Mid/Senior AI LLM Engineer (Full Remote - Spain)

Our Vision & Products 🚀 EverAI — Building the Future of AI Companionship One of the Top 15 Largest & Fastest-Growing AI Companies in the World 50 Million Users in 2 years — Help Us Reach 100M first, 500M next At EverAI , we’re shaping what it means to connect with AI. With 50 million users and counting , we're not just building products — we're creating entirely new categories. Our flagship product is the world’s largest AI companionship platform , redefining relationships for millions. It is governed by our proprietary moderation system, EverGuard — an internal AI designed to ensure everything we build is safe, ethical, and human-first . And we’re only just getting started! Our Team We are an enthusiastic, passionate and hardworking team of ≈ 100 people. Our founding team has strong entrepreneurial experience building and scaling web products from 0 to IPO. Alexis Soulopoulos [CEO] • 10+ years in Tech Executive Leadership • Co-Founder Mad Paws Holdings (from 0 to IPO) • Forbes 30 under 30 + Deloitte TechFast50 ’22 & ‘23 Michael Monin [Co-founder & CTO] • 10+ years as CTO / COO (web2/web3), 3 years in AI/LLM • Serial-entrepreneur: MTK Digital (exited / 0->$20m revenue) and Zipchat (AI Chatbot for E-commerce brands) Thomas Lacroix [Co-founder & CMO] • 8+ years in Customer Acquisition & E-commerce Growth • Serial-entrepreneur: Curatible (sold to Blackstone) and MTK Digital (exited / 0->$20m revenue) Maruša Fasano [CFO/Legal] • 25+ years in Finance, Strategy, M&A • Ex-CFO/M&A @Curatible (exited to Blackstone) • Ex-President of the Board @SotremoSA (exited) • Co-founder/CFO @SoftOne (exited) Your Role Most LLM roles stop at experimentation. Here, the models you improve power experiences for 50M+ users. Most of our traffic runs on self-hosted, fine-tuned open-weight models . On our internal roleplay evals, our smaller fine-tuned models can outperform much larger off-the-shelf models. Your job is to make them better. You’ll join a small AI team led by Marco, our LLM Tech Lead , working closely with our CTO, Product, Web and DevOps teams. You’ll work across data, post-training, evals, and model behavior, taking ideas from failure analysis to production. The problems are real: personalization, character consistency, long conversations, better evals, multilingual behavior, and faster training cycles. If you want to shape model behavior at consumer scale, this is the role. Key Responsibilities • Fine-tune open-weight LLMs using SFT, LoRA/QLoRA and post-training methods such as DPO and GRPO • Diagnose model failures and turn them into experiments. Decide whether the answer is better data, post-training, prompting or classifiers • Build training data and evals that directly shape what gets trained next • Improve model behavior across personalization, consistency, tone, multilingual and group interactions • Ship to production and use real user behavior to guide the next iteration • Speed up the training loop so experiments are faster, easier to compare, and more reproducible Your Qualifications • You’ve personally post-trained open-weight LLMs for a user-facing product and shipped them to production • You’ve worked where AI was core to the product or business , not an experimental side feature • Fine-tuning is core to your experience • Strong Python, PyTorch and Hugging Face , with hands-on GPU training and debugging • You build data and evals yourself and make decisions from evidence • You can take work beyond notebooks into production • You use AI tools daily in your own engineering work • You are fully comfortable working with uncensored models and explicit NSFW content , including harmful material when developing and evaluating moderation system Bonus points • Experience with conversational