Variable Assignment — Input & Output

Output Ports

Port	Condition	Description
success	Assignment completed without error	The variable was written to workflow memory. The workflow continues along this port. Downstream nodes can immediately read the variable using `var.variableName`.
error	Expression evaluation failed or invalid variable name	An error occurred while evaluating `value_expression`, or the variable name is invalid. The error port carries an error object with `message` and `code` fields. If no error handler is connected, the workflow halts.

What Gets Written to Memory

Variable Assignment does not produce a traditional node output object. Instead, it writes directly to the workflow's execution memory store (a key-value map scoped to the current run). The written entry is then accessible to all downstream nodes.

Memory vs. Node Output

Variable Assignment has no output.* object — it does not produce node output data. The sole side-effect is writing to var.* memory. To access the value downstream, always use var.variableName, not output.NodeName.*.

Referencing Variables Downstream

Expression Syntax	What It Does	Example
`{@ var.variableName }`	Reads the current value of a workflow variable by name	`{@ var.invoiceTotal }` → `1234.56`
`{@ var.myObj.property }`	Reads a nested property from an object stored as a variable	`{@ var.customer.address.city }` → `"Austin"`
`{@ var.myArray[0] }`	Reads an element from an array stored as a variable	`{@ var.lineItems[0].amount }` → `99.99`
`{@ var.counter + 1 }`	Performs arithmetic on a numeric variable inline	Useful in loop accumulators without needing a separate CodeExecute node

Example: Memory State After Two Assignments

After running two Variable Assignment nodes sequentially:

// Node 1: AssignCustomerId
// variable_name: "customerId", value: "CUST-7891"

// Node 2: AssignOrderTotal
// variable_name: "orderTotal", value_expression: "{@ $input.current.subtotal + $input.current.tax }"

// Resulting workflow memory:
{
  "customerId":  "CUST-7891",
  "orderTotal":  582.40
}

// Any downstream node can reference:
// {@ var.customerId }  →  "CUST-7891"
// {@ var.orderTotal }  →  582.40

Error Output Schema

When the error port fires, the following object is available via output.NodeName.error:

{
  "error": {
    "code": "EXPRESSION_EVAL_ERROR",
    "message": "Failed to evaluate value_expression: undefined variable 'missingVar'",
    "node": "StoreInvoiceTotal",
    "timestamp": "2026-05-23T10:34:12Z"
  }
}