alt Hacker News> harness ... a privilege boundary around the agent
They don't really do that though. If you want something sandboxed you actually have to sandbox it, not plead with the LLM to please sandbox itself. A VM can be configured to do the former, harnesses do the latter.
If you say in your CLAUDE.MD that a certain directory is read only inputs, Claude Code will actually enforce that and deny any write to that directory by the agent. To name just one example.