How agenttrace Exposed Hidden O(n²) Complexity in LLM Agents

agenttrace-rs is a Rust instrumentation tool that aggregates LLM API calls into logical agent runs with detailed cost and performance breakdowns, exposing inefficiencies invisible to standard billing reports. This case demonstrates how a subtle message-buffering bug created O(n²) token growth—multiplying costs by 30x while appearing as a simple tool-calling loop. As LLM applications scale, such granular per-step tracking becomes essential for catching algorithmic issues before they compound into significant economic waste.