Sachith Gunasekara

Senior AI Engineer @ Gapstars · Instructor @ StemLink

prof_pic.jpg

Hi! I’m Sachith, a Senior AI Engineer at Gapstars, working with Envision AI Labs in Leiden, Netherlands. Most of my days revolve around one question: how do we know an AI system is actually good? I build retrieval benchmarks and evaluation frameworks for RAG and agentic systems, and I make sure every insight we generate from pharmaceutical and clinical data can be traced back to its source. Before this, I built multi-agent systems at Arcadea Group and Surge Global, after graduating at the top of my class (First Class, ranked 1st of 125) in Computer Science from the University of Kelaniya.

On the research side, I’m fascinated by how language models reason, and how we can help them reason better without simply throwing more compute at the problem. My latest work, iSelf-Discover, asks a deceptively simple question: should a model plan its reasoning in structured JSON or in plain language? Plain language won, by up to 18.9% on MATH. Before that, I helped build OpenBezoar, a recipe for training small, open instruction-following models on a modest budget.

I love sharing what I learn. I teach on StemLink’s AI Engineering Bootcamp, where I get to watch learners go from their first transformer to working multi-agent demos. I’ve also given talks such as A Step Beyond the Hype and Implementing AI Agents, and I write the occasional deep dive, like nanoJAXGPT, a hands-on introduction to JAX/Equinox. Looking ahead, I’m keen to pursue a PhD in Computer Science focused on making LLMs reason better and more efficiently. If that overlaps with what you’re working on, I’d love to chat!

news

Feb 01, 2026 Industry Joined Gapstars as a Senior AI Engineer, placed at Envision AI Labs (Leiden, Netherlands)
Sep 01, 2025 Teaching & Talks Started teaching as an Instructor on the StemLink AI Engineering Bootcamp
Aug 01, 2025 Awards & Honours Selected as a Youth Delegate for the Global Leadership Program at Brasenose College, University of Oxford
Jul 01, 2025 Research Released our pre-print Effects of structure on reasoning in instance-level Self-Discover on arXiv
Jun 01, 2025 Industry Joined Arcadea Group (Toronto, Canada) as a Senior AI Engineer
Apr 01, 2025 Teaching & Talks Gave an invited talk, A Step Beyond the Hype: A Journey Through Modern AI, at the IEEE Student Branch, Wayamba University of Sri Lanka
Apr 01, 2025 Industry Promoted to Machine Learning Engineer at Surge Global
Oct 23, 2024 Research Published nanoJAXGPT: A pedagogical introduction to JAX/Equinox on the Hugging Face blog (code)
Oct 01, 2024 Community Served as a Judge at Sri Lanka Artificial Intelligence Competition (SLAIC) 2024, IEEE Young Professionals Sri Lanka Section
Aug 01, 2024 Teaching & Talks Delivered an invited workshop, Implementing AI Agents, for university undergraduates at AI-Driven Sri Lanka
Apr 01, 2024 Research Released our pre-print OpenBezoar: small, cost-effective and open models trained on mixes of instruction data on arXiv
Mar 27, 2024 Awards & Honours Awarded Gold medal for best performance in Computer Science in the Faculty of Science, University of Kelaniya at the 142nd General Convocation
Dec 01, 2023 Community Served as a Mentor for an AI Bootcamp final competition at IEEE Young Professionals - Sri Lanka
Oct 13, 2023 Awards & Honours Recognized as the Best Presenter at the 4th International Conference on Applied and Pure Sciences (ICAPS 2023) - Kelaniya
Oct 01, 2023 Industry Promoted to Associate Machine Learning Engineer at Surge Global
Jul 01, 2023 Education Graduated at the top of the class from the University of Kelaniya with a Bachelor of Science Honours Degree in Computer Science (First Class Division)
Mar 13, 2023 Industry Joined Surge Global as a Data Science Intern
Feb 02, 2023 Awards & Honours Received Dean’s List award for Academic Year 2019/2020 at University of Kelaniya
Jan 29, 2023 Awards & Honours Received Dean’s List award for Academic Year 2020/2021 at University of Kelaniya
Nov 15, 2022 Awards & Honours Achieved Second Prize at the IEEE SA P2834 Student Challenge 2022, Valencia, Spain
Jul 19, 2021 Education Was selected for the specialized Computer Science Honours program at the University of Kelaniya based on exceptional academic performance
Feb 19, 2021 Awards & Honours Received Dean’s List award for Academic Year 2017/2018 at University of Kelaniya
Feb 14, 2019 Education Secured admission to the Bachelor of Science program at the University of Kelaniya, Sri Lanka

latest posts

selected publications

  1. Project Report
    OpenBezoar: Small, Cost-Effective and Open Models Trained on Mixes of Instruction Data
    Chandeepa Dissanayake, Lahiru Lowe, Sachith Gunasekara, and 1 more author
    arXiv preprint, Apr 2024
  2. Extended Abstract
    Capturing sentence-level positional data into N-gram profiles for document classification
    L M S Gunasekara, and H K S Premadasa
    ICAPS, Faculty of Science, University of Kelaniya, Sri Lanka, Apr 2023
  3. Preprint
    Effects of structure on reasoning in instance-level Self-Discover
    Sachith Gunasekara, and Yasiru Ratnayake
    arXiv preprint arXiv:2507.03347, Jul 2025