China is tightening its border and exit rules starting mid-September, and the warning is blunt: tech workers, chip industry staff, and Taiwanese business people should stay away.

• New national exit-entry regulations kick in September 15, giving Beijing formal cover to block people from leaving.
• Taiwanese academic Yeh Yao-yuan says China was already grabbing people at will — writing it into law signals it will now happen on a large scale.
• Semiconductor and tech talent are seen as the most exposed group, along with Taiwanese business owners working on the mainland.
• AI and big-data surveillance means old online posts can now be traced back to individuals who once assumed nobody was watching.
• The advice offered to anyone weighing a trip: value your life, stay away from China.

Outlook: Expect more Taiwanese and foreign tech workers to cancel mainland travel once the rules take effect, adding friction to cross-strait business.