Most companies deploying AI agents hit the same wall about two months in: the agent forgets everything between sessions, can’t read the company’s actual knowledge (strategy docs, pricing logic, customer notes), and has no clean way to write what it learns back to the team’s knowledge base for human review. The toolkit for solving this is strong, but the question that matters for a mid-market team is different from the question developers ask. It isn’t “which API surface is cleanest.” It’s “how does a company actually maintain its knowledge, feed it to agents, let agents add to it, and keep humans in the loop?” As of April 2026, there are five named systems worth comparing (Mem0, Zep, Letta, Cognee, and Cloudflare Agent Memory) plus a sixth path: maintaining knowledge as plain markdown and giving agents read/write access through a semantic search index.…