keep wait on
Wait: On → $('Execute Sub-workflow').result

# Fire-and-forget — turn wait off
Wait: Off → Parent continues immediately

4. Handle Sub-workflow Errors

The Execute Sub-workflow node has an error output port. Connect it to error handling nodes:

Execute Sub-workflow
  → [Success Port 0] → Continue processing
  → [Error Port] → Log Error → Send Alert

5. Test Sub-workflows Independently First

Before calling a sub-workflow from a parent, test it independently using its own trigger to ensure it works correctly. This isolates issues and speeds up debugging.

FAQ

Q1: Can I call a workflow that doesn't have a Subflow Trigger?

A: No. The target workflow must have a Subflow Trigger. If the workflow's trigger is changed away from Subflow Trigger, the node will error with "Subflow not found".

Q2: What happens if the sub-workflow fails?

A: When Wait is on, the node outputs an error through its error port. You can connect the error port to logging, notification, or fallback nodes. When Wait is off, the failure happens asynchronously and does not affect the parent workflow.

Q3: How are sub-workflow versions handled?

A: The node always calls the latest active (published) version of the selected sub-workflow. If you publish a new version of the sub-workflow, the node will automatically use it on the next execution. There is no way to pin to a specific version.

Q4: Can I pass complex objects as inputs?

A: Yes. Use expressions to reference objects, arrays, or any upstream data:

// Pass an object
$('Code').customerProfile

// Pass an array
$('Code').itemList

// Pass a nested field
$('HTTP Request').body.data.attributes

Q5: What if I need to pass many inputs?

A: Consider using a Code Node to aggregate data into a single object before passing it to the sub-workflow. This keeps the Execute Sub-workflow node's input list manageable.

Q6: Can I call the same sub-workflow multiple times in one parent?

A: Yes. You can place multiple Execute Sub-workflow nodes in the same parent workflow, each with different inputs. When Wait is on, they execute sequentially. When Wait is off, they run concurrently.

Next Steps

• Sub-workflow Tool Node — Register sub-workflows as AI-callable tools
• Subflow Trigger — Learn how to create a callable sub-workflow
• Subflow Output — Learn how sub-workflows return results
• Loop & Iterate — Call a sub-workflow for each item in a list

Related Resources

• Webhook Response Node — Send custom HTTP responses
• Code Node — Process data before passing to sub-workflow
• Conditional Branch — Route based on sub-workflow output