Signal president Meredith Whittaker warned that agentic AI features pose an 'existential threat' to end‑to‑end secure messaging and the app ecosystem that depends on it. Whittaker told Fortune that agents need access to vast private data to act on users’ behalf, creating attack surfaces for prompt‑injection and data exfiltration that could nullify app‑level encryption guarantees. The comments target OS‑level integrations being pushed by major tech platforms and underscore a widening debate about privacy, platform architecture and university reliance on secure communications for research, journalism and student safety.