The Boston Celtics have found a solution to their most urgent off-season question. Jaylen Brown will remain with the team for the foreseeable future.

The Celtics’ winger has agreed to a five-year supermax deal extension worth up to $304 million, according to his agent.

It is the costliest contract in NBA history, surpassing Nuggets center Nikola Jokic’s US$264-million deal signed last summer.

The agreement was initially reported by ESPN and confirmed by Brown’s agent, Jason Glushon, to the Associated Press.

Brown will remain with the team that chose him third overall in 2016 and saw him blossom into a two-time All-Star.

Last season, he set career highs with 26.6 points, 6.9 rebounds, and 3.5 assists. However, those figures dropped during the playoffs, when the Celtics were defeated in the Eastern Conference finals by the Miami Heat. Brown scored 19 points on 8-of-23 shooting in Game 7, completing only one of nine 3-point tries.

Nonetheless, his experience in Boston has made him a critical member of the team’s current core, which management was unwilling to risk losing when his current four-year contract expires after next season.

Brown was eligible for the supermax extension since he was named to the All-NBA second team, his first such honor in his career.

Since the end of the previous season, Celtics president of basketball operations Brad Stevens has been adamant that Brown sign a long-term contract.

“He’s a major part of who we are. “We believe in him, and I appreciate him,” Stevens remarked last month. “I’m grateful that when those guys succeed, they come back to work.” And when they are beaten, they own it and return to work. So I know what they’re all about. And that is difficult to come by.”

All-Star Jayson Tatum, who has teamed with Brown to lead the Celtics’ one-two punch to the NBA Finals in 2021-22 and the conference finals last season, echoed those comments.

Tatum stated after Boston’s East finals loss in May that keeping Brown long term was “extremely important.”

“He’s one of the best players in this league,” said Tatum. “He plays both ends of the field and is still quite young.” And he’s accomplished a lot in his career so far. As a result, I believe it is critical.”

Brown’s new contract will almost certainly result in some financial maneuvering down the road, as the league’s new Collective Bargaining Agreement places tighter restrictions on how teams form their rosters and imposes higher luxury tax penalties.

Tatum is still playing under the terms of his rookie contract, which began last season, and will be eligible for a potential supermax extension next summer.