New workflow control method for harness engineering — Signature-Based Locking

The Problem: AI Won't Stay Harnessed If you've been building AI-assisted development workflows — what some call "harness engineering" — you've hit this wall: No matter how carefully you craft your prompts, the AI eventually goes off-script. You define a multi-step workflow. The AI follows it for a while. Then somewhere around step 4, it decides to "optimize" by skipping steps, modifying files directly, or inventing a shortcut that breaks your entire pipeline. This isn't a prompting failure. It's a fundamental limitation of prompt-only workflow control. Why Prompt-Only Control Fails Three documented forces work against prompt-based workflow enforcement: 1. Context Rot (Lost in the Middle) As conversations grow longer, instructions from the beginning of the context window lose influence. Research published in TACL ("Lost in the Middle") demonstrates that LLMs exhibit a U-shaped attention curve — they attend strongly to the beginning and end of context, but performance degrades by over 20