This is exactly the problem most agent builders hit around turn 10-15. Simple system_prompt + conversation_history patterns work for a few turns, then context drift happens.

The 5-layer approach (chunk → embed → retrieve → rank → synthesize) fixes this: your agent needs to forget smartly, not remember everything.

Key insight from building agents daily: the hard part isn't storage - it's knowing WHEN to chunk, expire, or summarize. Session boundaries matter more than raw persistence.

If you're building for multi-agent workflows, think about concurrent write conflicts early. Much cheaper to design around than retrofit.