L-Theanine and Vitamin B12 sit under two different mechanism fronts in this formula — focus and mental energy — worth understanding how they complement rather than duplicate each other.
L-Theanine is described as promoting calm, focused attention, while Vitamin B12 is described as supporting healthy nervous-system function and brain energy — a calm-without-drowsy, energised-without-jittery combination, per this site's own framing.
This specific pairing is worth reading as central to how this site achieves alertness without stimulants — L-Theanine's calm and B12's energy together, rather than caffeine's more one-dimensional stimulant effect.