I’ve never felt comfortable with how people use Claude Code or Codex as synonyms for Harness. It’s not wrong, it just reduces the harness to the least interesting part: the runtime. It’s the part you have the least control over. Most of us use what ever subscription makes most sense or whatever our company has settled on.

To me the interesting part of the harness is what you add on top, Brigitte Böckeler calls it the outer harness. I prefer the term Your Harness, your harness breaks down into two things: Skills and Loops.

Skills change what the agent knows and the loop changes how it works and checks itself. Both can mostly be encoded in Agent Skills

Your Harness should mostly agnostic to the agent you use.