Solution graph eq54: u_xx u_yy - u_xy^2 = f(x,y) (Монж–Ампер; Тестовая задача 13)

The graph reads left to right. Problem — the original equation. Idea — a solution plan the agent formulated before trying. Variant — an attempt to solve along the idea; a successful variant ends in a ★ final solution. A variant is carried out by an implementation: subtasks whose solutions (fragments) are assembled into the final solution — only some fragments make it into the result. A dead end is a variant that produced no solution: its whole branch (implementation, subtasks, fragments) is not part of the result. Completeness is a separate branch: the argument that there are no other solutions.