Kaustubh Ponkshe

PhD Student, Machine Learning & Optimization Lab, EPFL.

headshot_new.jpg

INJ Building, Station 14

EPFL, 1015 Lausanne

Switzerland

I am a PhD student in Computer Science at EPFL, where I am part of the Machine Learning and Optimization Lab (MLO), advised by Prof. Martin Jaggi. I am supported by the EDIC Fellowship, and I contribute to Apertus — the largest (70B) fully open and compliant LLM training run to date.

I want to understand how language models learn. My research rethinks the training pipeline of foundation models — pretraining, midtraining, and post-training:

  • Knowledge-free & retrieval-grounded pretraining — training models that lean on external context instead of memorizing the world, to reduce parametric memorization and externalize memory.
  • Agentic pretraining — teaching models tool use and on-policy decision-making beyond passive next-token prediction.
  • Data & training dynamics — how midtraining and post-training data mixtures interact to shape reasoning and generalization.

Previously, I was a researcher at MBZUAI with Prof. Praneeth Vepakomma, where I worked on efficient and federated fine-tuning of large models, and on the safety and memorization behavior of LLMs. Before that, I completed my B.Tech in Electrical Engineering and M.Tech in Artificial Intelligence at IIT Bombay, where I also led the path-planning and controls teams of IIT Bombay Racing, building India’s first driverless racecar.

Outside research, I enjoy traveling (24 countries so far 🌍) and playing tennis 🎾.

news

Jan 22, 2026 Two papers — ABBA and Safety Subspaces are Not Distinct — accepted at ICLR 2026 :sparkles:
Sep 18, 2025 TokenSwap selected as a Spotlight at NeurIPS 2025 🎉
Sep 02, 2025 Apertus is out — the largest (70B) fully open and compliant LLM to date. Proud to have contributed! [paper] [models]
Sep 01, 2025 Started my PhD in Computer Science at EPFL, joining the Machine Learning and Optimization Lab with Prof. Martin Jaggi 🇨🇭
May 16, 2025 FedEx-LoRA accepted as an Oral at ACL 2025 (Main Conference) :sparkles:

selected publications

  1. Preprint
    Apertus: Democratizing Open and Compliant LLMs for Global Language Environments
    Apertus Team, and Kaustubh Ponkshe
    2025
    8B and 70B fully open-data, open-weights models, multilingual across 1000+ languages
  2. NeurIPS Publication Preview
    TokenSwap: A Lightweight Method to Disrupt Memorized Sequences in LLMs
    Parjanya Prashant*, Kaustubh Ponkshe*, and Babak Salimi
    2025
    NeurIPS 2025 (Spotlight)
  3. ACL Publication Preview
    FedEx-LoRA: Exact Aggregation for Federated and Efficient Fine-Tuning of Large Language Models
    Raghav Singhal*, Kaustubh Ponkshe*, and Praneeth Vepakomma
    2025
    ACL 2025 (Oral, Main Conference — top 2.1%)
  4. ICLR Publication Preview
    ABBA: Highly Expressive Hadamard Product Adaptation for Large Language Models
    Kaustubh Ponkshe*Raghav Singhal*, Rohit Vartak*, and 1 more author
    2025
    ICLR 2026; ES-FoMo @ ICML 2025 (Spotlight)
  5. ICLR Publication Preview
    Safety Subspaces are Not Distinct: A Fine-Tuning Case Study
    Kaustubh Ponkshe*, Shaan Shah*Raghav Singhal*, and 1 more author
    2025
    ICLR 2026; INTERPLAY @ CoLM 2025
  6. TMLR Publication Preview
    Fed-SB: A Silver Bullet for Extreme Communication Efficiency and Performance in (Private) Federated LoRA Fine-Tuning
    Raghav Singhal*, Kaustubh Ponkshe*, Rohit Vartak, and 2 more authors
    2025
    TMLR (J2C Certification — top 10% of accepted papers)