Methods for incorporating magnetohydrodynamic equilibria and internal instabilities into tokamak transport codes are reviewed with emphasis on how the models may be extended to reactor plasmas. Instabilities are characterized from a computational view as being either intermittent or continuous modes. Intermittent disturbances are treated adiabatically whereas saturated instabilities can be handled through enhanced transport coefficients. The m = 1/n = 1 mode serves as an example of how the character of an instability can change as we proceed from low-beta resistive plasmas to high-beta collisionless plasmas. The implications for reactor thermal dynamics of finite-beta-induced transport are discussed in terms of Impurity Studies Experiment-B observations and analysis.