  We formulate the first-order dissipative anisotropic hydrodynamical theory
for a relativistic conformal uncharged fluid, which generalizes the
Bemfica-Disconzi-Noronha-Kovtun first-order viscous fluid framework. Our
approach maintains causal behavior in the nonlinear regime with or without
general relativity coupling, and we derive and analyze the constraints on
transport coefficients imposed by causality. We demonstrate the causal and
stable behavior of our theory in specific cases, including the discussion of
nonlinear causality as well as stability for linearized perturbations. We apply
our newly developed first-order anisotropic theory to the Bjorken flow and show
how causality and stability impose constraints on the behavior of the
early-time attractor.
