Why context windows keep breaking AI agents (and how knowledge graphs fix it)

Last week, an agent in a coding workflow looked perfectly fine for the first 20 minutes. It knew the repo structure. It remembered the ticket. It even used the right MCP tools to inspect files and open a PR. Then the session got longer. A few tool calls. logs. intermediate reasoning. pasted docs. And suddenly the agent started acting like a teammate who joined the meeting halfway through: repeating work, forgetting constraints, and asking for data it had already seen. That’s the part nobody tells you about “long-running” AI agents: they don’t really have memory.