Spotted by a fellow Brand Eater, Jack in the Box is calling it the Chick-N-Tater Melt.
The sandwich looks like it's a crispy value chicken patty with a hash brown patty, Swiss (or more likely, Swiss-style) cheese, bacon, cheese sauce, and ranch on a croissant.
Like the rest of Jack's Late Night Munchie menu, it's available in a combo with "halfsie" fries, two tacos, and a drink for $6.
At the test locations, it replaces the similar Exploding Cheesy Chicken Sandwich.
The test sandwich was spotted in both Santa Clara and San Jose.
Photos by Richard G.