A custom 32-bit CPU encrypted at gate-level with anti-tamper and anti-debug protections went unsolved for a year by humans and multiple LLMs, until GPT-6 solved it in 20-30 minutes using side-channel cryptanalysis to exploit weak encryption protecting the CPU state. The challenge featured a virtual architecture with 16 general-purpose registers, bit-addressable memory, and obfuscated VHDL synthesis.