r/ChatGPT: Reverse-Engineering AI Dev Tool Harnesses Reveals Every Input Passes Through Complex Stateful Middleware Before Reaching the Model

A developer post dissecting the orchestration layers inside AI coding tools argues that developers operate under a 'scaffolding illusion' — every input to Claude Code, Cursor, Codex, and similar tools is intercepted and augmented by complex stateful middleware before reaching the underlying model. The analysis maps how system prompt injection, context augmentation, tool execution policies, and memory management layers each shape model behavior independently of the raw model weights, with significant variation across tools in how much middleware is exposed to users. Community discussion focuses on whether harness transparency has become more important than model selection for production agentic workflows.