When iPhone engineer Chang Liu quit for a job at OpenAI’s nascent hardware division, Apple Inc. says he left with more than just years of experience.

According to a lawsuit filed Friday, Liu departed with three things: a company-issued MacBook he never returned, a close relationship with an Apple employee who continued sharing internal information, and, most significantly, knowledge of a software bug that gave him ongoing access to internal file servers.

“LOL, I found out I can access the [network storage], so funny,” Liu wrote to his former Apple colleague, Alyssa Peng. He then, Apple alleges, used that access to download presentations, hardware designs, manufacturing details and testing procedures — all while already working at OpenAI.

When Liu discovered the bug, Peng stepped in to help, according to the suit. She replied, “I’m ready,” and eventually helped obtain more information through her own laptop. A few months later, in April, Peng herself left for OpenAI’s growing hardware division.

She joined more than 400 other former Apple employees drawn by the opportunity to work on next-generation devices designed to replace the two-decade-old iPhone — with salaries and stock options that trumped Apple’s less dazzling pay packages.