TL;DR Anthropic shows that the real challenge for AI agents is not starting a task, but staying coherent throughout long executions. Avoiding cognitive drift requires a runtime harness built on external memory, checkpoints, and continuous re-anchoring. The next frontier is not autonomy alone: it is cognitive continuity. Anthropic and the Runtime Harness: the Real Problem with Agents Is Not Acting, but Not Getting Lost While They Act If the OpenAI case showed how a repository can be rethought to become readable for agents, the contribution published by Anthropic in Harness design for long-running application development opens an even more delicate question: what happens when the challenge is no longer how to start a task well, but how to keep it alive for hours? Because this is where many agentic systems truly begin to break.…