Heat oven to 350°F. Line a 9×13-inch pan with parchment, leaving an overhang.
Stir graham crumbs, brown sugar, and fine salt in a bowl. Pour in melted butter and mix until evenly moistened.
Press the mixture firmly into the pan. Bake 8–10 minutes, until the edges look set.
Scatter chopped pecans over the hot crust and set the pan aside.
Melt caramels with heavy cream in a saucepan over low heat, stirring until smooth. Remove from heat and stir in vanilla.
Pour warm caramel evenly over the pecans and crust. Spread to the corners.
Bake 10–12 minutes, until the caramel is bubbling at the edges.
Sprinkle chocolate chips over the hot pan. Let sit 3 minutes, then spread into a smooth layer.
Finish with flaky sea salt and sprinkles, if using. Cool completely, then chill 30 minutes to set before slicing.