In a futuristic city, three robots—Alpha, Beta, and Gamma—made statements about who committed a minor software glitch. Alpha said: 'Beta did it.' Beta said: 'Gamma did it.' Gamma said: 'Beta is lying.' Exactly one robot is telling the truth. Who committed the glitch?

Beta

If Alpha is truthful, Beta did it, making Beta's statement false and Gamma's statement true (since Gamma says Beta is lying). This yields two truths, which violates the rule. If Gamma is truthful, Beta is lying (so Beta didn't do it) and Beta's statement ('Gamma did it') is false, making Alpha false too. This works: Gamma is the only truth-teller, meaning Beta did it (since Beta claimed Gamma did it, making Beta's statement false). Wait, if Beta did it, Alpha is telling the truth and Beta is lying. Let's check: if Beta did it, Alpha is true, Beta is false, Gamma is true. That's two truths. Let's re-evaluate: Only one truth. If Gamma is true, Beta lied. Beta said Gamma did it, so Gamma didn't do it. Alpha said Beta did it, which is false. So Alpha is false, Beta is false, Gamma is true. This means Beta did NOT do it. Who did? If Beta didn't do it, and Gamma didn't do it, then Alpha did it. Let's test Alpha: Alpha is false. Beta is false. Gamma is true. If Alpha did it, Alpha's statement 'Beta did it' is false. Beta's statement 'Gamma did it' is false. Gamma's statement 'Beta is lying' is true (since Beta's statement was false). Exactly one truth (Gamma). Thus Alpha did it.