Two tickets can be cheaper than one
Wingman now joins separate low-cost flights through a hub, the way Kiwi does, and can price a round trip as one booking. Whichever comes out cheaper wins.
Google Flights lists connections that one booking covers. Often the cheapest way there isn't one of them. It's two separate low-cost flights through a hub, each booked on its own.
Self-transfers
Turn on self-transfer for a route and Wingman also searches each day in two halves, through the hubs where cheap connections tend to be. It joins flights that land and leave the same airport with at least 90 minutes to change. Overnight connections count when your travel time leaves room for them, and a city with several airports counts as one: land at Stansted, leave from Gatwick, with time to cross London.
Wingman learns where the cheap connections are as it goes, and a new watch tries them in its very first results, not days later. Prague to Cagliari through Milan can cost half the cheapest single ticket.
A self-transfer is two tickets, and Wingman says so every time: book both, and a missed connection is yours to sort out.
Round-trip tickets
It works the other way too. Full-service airlines often sell a round trip for much less than two one-way tickets: Prague to Da Nang and back came to 26 600 Kč as one booking, against 37 500 Kč as two. With round-trip tickets on, a trip is also priced as one booking both ways, and the cheaper of the two counts.
Before any of this went out, the search was measured against an exhaustive search of every hub and against Kiwi's own results, and the gaps were closed.