I read elsewhere that this deal has been in the works since the Super Bowl.
Also, Mike Florio claims to have the contract numbers here:
https://profootballtalk.nbcsports.co...-buckner-deal/
If this is true, then it's a five-year deal (I've heard it referenced as a four-year extension elsewhere - presumably in recognition of the fact that he was already under contract for next year prior to the trade). And it looks like the real guarantees are all in the first three years.
By the way, what's with this Mike Florio guy? I think he sucks. Seems to be a Patriot apologist, and always subtly putting down the Colts. After reading the article, you might come away with the impression that Buckner was a leftover player that the 49ers no longer wanted or needed following the Armstead signing - yet the idiot Colts were willing to spend a 1st and sign him to a mega contract.