Hydrogen embrittlement remains one of the most critical challenges to the safe and reliable use of metallic materials in hydrogen-based energy systems. Its complexity arises from the interplay of multiple microscopic mechanisms, such as hydrogen-enhanced localized plasticity (HELP), adsorption-induced dislocation emission (AIDE), hydrogen-enhanced strain-induced vacancy formation (HESIV), and hydrogen-enhanced decohesion (HEDE). The competition between these mechanisms governs whether fracture occurs through decohesion-driven intergranular failure or through microvoid coalescence leading to transgranular fracture. This work presents a continuum mechanics-based numerical framework, implemented within the finite element method, to predict fracture and identify the governing fracture regime in high-strength steels exposed to pressurized gaseous hydrogen. The elastoplastic constitutive behaviour is described using a yield function based on the one proposed by Gao et al. , in which the equivalent stress scalar depends on the stress invariants I1, J2, and J3. This formulation is coupled to a modified Gurson-type continuum damage model capable of representing both microvoid-coalescence-driven and decohesion-driven fracture. The mechanical formulation is further coupled with a hydrogen diffusion model to compute the spatial distribution of hydrogen concentration. Hydrogen transport is influenced by the local stress state, while the elastoplastic response and damage evolution are, in turn, dependent on hydrogen concentration, enabling a fully coupled description of hydrogen-assisted fracture. Finally, the predictive capability of the framework is demonstrated through parameter calibration against experimental data for high-strength steels tested in air and in pressurized hydrogen environments, showing that the model successfully captures hydrogen embrittlement-driven fracture behaviour.