Merge

Combine the items of multiple inputs — append, combine by matching fields / position / all combinations, or choose one branch.

Finding it in the library

Search the builder's node library for Merge (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.

Library capture pending — regenerate with npm run shots:nodes.

Wired up in the builder

Merge 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.

Canvas capture pending — regenerate with npm run shots:nodes.

How it’s configured

The node’s Configure panel as it opens in the builder when you select the step — every setting laid out with real values. Click any field to edit it.

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.

Input handles follow `numberInputs` (Input 1 … Input N, 2–10). Combine-by-matching-fields always uses exactly two inputs.

How data flows through it

Merge 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

None of this node’s properties are string-typed, so {{ }} expressions don’t apply here — JSON- and code-typed fields are always taken 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 (Merge) works as well as the exact type id (logic.merge).

In the Copilot panel (or any connected AI):

add a merge node after the trigger

As a step in a create_chain_workflow call:

{"type":"Merge","config":{}}

curl -s -X POST http://localhost:48170/mcp -H "content-type: application/json" -d '{ "jsonrpc": "2.0", "id": "1", "method": "tools/call", "params": { "name": "add_node", "arguments": { "workflowId": "<id>", "type": "Merge" } } }'

Example input & output

Captured from a real test run of the workflow above — this is what you see in the run data panel after pressing Test workflow.

[
  [
    {
      "id": 1,
      "a": true
    }
  ],
  [
    {
      "id": 2,
      "b": true
    }
  ]
]

[
  {
    "id": 1,
    "a": true
  },
  {
    "id": 2,
    "b": true
  }
]

Property reference

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

Using it

Join two branches by position

In the capture above, two sources fan in to one Merge — each branch lands on its own input pin (Input 1, Input 2), and the example output shows the result: one list containing both items. That is append mode, the default.

Switching Mode to combine and Combine by to position pairs item n of Input 1 with item n of Input 2 into a single merged object — the classic “fork, do two things, join the results” shape. Clash handling decides which side wins when both branches produced the same field; because the engine orders inputs by target port, “prefer Input 2” is a stable, meaningful choice, not a race.

Join two datasets by key

Combine by matching fields is the SQL-ish join: in Fields to match, add a row pairing the key field of Input 1 (say id) with the key field of Input 2 (say orderId). Join mode picks the family — keep matches (inner join), keep non-matches, or keep everything (enrich) — and Output data from chooses whether merged items carry both sides or just one.

Tips

• Input order is deterministic. The engine orders by target port — input1 is Input 1, always — so “which branch wins on a field clash” is a real, stable choice.
• Number of inputs redraws the node’s input pins live (2–10). Combine-by-matching-fields always uses exactly two.
• chooseBranch mode passes one input through untouched (or a single empty item) — useful as an explicit synchronization point.
• Merge emits a list. If exactly one item comes out and the next node wants the bare item, follow with Limit and its unwrapSingle option.
• Fuzzy compare treats 3 and "3" as equal when matching fields.

Related nodes

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

• Filter / Condition Evaluates a condition against input and returns the pass/fail decision.
• IF Routes input to a true or false output based on a typed condition.
• Switch Routes input to one or more named outputs based on ordered conditions.
• Rate Limit Multi-tenant rate limiting: identifies the caller by a tenant GUID header, enforces per-second/minute/hour/day
• Loop Over Items Iterate a list: run the inside body once per batch of items, then emit everything on done.
• Thread Pool Queue-fed concurrency frame: consume from the input queue, run the inside body on a pool of threads, publish e
• Wait Pauses the flow for a duration or until a timestamp, then passes the input through unchanged
• Wait for Approval Pauses the run until a human approves or rejects, then routes the input (plus the decision) out the matching p

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. The hand-authored notes above are merged in.