Defense in depth

Layer protections so no single failure is catastrophic:

• Edge hardening: security headers, CORS locked to known origins, and rate limiting per route class (auth, chat, upload) to blunt abuse and brute-forcing before requests even reach a handler.
• Input validation: validate request shapes explicitly; never trust client-supplied JSON, ids, or model selections.
• Auth + authorization: as above.
• Encryption: secrets at rest, TLS in transit.
• Least-privilege tools: the model's blast radius is bounded by its tools.
• Audit trail: the versioned, sourced records (Chapter 9) double as a security log of who/what changed each artifact.

No layer is sufficient alone; together they make the system resilient.