Founding Engineer

About the Role Join a small, high-velocity founding team building multi-modal AI agents across voice, SMS, and email for a vertical B2B SaaS platform that reached seven figures ARR within months of launch. As a Founding Engineer, you'll own one of four core domains end-to-end — B2B product, agent quality, family graph infrastructure, or B2C consumer product — and make product decisions directly alongside customers with no PM layer between you and the work. What You'll Do Own an entire product domain from architecture through daily production shipping. Join customer calls, synthesize feedback, and drive product decisions independently. Build and optimize multi-modal agents targeting sub-500ms voice latency, high SMS response rates, and persistent conversation state across channels. Establish architecture and quality practices for non-deterministic systems — evals, prompt versioning, guardrails, and drift detection. Work full-stack across React/Next.js frontends, Node.js backends, and Python voice services. What We're Looking For 3–8 years of full-stack engineering experience with a strong record of shipping 0-to-1 products at high-growth startups, as a founder, or within new vertical teams at large tech companies. Strong proficiency in TypeScript (Node.js, React/Next.js) and hands-on production experience with LLM APIs or agent SDKs (e.g. Anthropic, OpenAI, Vercel AI SDK, or similar). Depth in at least one domain: production voice/SMS agents, long-running agent state and memory, B2B2C or marketplace product architecture, or agent evals and guardrails. Demonstrated ability to make product decisions independently and conduct customer discovery without a dedicated PM. Python experience with real-time voice pipelines (STT/TTS, low-latency audio) or evaluation tooling is a strong plus. Experience with infrastructure tooling such as Redis, job queues, observability platforms, or deployment pipelines is a plus. Founder background with real traction (revenue, funding, or acquisition) and clear articulation of lessons learned is a plus. Strong CS fundamentals; a degree from a rigorous CS program is a plus for candidates earlier in their career. Must be authorized to work in the US — no visa sponsorship available. Compensation & Benefits Salary range: $180,000 – $250,000 USD annually, plus equity. No visa sponsorship is available. Location On-site, five days per week in Chelsea, New York City .