McKinsey Built a $1B Internal GPT Called 'Lilli' Trained on 70 Years of Partner Memos. Consultants Say It's Like Having '100,000 Senior Partners on Tap.' Lilli Handles 500,000 Queries/Month. The Firm Won't Say How Many Analyst Hours It's Replaced.

August 2023: McKinsey launched Lilli — an internal generative AI platform trained on 100,000+ proprietary documents spanning 70 years of consulting memos, client decks, and research. By mid-2024 it was handling 500,000 queries/month across 70% of McKinsey's 45,000 employees. Partners describe it as 'a junior consultant who has read literally everything we've ever written.' The firm refuses to publicly disclose headcount impact, but analyst-track hiring slowed and internal slides leaked to Business Insider showed 'average time to deck draft' falling from 4 hours to 45 minutes. Industry-wide, the Big 3 consulting firms are now racing to replicate the model.