CM fibers of Shimura parametrizations and thirteen proofs of the class number one theorem

We determine thirteen entirely CM identity fibers of Shimura parametrizations attached to elliptic curves of rank two and conductor below $2000$. Each yields a proof of the imaginary quadratic class number one theorem. The argument combines the Gross–Zagier formula with the Ribet–Takahashi degree comparison to show that the fiber is completely explained by known CM points.