Pre/Post-Merge Key Manifest Reconciliation with Empty-Branch Sentinel

How it works

1. 1.Manual Trigger runs a code node emitting fictional items with unique id and optional branch
2. 2.The sample fans out to two parallel manifest nodes; each filters its branch (explicit A, everything else under B) and separates corrupt items (non-string or empty id) into invalid_count
3. 3.Each node attaches branch_manifest to the first passing item only, and emits a manifest_only sentinel item if the branch has no valid items
4. 4.A Merge in append mode combines both outputs; the sentinel guarantees non-empty inputs so execution never stalls
5. 5.A runOnceForAllItems code node emits one report: pre/post counts, empty_branch (received_count=0), all_items_invalid, invalid_count and missing keys
6. 6.An IF on ok routes through Set nodes adding outcome=reconciliation_passed or outcome=keys_lost_alert with missing_keys_detail, then a noOp per path

Use cases

• Verifying completeness of conditional path merges in n8n without stalling on empty branches
• Detecting silent item loss between branching and merging
• Distinguishing empty branches from branches whose items are all corrupt in reconciliation reports

Requirements

• n8n 2.44.4 or newer with executionOrder=v1
• No credentials and no external calls
• For production: replace the sample node with real input; each item needs a unique string id, an optional branch of A or B (missing branch counts under B); never use drop outside testing

Setup and testing in n8n

1. Import the JSON and run Manual Trigger: expect the keys_lost_alert path detecting B-202 with missing_keys_detail='B: B-202' and branch B invalid_count=1
2. Remove drop:true from B-202 and run: expect ok=true on the reconciliation_passed path
3. Delete all branch A items in the sample node and run: expect completion with empty_branches=['A'] and ok=true via the reconciliation_passed path (sentinel prevents stalling)
4. Make all branch A items have invalid ids and run: expect empty_branch=false with all_items_invalid=true and invalid_count=3

Service Value

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