Founding Fullstack Engineer

San Francisco | Full-Time | $170k-$240k + 0.5%-1.0% Equity

Join Serif - Build Real AI Agents That Matter

Serif is redefining what AI agents can do in the real world. While most AI startups are busy building flashy demos, we're building functioning, revenue-generating agents that serve real customers. Our users-lawyers, agencies, brokers-trust us to automate critical workflows, not just answer questions.

We're already seeing $500K in revenue , backed by $5M in seed funding from General Catalyst , and trusted by 1,500+ paying customers . Serif is led by repeat founders (with 1 prior exit) and built by a product-obsessed team ready to reshape how individuals and small teams use AI. What We're Building

We're on a mission to create the first truly functional personal agent , capable of taking action , managing complexity, and integrating deeply into users' daily tools. This means designing systems that not only respond but perform-calendar scheduling, email triage, CRM updates, client workflows-so our users can stay focused and stress-free. About the Role

As Serif's Founding Fullstack Engineer , you'll own the technical backbone of the product and play a key role in shaping the next generation of intelligent agents. You'll work directly with the founders and collaborate closely with our small, high-trust team. You'll tackle hard technical challenges like: Building reliable AI agents that handle complex, multi-step tasks across multiple tools Designing integration frameworks for third-party systems (inboxes, CRMs, calendars, etc.) Architecting local-first systems with offline-sync and seamless state management Orchestrating distributed AI workflows with real-time responsiveness What We're Looking For • Experience & Education 3-5+ years as a fullstack engineer (ideally in a high-growth startup environment) Background in building and scaling backend systems Collaborative experience on a dev team; you've built real features with real teams B.S./M.S. in Computer Science or equivalent practical experience Technical Skills Deep experience with Node.js + TypeScript Expertise in systems design and backend architecture Comfort with fullstack development, including frontend frameworks and APIs Familiarity with AI tools (e.g., Claude , Cursor , vector DBs ) or experience integrating AI APIs Bonus: Interest in local-first technology and offline-sync models Soft Skills & Mindset You love to code, tinker, and ship You lead by example-reviewing code, setting standards, and mentoring others You're comfortable in high-ownership, high-autonomy environments You're active in the dev world-blogging, sharing projects, or building in public The Offer Salary : $170K-$240K (flexible based on experience) Equity : 0.5%-1.0% ownership in a high-upside opportunity Location : In-person 6 days/week in San Francisco Visa Sponsorship : Available on a case-by-case basis Hiring Timeline : We're ready to hire now Why Serif? Immediate Impact - You'll shape mission-critical systems used by real customers today True Ownership - Join at 0→1 and help define our technical foundation No Red Tape - We're building fast, smart, and focused Deep Product Love - We care deeply about UI/UX, not just backend logic Power Users - Our customers rely on Serif for real business tasks, not novelty ✉ Ready to build something that actually works?

Apply now at www.serif.ai or reach out directly to our founder, Zihua Liu.

Let's build the future of AI agents- for people who really need them.