What Is a Harness? Why the Same Model Behaves Differently Across Coding Agents
The article explains why swapping the Harness — the runtime environment around an AI model — changes agent behavior even when the model weights stay identical, covering system prompts, tool definitions, agentic loops, translation layers, execution boundaries, feedback fidelity, context compression vs. immutable event logs, and architectural trade-offs illustrated by Pi, Codex, DSH, and the claudex experiment.
