Comment by simonw

Claude Code is definitely a harness. The term harness is pretty loosely defined, but it effectively means the software that wraps an LLM, asks the LLM what tools it should execute, then executes those tools.

I wouldn't classify Claude Code as a sandbox, though it does have some sandbox features built in, using https://github.com/anthropic-experimental/sandbox-runtime (which I would classify as a sandbox)