Merge

Accepts N incoming edges and fires its single outgoing edge based on a wait policy. Use this to rejoin parallel branches or to wait until several conditions have fired.

When to use

• You fanned out with Parallel Split and now need to wait for all branches before continuing.
• You have multiple upstream paths that each "might" run, and you want the workflow to continue as soon as at least one does.
• Synchronising multiple loop iterations before a final step.

Configuration

Field	Required	What it does
mode	Yes	wait_all (default) or first_wins.

Modes

• Wait for All (wait_all): Merge fires its output only when every incoming edge has delivered. If any upstream branch terminates early (due to a filter or condition), Merge will wait forever. Make sure every incoming edge either delivers or the branch is structured so that the Merge's input from that branch isn't relied upon.
• First Wins (first_wins): Merge fires its output as soon as any incoming edge delivers. Remaining upstream branches continue running to completion but their arrivals at the Merge are ignored.

What it outputs

The payload from the arriving branch(es) is written to the Merge node's context. With wait_all, the context contains a merged view keyed by the source branch's node IDs.

Gotchas

• Merge deadlock: if an upstream branch never produces a result (e.g. it's gated by a filter that always drops), wait_all blocks indefinitely. Check your upstream routes end in a Merge input only when they actually deliver.
• Merge is re-entrant: unlike most nodes, Merge can be entered multiple times during a single execution. The engine tracks arrivals per merge instance.