Break not scheduled after a constrained delivery - shipment dropped as unassigned

[jlannoy]

When a shipment keeps the vehicle loaded right up to a delivery time window, and a break's time window opens at/after that delivery deadline, VROOM does not place the break after the drop-off. Instead it reports the shipment as unassigned, even though a valid solution exists (deliver, then take the break while empty, then return).

It looks like the break is only considered for placement in the idle time before the delivery (where the vehicle is still loaded), and is never deferred to the empty period after the delivery.

To reproduce :

{
  "vehicles": [
    {
      "id": 1,
      "profile": "car",
      "start_index": 0,
      "end_index": 0,
      "time_window": [28800, 57600],
      "breaks": [
        { "id": 1, "service": 1800, "time_windows": [[40800, 50400]] }
      ]
    }
  ],
  "shipments": [
    {
      "pickup":   { "id": 10, "location_index": 1, "service": 0 },
      "delivery": { "id": 11, "location_index": 2, "service": 0,
                    "time_windows": [[39900, 40800]] }
    }
  ],
  "matrices": {
    "car": {
      "durations": [
        [   0, 1800, 1800],
        [1800,    0, 1800],
        [1800, 1800,    0]
      ]
    }
  }
}

Here the delivery window is [39900, 40800] (11:05–11:20) and the break window is [40800, 50400] (11:20–14:00), i.e. it opens only after the delivery deadline — so the only possible placement is after the drop-off.

Expected:
one route, 0 unassigned. A valid schedule exists, e.g.
start → pickup(10) → delivery(11) @ 40800 → break(1) @ 40800–42600 → end @ 44400, all within the vehicle and break windows.

Actual: code:
0, summary.unassigned: 2, with pickup 10 and delivery 11 unassigned and no route using the vehicle.

Additional notes:

• Removing the breaks entry makes the problem solvable (the route itself is feasible).
• Widening the break window so it opens before the loaded leg (e.g. [28800, 57600]) also makes it solvable — the break is then placed before/around the delivery. The problem only appears when the break window opens during/after the loaded delivery leg, when an after-delivery placement is required.
• Adding "max_load": [0] to the break (break only when empty) does not change the outcome.

[jcoupey]

Thanks for sharing, I can reproduce the problem. That shipment ends up unassigned, probably for some reason related to the break placement logic, but the expected ordering you suggest is valid indeed.