On Variable Update Node

The On Variable Update node triggers your workflow when a specific application variable is updated. This enables reactive patterns where one part of your system can signal another to take action.

When to Use

State-driven workflows - React to status changes in your application
Threshold monitoring - Trigger when counters or metrics cross thresholds
Data synchronization - Propagate changes across systems
Event broadcasting - One workflow updates a variable, others react
Decoupled logic - Separate “what happened” from “what to do about it”

Example: Order Status Notifications

Notify customers when their order status changes:

Set up the variable monitor

Add an On Variable Update node:

Variable name: order_status
Change type: any

Determine notification content

Use a Multi-Condition node on {{variable_changed_1.newValue}}:

processing → “Your order is being prepared”
shipped → “Your order is on the way”
delivered → “Your order has been delivered”

Send the notification

Connect to an External API (email or SMS) node to notify the customer.

Workflow structure:

├── On Variable Update (order_status)
├── Multi-Condition (based on new status)
│   ├── processing → Ask AI (prepare email) → External API (send email)
│   ├── shipped → Ask AI (prepare email + tracking) → External API
│   └── delivered → Ask AI (feedback request) → External API

Example: Threshold Alert

Alert when error count exceeds a threshold: Monitor workflow:

├── On Variable Update (error_count, increase)
├── Condition (newValue > 10)
│   ├── Met: External API (Slack alert)
│   └── Unmet: (no action)

Configuration:

Variable: error_count
Change type: increase

Then in your Condition node:

{{variable_changed_1.newValue}} > 10
AND {{variable_changed_1.previousValue}} <= 10

This ensures you alert only when crossing the threshold, not on every increase.

Example: Configuration Propagation

Update multiple systems when a configuration changes:

Workflow: Config Propagator
├── On Variable Update (api_rate_limit)
├── Loop (over list of services)
│   └── HTTP Request (update service config)
└── External API (Slack - notify team of change)

This pattern keeps distributed systems in sync when central configuration changes.

Use Patterns

Event Broadcasting

One workflow sets a variable, multiple workflows react:

Workflow A (main process):
└── Update Variable (status = "complete")

Workflow B (notifications):
├── On Variable Update (status, specific: "complete")
└── External API (send notifications)

Workflow C (cleanup):
├── On Variable Update (status, specific: "complete")
└── Execute Code (archive data)

State Machine

Build state machines where transitions trigger actions:

Variable: application_state
Values: draft → review → approved → published

Workflow: State Transition Handler
├── On Variable Update (application_state)
├── Multi-Condition
│   ├── review → External API (notify reviewers)
│   ├── approved → External API (notify author)
│   └── published → Execute Code (update search index)

Counter-Based Triggers

Trigger actions based on accumulated counts:

# When signup count reaches milestones
├── On Variable Update (signup_count, increase)
├── Condition (newValue % 100 == 0)
│   └── Met: External API (celebrate milestone in Slack)

Tips

Use specific value triggers when you care about a particular state, and any triggers when you need to react to all changes.

Access both previousValue and newValue to implement transition logic - different actions for different state changes.

Avoid circular dependencies where a variable change triggers a workflow that changes the same variable. This can create infinite loops.

Variable changes from Update Variable nodes within the same workflow don’t trigger On Variable Update events in that same workflow run. This prevents self-triggering.

Settings

string

default:"On Variable Update"

Display name shown on the canvas.

string

default:"variable_changed_1"

Unique identifier for referencing outputs.

string

required

The name of the application variable to monitor.

string

default:"any"

What type of change to trigger on:

any - Any change to the variable
specific - Only when changed to a specific value
increase - When numeric value increases
decrease - When numeric value decreases

any

For specific change type: the value that triggers the event.

Outputs

string

Name of the variable that changed.

any

The value before the change.

any

The current value after the change.

string

ISO timestamp of when the change occurred.

string

Identifier of what triggered the change (workflow ID, node key, or “manual”).

Update Variable

Update variables that trigger this event.

Condition

Add logic based on the changed value.

Overview

Triggers

Actions

Logic

Communication

On Variable Update Node

When to Use

Example: Order Status Notifications

Example: Threshold Alert

Example: Configuration Propagation

Use Patterns

Event Broadcasting

State Machine

Counter-Based Triggers

Tips

Settings

Outputs

Update Variable

Condition

​When to Use

​Example: Order Status Notifications

​Example: Threshold Alert

​Example: Configuration Propagation

​Use Patterns

​Event Broadcasting

​State Machine

​Counter-Based Triggers

​Tips

​Settings

​Outputs

​Related Nodes

Update Variable

Condition

When to Use

Example: Order Status Notifications

Example: Threshold Alert

Example: Configuration Propagation

Use Patterns

Event Broadcasting

State Machine

Counter-Based Triggers

Tips

Settings

Outputs

Related Nodes