Hypercubic provides AI-native infrastructure for mainframe operations and modernization, helping enterprises understand, preserve and modernize legacy COBOL systems. Roughly 70% of Fortune 500 companies still rely on mainframes for core applications in banking, insurance, telecom, airlines and retail, while the COBOL workforce ages and retires. Its flagship product, Hopper, is an agentic development environment for IBM mainframes that combines a TN3270 terminal with AI to navigate z/OS workflows, write and edit COBOL, generate JCL, submit jobs and explain failures. Hypercubic was founded by former Apple machine learning engineers, is based in San Francisco, and is part of Y Combinator's Fall 2025 batch.