When System Prompts Become Prompt Debt -What GitHub Copilot’s hidden instructions reveal about AI agent design

I Read the System Prompt Most discussions about coding agents focus on model quality. I decided to inspect something else: the system prompt. What I found was not a short hidden prompt, but a large prompt program implemented in TypeScript (AgentPrompt.tsx), with conditional rendering, tool routing, memory instructions, safety rules, behavioral policies, and identity constraints. It is sophisticated. It also reveals a deeper design tension. I would call it prompt debt. Prompt Debt We know technical debt.