Junction

logic.junction Logic v0.1.0

A point on a wire that flow can come back through: wire any node further down into its Return port and everything after the junction runs again, with the pass number on $pass and a marker on the data.

The Junction step on the Studio canvas — The **Junction** step as it appears on the Studio canvas — input pins on the left, output ports on the right.

Finding it in the library

Search the builder's node library for Junction (it lives under Logic). A single click opens the in-editor docs panel shown here — description, ports, and every property, without leaving the canvas. Double-click (or drag) to add it to the workflow.

Junction in the node library, with the in-editor docs panel open — The library entry and the in-editor docs panel for **Junction** — the same reference this page is generated from.

Wired up in the builder

Junction in a real, runnable flow — captured live from the Studio editor, exactly as it looks on your canvas. This is the same workflow used for the example input & output below.

Junction wired into a runnable workflow in the Studio builder — **Junction** wired into a runnable flow — input on the left, output on the right.

How it’s configured

The node’s settings as the builder shows them — every field laid out with real values. In the Studio these are edited on the node: click the chevron on the divider under its ports to open them.

Config capture pending — regenerate with npm run shots:nodes. See the full property reference below.

Ports

Ports are the node’s contract with its neighbours. In the editor a port label renders bold when wired and italic when optional; ◈ ports accept attachment carriers rather than data wires.

Direction	Port	Label
Input	`input`	Input
Input	`return`	Return
Output	`output`	Output
Output	`limit`	Limit

How data flows through it

Junction consumes the content of the incoming envelope — when it is fed directly by a trigger, the trigger’s wrapper is unwrapped at the node boundary so the node sees the actual data, not the metadata shell. Its output becomes the payload for the next node, while the envelope (trace ids, correlation, binary refs) rides along untouched. In the Runs view you always see the whole envelope for both sides of this node.

Expressions in the config

String-typed properties accept {{ }} expressions evaluated against the incoming item at run time — e.g. {{ $json.customer.email }}. On this node that’s stampKey. JSON- and code-typed fields never interpolate — they are passed through literally.

Build it with AI

Every node in this reference is reachable through Flowdrome’s AI Copilot and the MCP tools — say what you want, and the graph surgery happens server-side. Node types resolve fuzzily, so the catalog label (Junction) works as well as the exact type id (logic.junction).

In the Copilot panel (or any connected AI):

add a junction node after the trigger

As a step in a create_chain_workflow call:

{"type":"Junction","config":{}}

Raw MCP call — add this node to a workflow with add_node

curl -s -X POST http://localhost:4800/mcp -H "content-type: application/json" -d '{ "jsonrpc": "2.0", "id": "1", "method": "tools/call", "params": { "name": "add_node", "arguments": { "workflowId": "<id>", "type": "Junction" } } }'

Example input & output

Captured from a real test run of the workflow above — this is what the Runs view shows after pressing Test workflow.

Input — what the node received

The Junction node's input envelope in the run data viewer — The input envelope in the Runs view — Flowdrome always shows the whole envelope, with the payload inside `body`.

Output — what the node produced

The Junction node's output envelope in the run data viewer — The output envelope after the step ran.

Property reference

Every setting, with its type and default — the same fields shown configured above.

Property	Type	Default	Description
Maximum runs `maxPasses`	`int`	`10`	How many times data may go through this junction, counting the first pass. Going round ten times is fine when that is the logic — this only stops a loop that can never end. The run PAST this number leaves on the Limit output instead of Output, so the flow can report and stop; the run still succeeds. Coming back again after that fails the run.
Mark returning data `stamp`	`boolean`	`true`	Add the run marker to the data on every run after the first. Its PRESENCE is the "came back through again" signal — {{ $json.junction }} is truthy only on a repeat — and it carries { pass, from }. The first pass is never marked, so a junction sitting straight after a trigger stays completely transparent.
Marker field `stampKey`	`string`	`"junction"`	Field the marker is written to. Non-object data (a list, a string, a number) is NEVER wrapped or rewritten — it passes through untouched and the run number stays on $pass, with a warning on the node saying so. Shown when `stamp !== false`

Related nodes

The rest of the Logic group — the same folder you’d scan in the editor’s library.

This page is generated from the node registry by gen-node-docs.mjs on every site build — ports, properties, defaults and visibility rules cannot drift from the code. The screenshots and example data are captured from a live Flowdrome by npm run shots:nodes and npm run gen:examples.