You both should just read the docs

https://docs.darkbloom.dev/security/overview

They lay out all the protections they have in place to ensure private prompt execution. The TEE is used to validate the integrity of the binary, and they use other protections like E2EE, SEV-SNP on the coordinator, MacOS security protections (hardened runtime, SIP, kernel protections, etc), plus (from what i can tell an optional enrollment from providers) in Apple's MDM which makes Apple verify the integrity of the system.