The Giants signed Porter to a minor-league contract with an invitation to spring training Tuesday, Ari Alexander of KPRC 2 Houston reports.
Porter cleared waivers and was outrighted to Triple-A Syracuse by the Mets on Friday.
The Mets designated Porter for assignment Tuesday.
The Mets are in agreement with Porter on a major-league contract, Ari Alexander of KPRC 2 in Houston reports.
Porter has initiated the opt-out clause in his minor-league contract with the Giants, Ari Alexander of KPRC 2 in Houston reports.
The Giants acquired Porter from the Royals on Friday in exchange for cash considerations or a player to be named later.
Porter signed a minor-league contract with the Royals on Saturday.
Porter was designated for assignment by the Royals on Tuesday.
Porter isn't in the Royals' lineup Saturday versus Houston
Porter will start at catcher and bat eighth in Monday's game against the Guardians.