Man, Dumbledore and Horcruxes—now that’s a rabbit hole worth diving into. From the moment he met Tom Riddle at Wool’s Orphanage, I think he had suspicions. Riddle was too fascinated by power, too obsessed with immortality, and Dumbledore wasn’t fooled by his charm. By the time Harry came into the picture, Dumbledore was already piecing things together. The diary in 'Chamber of Secrets' was a huge clue; it screamed 'Horcrux' to someone as knowledgeable as him. Then there’s how he reacted to the ring in 'Half-Blood Prince'—he destroyed it immediately, knowing exactly what it was.
But here’s the thing: did he know everything? Probably not. He didn’t realize there were multiple Horcruxes until later, and even then, he had to guess how many. His research with Harry in the Pensieve shows he was still figuring it out. Dumbledore was brilliant, but even he had to play detective with Voldemort’s twisted mind games. In the end, his hunches were right, but it wasn’t some all-knowing wizard thing—just decades of watching Riddle’s patterns.