Junior Software Engineer

About the roleMost job posts are designed to collect as many applications as possible.This is not one of them.At Simplify, we work directly with startup founders to help them hire for high-priority roles.We're partnering with a top AI training lab in San Francisco to hire a junior software engineer — and they pay like it's a senior role: $300K base + equity + bonus, for new grads.About the companyOne-liner: Building high-fidelity RL environments used to train frontier AI models on real software-engineering workStage: 11–50 people, HQ in SF. They work directly with the top AI labs — their environments are used to train state-of-the-art models.Today, AI models learn coding from static datasets and toy problems. This team builds the realistic, simulated engineering environments — long-horizon tasks, real tooling, real failure modes — that frontier labs use to train and evaluate the next generation of coding agents.What you'll work onDesign and build reinforcement-learning tasks and environments for software-engineering challengesOwn the full lifecycle: from task concept through evaluation against frontier modelsEvaluate coding-agent outputs and identify subtle failure patternsBuild Python-based systems, harnesses, and tooling around model training and evalsWork with Docker/Linux environments that mirror real engineering workOwn problems end-to-end in a small, fast-moving teamMust-haveStrong Python skillsExperience working with the latest AI tools and modelsExceptional problem-solving ability — strong technical fundamentals and intuition for AI model behaviorAble to work independentlyIn person in San FranciscoUS work authorizationNice to haveML or AI experience (e.g., you've trained your own models) — not requiredStrong math/CS background (competitions like USACO/ICPC/olympiads)Competed in quiz bowl, debate, roboticsImpressive personal projectsWhy join$300K base + equity + bonus — at the junior levelYour work directly shapes how frontier AI models learn to do real engineeringSmall fast moving team, no bureaucracy — high ownership from day oneWork at the frontier of RL, agents, and evaluation with the top AI labs as your customers