How to Add Persistent Memory to Any AI Agent (Step-by-Step)

Your agent works perfectly on day one. By day three, it's asking the same questions it already answered. By week two, it contradicts decisions it made last Tuesday. The problem isn't your prompts. It's that your agent has no memory that survives a restart. This tutorial shows you how to add persistent memory to any AI agent — Claude, GPT, open-source, whatever you're running — using a simple REST API. Three endpoints. Under 10 minutes. The Problem: Agents Are Stateless by Default Every major agent framework starts each session from zero. Your agent gets a system prompt, maybe some recent context, and that's it. Everything it learned yesterday? Gone. The typical workarounds fail at scale: Stuffing context windows: Works until your agent's knowledge exceeds 100K tokens. Then you're paying $0.30+ per call and still losing older context. Local files: Works for single-agent setups. Falls apart with multiple agents, concurrent sessions, or any deployment that isn't your laptop. Vector databa