"This makes public how we've been operating," said Beane, after concluding his 18th season as GM. "David has a lot of autonomy, he had it before, and he'll continue to have that.
"His confidence and his skillset should be rewarded, as should his loyalty."
Forst, 39, just completed his 16th season with the A's, the last 12 coming as assistant general manager. In the last decade, he's procured a handful of opportunities to interview with several Major League clubs for the GM job -- a total so high, Beane said, "We've stopped counting."
Each time, his right-hand man has opted to stay.
"Billy brought me in and, from Day 1, included me in everything, and every opportunity that has come up, it always came back to the fact I wanted to be here," Forst said. "That's what I've always wanted, and my family loves it here. I'm thrilled to have this happen and to know I'm going to be here for a while."
"Quite frankly," Beane said, "he's one of the most valuable people in the organization."
The announcement came less than 24 hours after one of the more miserable seasons in recent A's history came to a close. Their 68-94 record, lowest in the American League, was the club's worst mark since 1993.
But in Beane's previous 17 seasons, the 53-year-old built six division winners and eight postseason teams despite payroll constraints.
"Billy Beane and David Forst have continually proven themselves to be two of the best baseball minds in the game today," A's owner and managing partner Lew Wolff said in a statement. "The team remains in great hands. We're very fortunate to have not one but two executives of their caliber."
Under his new label -- reflective of the increasingly popular dual executive model employed by several clubs, including the Cubs, Red Sox and Dodgers -- Beane mentioned he hopes to have more time to be involved in the workings of the grassroots of the business: traditional amateur scouting.
The A's will pick sixth in the 2016 MLB Draft, their highest selection since 1998.
"After a while," Beane said, "you get separated from that part of it and like to reconnect with it in a bigger way, so I'm hoping that's the case."
Before Monday, Forst shared the assistant general manager position with another GM-in-the-making, Dan Kantrovitz, whose role remains the same. Beane hinted another hiring could eventually be made, though it's not a priority.