Large-language-model “memories” can enhance user experience but also increase vulnerability to memory injection attacks.Memory injection attacks can occur through Interaction-Only Write, Dormant Persistence, and Cross-User Contamination patterns.Defense playbook includes hardening inputs at the edge, compartmentalizing memory, and implementing a runtime anomaly guardrail.Operational checklist involves edge filtering, per-tenant memory management, guardrail implementation, audit jobs, and red-team rotations.