Article 18 governs internal contribution among jointly liable economic operators + the right of recourse: this Directive shall be without prejudice to provisions of national law concerning the right of contribution + recourse among liable economic operators. The Article 18 framework + Article 14 joint-and-several liability creates a two-step regime: (1) injured person sues any one liable operator under Article 14; (2) defendants resolve the relative shares among themselves under national contribution + recourse rules. The Article 8 chain-of-recourse rules supplement Article 18 by mandating that each economic operator has a right to be indemnified by the upstream operator for the relevant portion of liability.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.