The Patriots have locked up Pro Bowl tight end Rob Gronkowski for a long time. The sides agreed to what amounts to an eight-year deal with a maximum value of $55.1 million, a league source said.

That means Gronkowski is signed through the 2019 season -- in theory.

A source originally said Friday morning that the two sides were working on an extension, but that nothing was final yet.

Gronkowski still has two years remaining on the four-year contract he signed as a rookie in 2010, and NFL Network’s Albert Breer reported that while the tight end won’t receive a bump in base salary for 2012 and ‘13, he will get new money in the form of an $8 million signing bonus now.

The details of the contract are still confusing, but his agent. Drew Rosenhaus, celebrated the deal on Twitter. He said, “Congrats to Gronk & his family on his contract extension with the Patriots. My thanks to Mr.Kraft & Coach Belichick for making this possible.”

ProFootballTalk.com reported that in 2016 there’s a $10 million option bonus, and the Patriots will have to decide whether or not to pick that up. If they do, Gronkowski’s salary in 2018 will be $8 million and in 2019 it will be $9 million.

As PFT noted, it looks like the deal is for three years, $13.23 million at a minimum -- about what Brandon Lloyd got from New England -- and if Gronkowski isn’t cut after three years, it’s $18.23 million over four years.