When AI Leaks Internal Tags: Debugging a 3-Layer Streaming Architecture Bug

As an SDET testing AI applications, I recently encountered a bizarre issue in the OpenClaw Gateway UI. Instead of normal conversational text, the AI assistant started spitting out raw internal directive tags like [[reply_to:< and [[reply directly into the chat interface. These tags are designed for internal message routing and should be silently stripped by the system before reaching the user. At first glance, it looked like a simple "dumb LLM" problem. But diving deeper, I uncovered a fascinating architectural trap: a perfect storm of three distinct bugs across the backend stream, the UI state logic, and the defense-in-depth strategy. Here is how I debugged and fixed this cascading failure. The Investigation: Hunting the Leak Round 1: The Code Check My first instinct was to check the stripping logic. The backend used a standard Regex REPLY_TAG_RE to find and remove fully closed tags like [[reply_to:123]]. I wrote a quick test script, and the Regex worked perfectly on complete tags.