One of Broadway’s juiciest, longest-running feuds may have just ended.

Andrew Lloyd Webber and Patti LuPone haven’t spoken to each other since the composer fired the diva from “Sunset Boulevard” in 1994.

But on Thursday, at the old Hit Factory on West 54th Street, they met to rehearse “Don’t Cry for Me Argentina,” which LuPone will sing Sunday night at the Grammy Awards.

Lloyd Webber arrived first. LuPone swept in a few minutes later. Witnesses held their breaths as she picked up a microphone.

“Hello, Andrew,” she said and then, turning to the others in the room, added, “This is détente, ladies and gentlemen.”

There were big laughs, Lloyd Webber and LuPone embraced — and went to work.

The Grammy telecast is giving a nod to Broadway with a salute to Lloyd Webber and Leonard Bernstein, who would have been 100 this year. Ben Platt, who won a Tony for “Dear Evan Hansen,” will perform a medley of Bernstein songs.

LuPone, Broadway’s original “Evita,” readily agreed to sing the show’s biggest song, which, because of the show’s time constraints, needed to be cut by one minute.

Sources say LuPone insisted that Lloyd Webber do the trimming. Then she brought down the rehearsal studio by singing the song in its original key.

“She’s in spectacular voice,” a source says. “Andrew was blown away.”

LuPone congratulated Lloyd Webber on Wednesday’s 30th anniversary of “The Phantom of the Opera,” and they chatted privately for a few minutes. Sources say Lloyd Webber made her laugh when he suggested it was time for an “Evita” revival. (Ricky Martin starred in one in 2012.)

And so détente it appears to be.

The “Sunset Boulevard” saga is legendary. (It certainly made for a juicy chapter in LuPone’s memoir a few years ago.) Lloyd Webber cast LuPone as Norma Desmond in the London production in 1993. She had it in her contract that she would open the show on Broadway the next year. But Glenn Close opened the show in Los Angeles, got rave reviews and wound up with the Broadway production.

Wounded, LuPone sued and won what was reportedly a $1 million settlement from Lloyd Webber. As she writes in her memoir, she used the money to put in a pool on her property in Connecticut.

She called it “The Andrew Lloyd Webber Memorial Pool.”

The feud flared up again last year when LuPone knocked the composer during an interview with New York 1’s “On Stage.”

Knowing LuPone and Lloyd Webber would meet again had everyone at Wednesday night’s “Phantom” party recalling that feud.

“It’s time to move on,” a Lloyd Webber associate told me. “Andrew has.”

Broadway fans will be on the edge of their couches Sunday night, waiting for the “Don’t Cry for Me Argentina” moment. It comes in the 10 o’clock hour.

The “Phantom” 30th was a terrific bash, by the way. The show is in great shape. Sarah Brightman, the original Christine, appeared during the curtain call and, proving her pipes are still golden, drew a standing ovation singing the title song.

To top it off, there was a “Phantom” light show on the Empire State Building, which revelers watched from the Rainbow Room atop Rockefeller Center, while a “Phantom” medley, synchronized to perfection to the light show, swept the room.

So a big happy 30th to Broadway’s longest-running show.