Founding Engineer (Full Stack)

About the role

About the Role This is a founding engineering role at a fast-growing, seed-stage startup building AI-powered autonomous product demo agents for B2B GTM teams. The company has tripled in the past month, is backed by top-tier investors (Series A/B range), and is now assembling a small A-team to scale. You will be one of two founding engineers, working directly with the CTO — setting the technical culture and architecture for everyone who comes after. The technical surface area is broad and genuinely novel: voice, browser agents, LLM orchestration, generative UI, reinforcement learning, and self-improvement loops. There is no narrow lane here. The best problems are unsolved because nobody has had to solve them before. No visa sponsorship available. On-site in San Francisco, 5 days/week required. What You'll Do You'll own work across four core technical pillars: The Agent: LLM orchestration, conversation flow, tool use, and voice. Building agents that understand products they've never seen and explain them clearly to prospects with varying levels of context. The Experience: Embeddable, generative UI that adapts in real-time — fast loads, complex interactive demos, responsive across products and screen sizes. The Platform: Customer-facing tooling for configuring agents, managing conversation flows, reviewing transcripts, and measuring performance. Evals & Self-Improvement: The pipeline that measures agent quality, detects regressions, and feeds learnings back so demos improve without manual intervention. Infrastructure: Zero-cold-start reliability — when a prospect clicks "start demo," the agent responds instantly. In practice, your week might look like: Diagnosing a conversation log to find where an LLM lost the thread during a pricing objection, then shipping a fix to the orchestration layer by lunch. Prototyping a generative UI widget that adapts its layout in real-time based on prospect intent — demo-able by end of day. Tracing an eval regression to a prompt change, rolling it back, and adding a test to prevent recurrence. Designing agent versioning infrastructure from scratch so customers can preview changes before they go live. What We're Looking For Required: 5+ years of full-stack engineering experience, having built and shipped products at a VC-backed B2B SaaS startup with paying customers. Proficiency in React (frontend) and Python (backend). Hands-on experience building and shipping production AI agent features: LLM agents, RAG pipelines, or agent orchestration frameworks (e.g., LangChain, LlamaIndex). Ability to design, implement, and maintain an evaluation pipeline for model outputs, including regression tracing and rollback mechanisms. Experience building versioning and preview mechanisms for deployed AI agents. Strong front-end skills and UX sensibility; demonstrated ability to build polished, customer-facing products. Comfort translating user feedback and product requirements directly into implemented features. Strong engineering judgment — you know when something is ready to ship and when it isn't. Bachelor's degree in Computer Science or a related technical field. Ability to work on-site in San Francisco 5 days per week. Nice to Have: Experience at a VC-backed sales technology or GTM tooling startup. Familiarity with the interactive demo / product experience tooling space (e.g., companies like Walnut, Demostack, Navattic, Arcade, Storylane, or similar). Compensation & Benefits Salary: $180,000 – $230,000 USD annually Founding engineer equity commensurate with role and stage Full-time position Location San Francisco, California, United States On-site, 5 days per week No visa sponsorship available