Founding Product Engineer

ABOUT Arceus is building the AI-native law firm for the next generation of category-defining companies. We help fast-moving companies move contracts through legal at record speed, with transparency, predictable pricing, and exceptional quality. We're hiring a Founding Product Engineer to build the platform that’s reinventing how legal work gets done.

You'll sit next to attorneys and AI engineers, turning real legal judgment into software that ships fast and holds a high bar. We have extremely high ambitions. You should too. This is an in-person role based in San Francisco. THE OPPORTUNITY We are seeing incredible demand for our product. The market is open for us to capture and emerge as the winners in this new category.

This is a rare chance to:

• Build the core product of a generational company from the ground up
• Work shoulder-to-shoulder with attorneys and AI engineers on a product nobody has built before
• Experience incredible career growth at a fast-growing company
• Set the engineering culture and standards for everyone who comes after you IDEAL CANDIDATE You're a product-focused builder who ships. You don't just close tickets — you have a point of view on what should get built and why, and you sweat the details of the user's experience. You've owned features end to end, made pragmatic calls under pressure, and you care about the craft without letting perfect block done.
• You think like an entrepreneur and operate like an owner
• You move fast and want your work in front of real users quickly
• You take complete ownership of outcomes and find a way to deliver
• You bring urgency and intensity to your work every day
• You take pride in going above and beyond what is expected
• You constantly look for ways to move faster, raise the quality bar, and become more consistent in how you execute
• You are resilient when things don't work and persistent enough to find another way WHAT SUCCESS LOOKS LIKE
• Day 7: You're onboarded, set up in the codebase, and shipping your first change
• Day 14: You are closing real tickets in production
• Day 30: You are owning features that customers feel
• Day 60: You own significant parts of the platform and have shaped how we build WHAT YOU’LL OWN We have an extraordinarily high bar and expect relentless, consistent execution. You are expected to show up every day with urgency, ownership, and a positive attitude, and to deliver results consistently.
• Build and own core product features across the stack, from data models to the interfaces attorneys and clients use every day.
• Partner closely with AI engineers and attorneys to turn legal workflows and review playbooks into reliable software.
• Make pragmatic architecture and tooling decisions that let us move fast now without painting us into a corner later.
• Own quality: write maintainable code, build for reliability, and take responsibility for what you ship in production.
• Help define engineering culture, standards, and hiring as the team grows.
• Move work over the finish line when it matters — customer experience always comes first. We ask a lot because we are building an exceptional company and engineering team. In return, you'll get a fast-track opportunity to grow your career, take on responsibility far beyond your experience level, and learn what it takes to build a disciplined, relentless, world-class engineering organization. EXPERIENCE - 1-3 years building and shipping production software, ideally at an early-stage company, or as a founder at your own company
• You are relentless, and will work 12+ hours per day, 6 days a week (yes, including weekends)
• You thrive in an environment with an exceptionally high bar, where everyone is expected to go above and beyond
• You have strong product instincts and full-stack ability (e.g., TypeScript/React on the front end, a modern backend stack, relational databases)
• You have built something with AI/LLMs, either in a job or on your own
• You have a track record of owning features end to end and making sound engineering trade-offs
• You are comfortable with ambiguity and worked in a fast-moving, high-ownership environment
• You have excellent judgment and communication, and a high bar for your own work COMPENSATION & BENEFITS
• Competitive base salary commensurate with experience: $140,000 – $180,000
• Competitive equity in the company
• Comprehensive health, dental, and vision coverage
• Catered lunches and dinners at the office
• Wellness and learning stipends
• Option to contribute to a 401(k)
• Unlimited PTO