Founding Software Engineer - Backend

ABOUT HYPERCUBIC At Hypercubic, we’re building AI systems that can understand, reason about, and rearchitect large-scale legacy applications running on mainframes and COBOL. We work at the intersection of program analysis, knowledge extraction, and agentic systems, applied to some of the most critical enterprise software in the world (banks, insurance, airlines, government, and more). We’re a small, deeply technical team in San Francisco, backed by top investors, and working with some of the largest organizations in the world. Learn https://www.hypercubic.ai/insights/mainframe-modernization-is-a-hard-and-fun-problem-to-solve why we're excited about mainframe modernization. ABOUT THE ROLE We’re looking for a backend engineer with unusually strong engineering and design taste. You will work directly with the CTO to design, prototype, and productionize AI-powered systems from first principles. This is a founding role with meaningful ownership over architecture, product direction, and engineering culture. It is suited for someone with strong fundamentals and comfortable operating across abstraction layers, from low-level system reasoning to high-level interactions. WHAT YOU’LL DO - Rapidly prototype new concepts and features to validate ideas before full implementation. - Ship AI-driven features end to end, from model interaction to user-facing workflows. - Set early engineering standards around testing, reliability, and code quality. - Translate ambiguous problem statements into concrete experiments, constraints, and working systems. - Lead architecture decisions and long-term technical direction with the CTO. - Collaborate with a highly diverse group of subject matter experts and customers from various industries (banks, insurance, airlines, and more). YOU ARE A FIT IF… - You care deeply about your work and the product. - You are comfortable with uncertainty and enjoy figuring out what to build before how to build it. - You have built complex agentic products or infrastructure. - You think in systems and feedback loops, not just features. - You can move fast and slow. Prototyping ideas in hours, then building enterprise-grade features to a high-quality bar. - You want to become world-class at AI engineering. - You have a bias for action and a track record of working in fast-paced environments with urgency. NICE TO HAVE - Strong testing intuition, including TDD and property-based testing. - Experience building and maintaining production-grade agentic or autonomous systems. - Exposure to legacy systems (especially mainframes or COBOL), compilers, program analysis techniques, or high-performance computing (HPC). - Familiarity with enterprise software constraints. LOGISTICS - Location: This role is in-person based in San Francisco, California. - Benefits: Hypercubic offers generous health, dental, and vision benefits, PTO, and relocation support as needed. - Sponsorship: Unfortunately, we are unable to sponsor new H1B employment visas at this time. However, we can support H1B transfers and OPT. LOGISTICS - Location: This role is in-person 5 days a week based in San Francisco, California near FiDi. - Sponsorship: Unfortunately, we are unable to sponsor new H1B employment visas at this time.   BENEFITS We offer the following benefits for our full-time employees: - Founding-team level equity, - Medical, Dental, and Vision benefits for you and your family - Life Insurance benefits - Retirement Plan (e.g., 401K) - Monthly stipend to support your wellness and commute - Daily lunches/dinners and snacks in the office to fuel you - Generous PTO and sick day policy to rest and recharge