Senior Full Stack Engineer

This is a job that Jill, our AI Recruiter, is recruiting for on behalf of one of our customers. She will pick the best candidates from Jack's network. The next step is to speak to Jack. Job Title Senior Full-Stack Engineer Salary $180k-$200k + Equity Company Description blok is an AI-native startup backed by MaC VC, Protagonist, Weekend Fund, and a16z scouts, building behavioral simulation systems. Founded by exited founders and researchers from Stanford and MIT, they help product teams predict human behavior at scale by testing decisions through AI agents before shipping. Job Description As a Senior Full-Stack Engineer at blok, you will build production systems that turn complex agentic simulations into actionable product insights. Working across Python and React/TypeScript, you’ll own features end-to-end within a high-velocity engineering tribe, bridging the gap between raw behavioral data and critical product decisions for high-growth customers. Location San Francisco, USA Why this role is remarkable Join an elite team of 15, including exited founders and researchers from Stanford, MIT, Discord, and Airbnb, solving frontier AI problems.Work at the cutting edge of behavioral science and AI, building simulation systems that actually predict how real users think and act.Experience high-velocity ownership with bi-weekly shipping cycles, backed by top-tier investors like MaC VC, Weekend Fund, and a16z scouts. What You Will Do Build and evolve the core Python platform used by customers to design experiments, run simulations, and explore behavioral outputs.Translate raw agent behavior into intuitive product functionality, bridging the gap between complex backend simulations and frontend user experiences.Design and implement systems that provide visibility and trust, helping users understand why the AI simulated specific human behaviors. The ideal candidate Over 6 years of experience building end-to-end production systems using Python and React/TypeScript in high-stakes environments.Proven track record with AI-native applications, specifically agentic systems or LLM-powered products that solve real-world user problems.A product-minded engineer who thrives in ambiguity, values radical candor, and takes extreme ownership of outcomes rather than just code. Who are Jack & Jill? Ok, I'll go first. I'm Jack, an AI that gets to know you on a quick call, learning what you're great at and what you want from your career. Then I help you land your dream job by finding unmissable opportunities as they come up, supporting you with applications, interview prep, and moral support. And I'm Jill, an AI Recruiter who talks to companies to understand who they're looking to hire. Then I recruit from Jack's network, making an introduction when I spot an excellent candidate. How does this work? Jack's an AI agent for job searching and career coaching. He works for you.Jill is the AI recruiter working for the company. She recruits from Jack's network.If it's a match and the company wants to meet you, they'll make the intro. In the meantime, if you'd like, Jack will send you excellent alternatives. We never post fake jobs This isn't a trick. This is an open role that Jill is currently recruiting for from Jack's network. Sometimes Jill's clients ask her to anonymize their jobs when she advertises them, which means she can't share all the details in the job description. We appreciate this can make them look a bit suspect, but there isn't much we can do about it. Give Jack a spin! You could land this role. If not, most people find him incredibly helpful with their job search, and we're giving his services away for free.