OpenAI GPT-5 outperforms o3 with 83% correctness, and Glean customers can put it to work today

This post details Glean's evaluation and integration of OpenAI's GPT-5 model into its agent orchestration platform. It presents comparative metrics showing GPT-5's outperformance over o3 in correctness (83% vs. unknown), completeness, and alignment with human feedback. The analysis highlights GPT-5's broad tool usage and parallel tool calling capabilities as key differentiators, leading to shorter planning steps compared to o3's deep, stepwise approach. The post also discusses GPT-5's improved ability to gauge when to ask follow-up questions and introduces verbosity controls for response length, along with observations on improved formatting quality. The evaluation was conducted using Glean's internal LLM judges and production deployment.