Caffeine plus L-theanine is the nootropic pairing closest to consensus, sold as caffeine's focus without the jitters. But does the combination really improve attention, and how much of that is the theanine? This piece works through the controlled evidence and the meta-analyses, which do support a modest attention benefit in the first hour or two, and then delivers the nuance the marketing skips: most of the benefit comes from the caffeine, theanine alone does little for cognition and can even blunt caffeine at some doses, and its real job is smoothing caffeine's arousal so the focus feels steadier. Useful, then, but for the right reason.