Apparatus and methods are provided for adaptation handling for L2-based sidelink relay for packet routing. In novel aspect, the sidelink adaptation protocol (SAP) layer inserts SAP header including the adaptation layer address (ALA) before routing the packet data to the next hop. In other embodiments, the SAP layer includes a sequence number (SN). In one embodiment, the SN number in the SAP layer is the same as the PDCP SN number. In another embodiment, the SAP layer assigns SN number. In other embodiments, the SAP layer performs bearer mapping between an ingress logical channel and an egress logical channel at one or more intermediate nodes. In one embodiment, the bearer mapping is based on the QoS information or is based on a fixed logical channel configuration.