Watching 'Jujutsu Kaisen', I got obsessed with trying to pin down exactly what the Six Eyes can and can't do, and the more I read the manga and rewatch the anime, the more I think of it as a supercharged sensory processor rather than an all-powerful eye of god.
Canonically, the Six Eyes massively reduces cursed energy consumption and gives ridiculously precise perception of cursed energy and techniques. That’s why Gojo can layer complex uses of Limitless and Reversed Cursed Technique with almost no stamina cost — his brain literally sees and calculates the smallest fluctuations, so he doesn’t waste energy on guesses. Practically, it means near-instant reaction, perfect spatial awareness, and the ability to understand and replicate certain flows of cursed technique just by observing. However, it doesn’t override physical laws: if you’re sealed (hello, Prison Realm) or hit by a technique that bypasses visual perception or messes with causality, Six Eyes can’t save you. It’s also tied to line-of-sight and the presence of perceivable cursed energy. Invisible or completely sealed techniques, special kinds of binding or domain tricks engineered against him, or removing his eyes render it useless.
So the limits are straightforward: dependency on ocular input, vulnerability to seals and counter-techniques, and no true omniscience — he still can be surprised, trapped, or incapacitated. I love that; it keeps him thrilling instead of unbeatable, and it makes confrontations in the series feel tense rather than scripted in his favor.