AI in Practice, No Fluff — Day 6/10 I spent weeks refining a system prompt. It had few-shot examples, chain-of-thought scaffolding, structured output formatting. In the ChatGPT window, it was reliable. Exactly the tone and format I wanted, every time. Then I copied it into my application code, hit send through the API, and the response was wrong. The formatting was off, the tone reverted to generic, and the structured JSON I had been getting reliably came back wrapped in a conversational preamble. I didn't change the prompt. So what happened? This is the moment you realize that the chat interface was silently helping in the background... The invisible work When you use ChatGPT, Claude.ai, or Gemini through their web interface, you are not just sending a prompt to a model. You are using an application that sits between you and the model, and that application is doing more work than you would expect. System prompts you did not write. Every chat interface injects its own system prompt before yours.…