Basis of the transaction or impossibility

One long-term contract, one shock. On the left, § 313: interference with the basis of the transaction, the right to demand adaptation, withdrawal or termination if adaptation is out. On the right, § 275: the claim to performance is excluded so far as performance is impossible; the counter-performance follows § 326. The model does not adapt the contract; it opens the right to demand adaptation. Whether adherence to the unchanged contract cannot be required is for the court. The page does not claim that § 275 ranks above § 313.