Execution Witness Ledger: Prove Which Nodes Run On An Idle IF Branch Before Merge

How it works

1. 1.Manual Trigger fires the template with one empty item.
2. 2.Generate Sample Records builds four demo JSON records (valid and invalid) and normalizes status with type checks.
3. 3.Route Active Vs Idle (IF, strict) sends active records to output 0 and intentionally leaves output 1 empty.
4. 4.A NoOp witness on each path represents an observable downstream node.
5. 5.A Code witness on each path records {witness, branch, executed, itemCount, validRecords} and returns nothing when no items arrive.
6. 6.Merge (append, 2 inputs) joins whichever witness reports exist, one branch per input index.
7. 7.Build Witness Ledger compares the expected roster with the recorded reports and outputs one row per witness plus LEDGER_SUMMARY.

Use cases

• Verify idle-branch behaviour on your current n8n version before shipping a multi-branch flow
• Diagnose the No Merge Data Found error caused by an always-empty IF branch
• Keep a per-run record of which nodes actually executed for engineering reviews
• Teach Merge append input indexing safely

Requirements

• n8n 2.47.3 with manualTrigger, Code, If, Merge, NoOp and StickyNote nodes
• No credentials and no network access required
• For real data: replace the records array or wire your source into the IF node using {id, customer, amount, status}

Setup and testing in n8n

1. Import the JSON into n8n and click Execute Workflow.
2. Confirm three output items: active witness executed=true with itemCount 4, idle witness executed=false with itemCount 0, and the summary.
3. Edge case: change one record status to 'closed' and rerun; both witnesses become executed=true with split counts.
4. Edge case: empty the records array; a single invalid placeholder item is produced and Merge still completes.

Service Value

Ready-made workflow template for automation delivery and service execution.