The loop-tree duality (LTD) has become a novelty
alternative to bootstrap the numerical evaluation of
multi-loop scattering amplitudes.
It has indeed been found that Feynman integrands,
after the application of LTD, display a representation
containing only physical information, the so-called causal representation.
In this talk, we discuss the all-loop causal representation
of multi-loop Feynman integrands, recently found in terms
of features that describe a loop topology, vertices and edges.
Likewise, in order to elucidate the numerical stability
in LTD integrands, we present applications that
involve numerical evaluations of
two-loop planar and non-planar triangles
with presence of several kinematic invariants.