Halvorsen won the U23 road race at the World Championships at Doha in 2016, one of a number of successes he achieved before turning pro, including the 2017 Handzame Classic and two stages at the Tour de l'Avenir plus the points classification in 2017.
This season the 23-year-old took a stage win apiece at the Herald Sun Tour and the Tour of Norway. He's the fourth Norwegian to ride for the team, after Thor Hushovd and Gabriel Rasch in 2011 and Kristoffer Skjerping from 2015 to 2016.
"From day one, I got a good feeling for EF and their desire to rely on me as a sprinter," said Halvorsen in a team press release. "My impression is that the team has a good environment and a culture that will suit me. This feels like the right choice to help me achieve my goals as a cyclist.
"I'm a sprinter that really, really likes to win and hates to lose. I want to help us win together as a team, help us develop as a team."
New signings of young riders are usually accompanied by talk of growth and steady progression, but EF team CEO Jonathan Vaughters said that he believes Halvorsen is a future Monument winner, namely Milan-San Remo.
"Kristoffer is a great talent, and it's up to us now to help him realise that talent," he said. "Our sports science and sports director group is motivated to make this guy a champion.
"As an organisation, we're only missing one Monument on the trophy mantle, and that's Milan-San Remo. Halvorsen is our ticket to getting that last one over the fireplace."
Halvorsen is EF's fourth new signing for the future, with the team having brought in Luis Villalobos and Sergio Higuita mid-season. Jonas Rutsch (Lotto-KernHaus), Neilson Powless (Jumbo-Visma) and Magnus Cort Nielsen (Astana Pro Team) have already been confirmed for 2020, while double Tour de l'Avenir stage winner Stefan Bissegger will join next August.
Matti Breschel, who will retire and train as a directeur sportif, and UAE Team Emirates-bound Joe Dombrowski, are the two riders so far confirmed to leave the team at the end of the year.