Founding Product Engineer at River

As a Founding Product Engineer, you will build River’s core buyer-facing experience, including real-time voice calls and live browser-driven demos. You’ll work across the stack to develop agent logic, teach the AI new sales motions, and iterate rapidly based on real-time feedback from sales calls you helped ship earlier that week.

• Develop the buyer-facing product surface using Next.js and React, specifically focusing on the real-time live call and interactive demo experience.
• Architect and refine the agent logic using LLM APIs and browser automation tools like Playwright to teach the AI how to demo complex SaaS products.
• Collaborate directly with customers to learn their specific sales motions and integrate those insights into the product’s core discovery and closing capabilities.

• Has 2-4 years of experience with a strong TypeScript/React background and proficiency across the full stack including Node.js, Postgres, and Redis.
• Demonstrates deep interest or experience in real-time systems like WebRTC, browser automation, or building production-grade applications with LLM APIs.
• Possesses a strong product instinct and the drive to work in-person in NYC, preferring direct customer interaction over simply working through a ticket queue.

• Build a “Full AI Account Executive” that actually drives browsers and closes deals, moving beyond simple lead generation into high-stakes real-time automation.
• Join an elite team backed by the founders of Ramp and Kalshi, working alongside repeat founders who have already successfully exited their first company.
• Experience true founding-stage ownership where you onboard design partners yourself and see your code live on customer calls the same week it’s written.