Abstract: A vehicle seat includes a seatback having a support structure with a rigid frame member that extends within a side of the support structure. A side airbag assembly includes an airbag coupled with the frame member. First and second trim pieces engaged along a seam to conceal the airbag. A flange protrudes along an edge of the first trim piece and a cavity extends along the second trim piece to matably engage the flange. A retention slot is disposed on a wall of the cavity and an attachment element protrudes adjacent to the flange to frictionally engaging the retention slot. The attachment element is configured to disengage from the retention slot upon deployment of the airbag forward through the seam.