WASHINGTON -- If the Mets’ acquisition of Francisco Lindor represented the beginning of a new, more extravagant era in Flushing, their subsequent contract negotiations provided something of a litmus test. Signing Lindor to a long-term extension would provide proof of a culture change under owner Steve Cohen. Not doing so, regardless of the reason, would evoke that familiar chorus -- “same old Mets.”

Late Wednesday evening, the eve of Opening Day, team officials sang boldly and clearly that these are not, in fact, the same old Mets. Making good on the implicit promises of Cohen’s ownership, the Mets agreed to an extension unlike any in franchise history, announcing the deal on Thursday afternoon when Lindor met with the media. The 10-year, $341 million deal will keep Lindor in Flushing until his 38th birthday, according to a source. It is the longest contract in Mets history, and nearly three times as lucrative as the team’s previous largest deal -- $138 million over eight years for David Wright.

The Mets expect Lindor to serve not only as a centerpiece of their roster, but as the face of their franchise and perhaps all of baseball.

"To the fans in New York, here we go baby," Lindor said. "Here we go."

In terms of numbers, Lindor’s deal is nearly unprecedented across the American sports landscape. The richest contract ever for a shortstop, Lindor’s deal is the third largest in Major League history behind only Mike Trout and Mookie Betts. Lindor’s $22.3 million salary for 2021 remains unchanged, making the Mets’ total commitment to him $363.3 million over 11 seasons. The contract includes a limited no-trade clause and zero opt-outs, according to a source, all but assuring Lindor will be a Met for the bulk of his career.

As Thursday's Opening Day neared, it appeared as if the agreement might never happen. Late in Spring Training, the Mets extended an offer worth around $300 million to Lindor, according to a person with knowledge of the negotiations. Lindor countered with a $385 million asking price, which Mets officials considered exorbitant. Still, over dinner in Florida last weekend, Cohen personally extended what he considered the team’s best and final offer: $325 million over 10 seasons. He then removed all deferred money from the deal, making it richer in real-world value than the 14-year, $340 million contract Fernando Tatis Jr. recently signed with the Padres.

Next came a days-long impasse in which neither side budged. With Lindor’s Opening Day deadline rapidly approaching, talks finally reopened late Wednesday.

When those discussions finished, the sides came away with a revamped deal that includes about $50 million in deferred money, according to a source. It allows Lindor to claim the richest contract in history for a shortstop, topping Tatis by $1 million.

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So ends one of the more public negotiation sessions in franchise history. Immediately after the Mets acquired Lindor and Carlos Carrasco in a six-player deal with the Indians in January, team president Sandy Alderson said the Mets made the trade with an eye toward extending Lindor, while still acknowledging the possibility that the sides might not come to an agreement. He did not open negotiations with Lindor until March, and he kept things relatively casual until late in the month.

All the while, Lindor spoke frequently about his infatuation with the franchise and the city of New York.

“It’s a city with a lot of opportunities to grow,” Lindor said recently in a telephone interview. “The Mets are a team that a lot of people are excited about. The people are ready to see them win.”

Lindor is now a driving force behind that pursuit, both in the short- and long-term future. A four-time All-Star and two-time Gold Glover, Lindor owns a career .285 average with 138 home runs and 99 stolen bases over six seasons. He is a switch-hitter slated to bat second in New York’s lineup this season, providing the type of dynamic unseen in Flushing in years.

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Lindor’s teammates, understandably, were elated by the news when it broke late Wednesday night. “Can’t sleep,” tweeted catcher James McCann, who competed against Lindor in the American League Central before joining him at Mets camp this spring. “We bouta have a fun year!!” said pitcher Taijuan Walker, who hinted at the Lindor news mere minutes before it broke.

Across the tri-state area and beyond, the Mets’ fan base reacted in similar ways, overjoyed at the commitment -- not just from Lindor, one of the best players in baseball, but from the team itself: the “same old Mets” no longer.