Gather node

The Gather node joins parallel branches back into one, when all, any or a set number of them arrive, with an optional timeout.

The Gather node (code name Join) brings parallel branches back together. Gather is the only node that accepts multiple inbound branches. It waits until enough of its incoming tracks have arrived, then continues once.

When to use it

Use Gather wherever two or more branches that ran in parallel should meet again. For example, after a Start node fans out into "send the consent form" and "book the scan", continue only when both are done.

If several connections enter any other node, its card shows n incoming branches — consider Gather, and the review panel warns about it. Without a Gather, the next step can run once for each branch that arrives.

Configuration

Field	What it does	Options and default
Label, Notes	See Label and Notes.	—
Policy	How many incoming tracks must arrive.	All — every still-live incoming track (default), Any — the first arrival completes, K of N — author sets k.
k	Shown for K of N. How many incoming tracks must arrive.	Whole number, at least 1. The box shows 1 until you change it.
Timeout: Amount, Unit	How long to wait for the other tracks, counted from the first arrival. When it runs out the timeout edge fires.	Unit: minutes, hours, days. 0 means no timeout.
If this step is already in the past	See If this step is already in the past.	Follow the journey.

The panel also notes: Dead branches are excluded; Gather resets per round.

Outcomes and branches

Outcome	When
met	The policy was satisfied: all still-live tracks, the first track, or k tracks arrived.
timeout	The timeout ran out before the policy was met.
impossible	K of N only: so many tracks ended elsewhere (for example at a Close with scope Branch) that k can no longer be reached. If no connection is bound to impossible, the journey takes the timeout path instead.

In the edge editor, pick met, timeout or impossible in the Outcome list of each connection leaving the Gather.

What happens when it runs

The first track to arrive starts the Gather and, if a timeout is set, starts the clock.
Each later arrival is counted. Tracks that have already ended on another path are left out of All, so the Gather does not wait for a branch that will never come.
As soon as the policy is met, the journey continues once, along the met path. With K of N, if k can no longer be reached, it continues along impossible. If the clock runs out first, it continues along timeout.
The Gather then resets, so if the journey loops back through the same tracks it gathers again for the next round.

Patients and staff see nothing at a Gather.

Example

Admit only when both pre-admission steps are done, or escalate after 2 days.

From the previous step, draw two plain connections: one to a Capture step (pre-admission form), one to a Sign step (consent).
Connect both steps' onward paths into one Gather.
Policy: All. Timeout: 2 days.
Connect met to the admission booking and timeout to an Engage step that asks the front desk to chase the patient.

Tips and limitations

Set a timeout. Without one, the review panel warns has no timeout branch — convergence may wait forever.
With K of N, the review panel warns if k is larger than the number of incoming tracks, because the Gather could never be met.
The timeout counts from the first arrival, not from when the journey started.

Check the panel, not the card

The node card shows No timeout — publish will warn even when you have set a timeout in this panel. With K of N, type the value of k yourself: if you leave the box at the 1 it shows, the Gather waits for every incoming track.

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