Building a Legal Coworker with GPT-5

This post announces the integration of GPT-5 into the Harvey platform, highlighting its enhanced reasoning, tool use, and drafting capabilities. It details how GPT-5 enables more complex, multi-stage workflows that can branch, loop, and self-correct, moving Harvey towards an 'intelligent coworker' paradigm. The post quantifies GPT-5's performance improvement on the BigLaw Bench evaluation suite (5.09% over previous frontier models) and provides an example of an orchestrated agent task for regulatory gap analysis. It emphasizes the shift from prompt-based execution to project-based management and proactive collaboration, leveraging GPT-5's ability to transition between in-depth reasoning and high-throughput tasks.