Why do AI companion apps still can't maintain persistent memory? (technical discussion)

I've been researching AI companion apps from both a user and technical perspective, and the memory problem fascinates me. Character. AI has 20M+ monthly users and still can't reliably remember a user's name across sessions. Even apps that claim "long-term memory" usually just stuff a summary into the system prompt. From what I can tell, the core issue is architectural: **Why current approaches fail:** - **Context window stuffing**: Most apps just inject a summary blob into the system prompt. This compresses weeks of nuanced interaction into a few paragraphs.