The Model Is the Brain. The Harness Is the Body. Here's Why That Matters

TL;DR: I built the same browser agent twice — once with 500 lines of Python, once with 7 lines of JSON. The second one took 5 minutes. The agent harness layer is becoming the real competitive advantage, not the model. Last month, I built a browser automation agent. Playwright. Custom orchestration. Login handlers. Error retries. Session management. React-aware form filling. Anti-detection scripts. 500+ lines of Python. This week, I built the same thing: { "model" : { "provider" : "bedrock" , "mo