Google Deploys a Dual-Loop LLM Agent System on YouTube That Autonomously Found RMSprop, Gated Path, and a Multi-Objective Reward, Lifting Multiple A/B Metrics
The work proposes and deploys a self-evolving recommendation system in which Gemini-family LLM agents act as machine learning engineers: an Offline Agent (Fast Loop, waking every 5 minutes and running daily) generates and offline-scores candidate configurations, while an Online Agent (Slow Loop, running daily) ranks candidates and drives A/B experiments; across several YouTube recommendation surfaces the agents autonomously discovered optimizer switches (Adagrad to RMSprop, FTRL), a Gated Path (GLU) architecture, activation refinement, multi-objective reward synthesis, and reward hyperparameter tuning, with multiple online metrics improving at the 95% confidence level and experiment throughput rising from Θ(1)-Θ(10) per week to Θ(100) per week.