r/AI_Agents: Static System Prompts Are the Wrong Architecture — Making LLM Context Assembly Programmable Outperforms Fixed Concatenation for Long-Running Agents

An agent developer argues on r/AI_Agents that treating the system prompt as a static file read at startup is architecturally wrong for production agents, citing lost-in-the-middle research showing instruction position materially affects model compliance. The post proposes making context assembly programmable — dynamically injecting relevant rules, skills, and context based on task type rather than concatenating everything at session start. Practitioners in the thread confirm the same degradation pattern in production: static large system prompts combined with long tool-call histories cause agents to silently drop instructions mid-session.