$output.{nodeId} — Named Node Output

Syntax

// $output.{nodeId}.{field}
$output.fetch-customer.customerId
$output.fetch-customer.tierLevel
$output.validate-order.isValid
$output.validate-order.errorMessages[0]

// Accessing the entire output object (when the downstream node needs the full object)
$output.parse-json    // Returns the full output of the parse-json node

How nodeId Maps to Memory

The expression engine resolves $output.{nodeId} by calling ExecutionMemory.GetNodeOutput(nodeId). The nodeId in the expression must exactly match the nodeId set in the workflow canvas. Node IDs are case-sensitive.

// ExpressionContext.cs (simplified)
"$output" => nodeId => _executionMemory.GetNodeOutput(nodeId)

// So $output.fetch-customer.tierLevel resolves as:
var node = _executionMemory.GetNodeOutput("fetch-customer");  // dynamic lookup
var result = node?.tierLevel;  // property navigation

Fan-In Pattern — Multiple Upstream Nodes

$output.{nodeId} is the correct choice when a node has multiple upstream connections and needs to reference specific ones by identity.

// MergeNode configuration — referencing two specific upstream nodes by ID
{
  "leftDataset"  : "{{$output.left-transform}}",
  "rightDataset" : "{{$output.right-transform}}",
  "mergeKey"     : "customerId"
}

// Condition node — decision based on outputs from two non-adjacent nodes
$output.credit-check.approved == true && $output.fraud-score.riskLevel == "low"

Null Semantics

$output.{nodeId} returns null if the named node has not yet run. This is the most common source of silent expression errors in branching workflows.

Naming Node IDs in Flow Studio

Workflow designers set node IDs in the node configuration panel in Flow Studio. A meaningful, stable ID is critical for reliable $output references. Default IDs like node-1 are fragile.

// Best practice — use descriptive, hyphen-separated IDs
$output.fetch-customer        // Good — clear and stable
$output.validate-order        // Good
$output.node-1                // Bad — meaningless, fragile if node is moved/replaced
$output.FetchCustomer         // Acceptable — camelCase is also supported