Costin-Andrei Oncescu

ML researcher and Harvard CS PhD student with a competitive-programming background (IOI 2016/2017/2018 medalist for Romania, ICPC World Finals medalist). Research focuses on efficient LLM inference/training, including first-authored ICML 2026 work on mixture-of-experts decoding. Has held internships at quantitative trading firms Five Rings, Hudson River Trading and Jane Street, and at AI companies Together AI and Cursor.

Notes5

• Quant employment verification: CONFIRMED. The subject's own X bio states 'Interned @ Cursor, Together AI, 5 Rings, HRT, Jane Street', and the LinkedIn/enrichment work history independently lists Software Engineer Intern at Jane Street, Software Engineer Intern at Hudson River Trading and Quantitative Research Intern at Five Rings. Identity is supported by the IOI profile (Romania, IOI 2016/17/18), the Harvard SEAS directory (PhD student, [contact omitted]) and OpenReview. Employer classification: Jane Street, Hudson River Trading and Five Rings are quantitative proprietary trading firms / market makers; Cursor (Anysphere, AI coding) and Together AI (AI cloud) are NOT quant-finance firms and do not count toward the quant criterion. Actual quant internships are evidenced; the specific start/end months come only from the caller-provided index lead and are NOT independently confirmed. The index/enrichment layer is not treated here as independent primary-source confirmation.
• Quant employment verification: CONFIRMED. The subject's own X bio states 'Interned @ Cursor, Together AI, 5 Rings, HRT, Jane Street', and the LinkedIn/enrichment work history independently lists Software Engineer Intern at Jane Street, Software Engineer Intern at Hudson River Trading and Quantitative Research Intern at Five Rings. Identity is supported by the IOI profile (Romania, IOI 2016/17/18), the Harvard SEAS directory (PhD student, [contact omitted]) and OpenReview. Employer classification: Jane Street, Hudson River Trading and Five Rings are quantitative proprietary trading firms / market makers; Cursor (Anysphere, AI coding) and Together AI (AI cloud) are NOT quant-finance firms and do not count toward the quant criterion. Actual quant internships are evidenced; the specific start/end months come only from the caller-provided index lead and are NOT independently confirmed. The index/enrichment layer is not treated here as independent primary-source confirmation.
• Public Harvard email on the SEAS directory: [contact omitted].
• X account @costinoncescu self-describes 'PhD student in ML foundations @ Harvard. CS @ Oxford. IOI/ICPC WF medalist. Interned @ Cursor, Together AI, 5 Rings, HRT, Jane Street' - the self-authored statement tying the Olympiad identity to the quant internships.
• IOI record (Romania): Silver medal at IOI 2016 (33rd absolute, score 402), Bronze at IOI 2017 (89th), Bronze at IOI 2018 (95th).
• Career-stage dates (OpenReview): Oxford undergraduate 2018-2021, Oxford MS 2021-2022, Harvard PhD 2022-2027 - placing the three quant internships (2020, 2021, 2024) during undergraduate and PhD study.
• ML research: first author of 'Opportunistic Expert Activation' (ICML 2026) and co-author on 'Seesaw' and 'The Recurrent Transformer'; Google Scholar h-index 4, 72 citations.
• Competitive-programming handle 'geniucos'; co-winner of CEOI 2018 (Central European Olympiad in Informatics) alongside Mariusz Trela.
• ICPC World Finals: participated 2019 (16th) and won a Bronze medal in 2021 (11th).