PrivacyLib: Privacy Controls at the Data Access Boundary

Meta details PrivacyLib, a common library embedded in the clients of hundreds of its data and processing systems that enforces privacy requirements at the point of data access, performing billions of checks per second. Systems integrate once and new requirements arrive as plug-in modules, with changes simulated before release and rolled out per module; for internal AI agents, tool calls carry agent context to PrivacyLib so modules can observe data use and block disallowed operations.