ML Scientist - build the world's first conversational private bank

Our client is the world’s first conversational private bank.
They are building the smartest interface between customers and their money, providing the "unfair financial advantage" usually reserved for the ultra-wealthy.

Founded in January 2026 and backed by top European VCs, they are assembling a world-class team to deliver an AI-native banking experience built on transparency, simplicity, and trust.

Youmanista is recruiting a mid-exp (around 2/5 ans) Machine Learning Scientist and Senior (+5 years) for this early-stage company.

🧠 Your Mission
You will join a fast-moving team to build the AI brain behind the app. Everything you build will directly shape how customers interact with their finances.

🛠 Key Responsibilities

• ML development → Implement, train, and evaluate machine learning models across Hector's AI stack: both LLM-powered systems (agents, RAG, memory, etc.) and classical ML tasks (transaction classification, fraud detection, sentiment analysis, etc.).
• Evaluation & benchmarking → Build and maintain evaluation pipelines: dataset curation, metric computation, regression testing, and reporting across all ML systems.
• Experimentation → Run structured experiments to compare approaches (model architectures, chunking strategies, prompt variations, feature sets).
• Data quality → Work with the AI Engineering team to identify data gaps, quality issues, and improve the datasets that feed ML systems.
• Collaboration → Work under the guidance of Senior ML Scientists on R&D priorities and alongside the AI Engineering team on implementation and integration.

🎓 Skills & Knowledge
Must Have: ✅

• Proficient with AI coding tools, both assistive and agentic (Claude Code, Copilot, Cursor, or equivalent).
• Strong Python skills with experience using ML libraries.
• Solid foundations in machine learning: supervised and unsupervised learning, feature engineering, model selection, and evaluation metrics.
• Good understanding of NLP fundamentals: classification, embeddings, semantic similarity.
• Comfortable working with data: cleaning, exploration, labeling, and building reproducible pipelines.
• Ability to document experiments clearly and communicate results to the team.

Nice to Have: ✨

• Hands-on experience with LLM frameworks (ex: LangChain, LlamaIndex, Ragas, etc.) and prompt engineering.
• Familiarity with evaluation methodology for generative systems: faithfulness, groundedness, retrieval precision, and hallucination detection.
• Experience with RAG architectures: vector databases, graph databases, chunking strategies, hybrid search, reranking.
• Prior experience in a regulated industry (ex: finance, healthcare, legal, etc.).

👤 About You

For the job:

• 2+ years of professional experience in machine learning or data science.
• PhD or MSc in Machine Learning, NLP, Computer Science, or a related quantitative field is a big plus.
• Eager to learn and grow, you're looking for an environment where you'll be challenged daily and supported by experienced teammates.
• Rigorous and curious: you benchmark before you ship and read the paper before you adopt the framework.
• Thrive in early-stage environments where scope is broad, ambiguity is high, and ownership is real.
• Hungry for a real challenge: you're not looking for a comfortable seat, you want to build something that doesn't exist yet.
• Solid communication skills in English; French is a big plus but not required.

For the project:

• Frustrated by how traditional finance serves its customers, and motivated to break the mold to create something genuinely better for our users.
• Genuinely excited about making financial services accessible and trustworthy through AI.

📋 Interview Process
We aim to complete this within 2 weeks.
1. Discovery Call (30 min): Background, motivations…
2. Technical Deep-dive (1 hr): Production systems, data, and AI engineering.
3. On-site Pairing (2 hrs): Work with the team on a real-world problem.
4. Culture Fit: Coffee, lunch, or a drink to get to know the team.

🎁 Contract & Perks
• Contract: Full-time permanent (CDI).
• Salary: Starting from 65k+ euros (depending on experience) + BSPCE stock options.
• Remote: 3/5 days in our Paris office + 3 weeks per year full remote.
• Hardware: Best-in-class laptop + Unlimited Claude AI plan.
• Benefits: 100% covered health insurance & 100% Navigo pass coverage.