AI Researcher (PHD) - Efficient & Interpretable LLMs

About

We’re building Graybox — a flexible platform for training, analyzing, and debugging neural networks in real time. Our next challenge: designing ultra-efficient large language models (LLMs) that are interpretable, adaptable, and under 256M parameters.

Job Description

We’re looking for a PhD student to help us extend WeightsLab to support LLM development, while also shipping a slim, high-quality LLM. You’ll contribute to both platform capabilities (e.g., transformer-level introspection, attention analysis) and model design.

This opportunity combines practical engineering with mechanistic interpretability: the goal is to understand the internals of small LLMs, intervene during training, and produce a model that’s not only efficient but also transparent and editable.

What You’ll Do

  • Extend Graybox to support transformer-based models and LLM-specific insights

  • Train and iteratively refine a sub-256M parameter LLM

  • Apply mechanistic interpretability tools and concepts to guide architecture choice

  • Enable interactive model operations: neuron pruning, attention head control, layer freezing

  • Benchmark performance vs. transparency trade-offs

  • Deliver a documented, reusable model with accompanying evaluation and tooling

Preferred Experience

You Might Be a Good Fit If You…

  • PhD student in NLP, Machine Learning, or a related area

  • Experience with LLMs (e.g. GPT-2, Mistral, Phi, etc.) and PyTorch

  • Familiarity with model introspection, transformer internals, and training workflows

  • Working knowledge of mechanistic interpretability methods

  • Strong experimentation skills and interest in tooling

Bonus (Not Required)

  • Experience with TransformerLens, Circuits, or interpretability frameworks (e.g. Captum)

  • Contributions to open-source LLM tooling or lightweight architectures

  • Interest in hybrid symbolic–neural approaches or efficient deployment

Additional Information

  • Contract Type: Internship (Between 3 and 6 months)
  • Location: Paris
  • Education Level: PhD and more
  • Possible full remote