Multi-agent pathfinding problems involve finding plans for agents that must travel from their start locations to their targets without colliding. Recent work produced a number of algorithms to solve the problem as well as an ample supply of related theory. Most existing works, however, were either too inefficient for practical use or had very restrictive conditions. This work proposes a novel approach to solving Multi-agent pathfinding problems, based on tree decompositions, called Tree-based Agent Swapping Strategy (TASS). Using TASS we can guarantee that a problem will be solved in...