(Senior) Machine Learning Developer (Junie)

Are you an engineer who loves diving deep into ML models, building standalone CLI tools, and exploring how far AI agents can go in autonomous coding? Do you want to rethink how software is built and use the tools you create every single day? About JetBrains We create intelligent software development tools for developers and teams. More than 15 million users, over 300,000 companies, and 88 of the Fortune Global Top 100 rely on our products to solve real, complex problems. Our mission is simple: make development teams more productive and AI adoptable at scale. What you’ll do We build Junie, our AI coding agent, available across JetBrains IDEs and as a standalone CLI. We're combining the latest advancements in AI and LLMs with our decades of software development expertise. We are working in three main areas: growing Junie CLI into a general-purpose agent independent of any IDE, optimizing model ensembling and setups for the best cost-to-intelligence ratio without compromising code quality, and pushing next-level autonomy so Junie can own, maintain, and evolve entire subsystems over multi-day horizons. You’ll have end-to-end ownership over these initiatives, taking work from early research to production code while shaping the future of autonomous development. Day to day, you will: • Develop and ship new features for Junie across CLI and model integrations. • Experiment with model setups, ensembling, and cost efficiency strategies. • Build and test autonomous agent behaviors for long-term project maintenance. • Own the full development cycle from initial research to production-ready code. • Use Junie daily to continuously iterate on its quality and user experience. What you’ll bring • Comfort taking full ownership of decisions and implementation. • The curiosity to challenge assumptions and experiment with new ideas. • The ability to learn new concepts quickly and adapt quickly. • A mindset focused on long-term impact rather than short-term workarounds. • Strong interest in autonomous AI systems and software engineering tools. What you’ll need • A proven track record of developing and shipping machine learning or full-stack software products. • Hands-on experience working with LLMs, prompt engineering, or agentic workflows. • The ability to write high-quality production code across the full development lifecycle. • Practical experience building or fine-tuning ML models. What success looks like In this role, success means taking bold experiments in agent autonomy and cost efficiency and turning them into reliable, production-ready capabilities. You'll know you're succeeding when Junie can tackle complex multi-day engineering tasks autonomously and the tool you build every day actively improves your own engineering workflow. Why join JetBrains? • Strong base salary. We offer competitive pay that reflects your skills and experience. • Flexible work location. Enjoy the freedom to work from home or from the office. • Remote work. Spend up to 30 days per year working remotely from abroad. • Extra time off. More days to relax, recharge, and do the things you love. • Medical insurance allowance. Enjoy peace of mind for you and your family • Learning and development opportunities. Access to conferences, courses, and language classes. • Relocation support. We help make your move as smooth and stress-free as possible. • Language classes. Pick up the local language or sharpen your English skills. • Fuel your day. Enjoy a hot meal or receive a lunch allowance on workdays. • Mental health support. To help you feel your best, we provide easy access to professional mental health services. • Sports benefit. Enjoy an on-site gym or sports club stipend. • Internal events. Join company-wide celebrations and team gathe