The cautionary tale of the hedge fund quant and the $30m he does not have
As we reported yesterday, there is some beef between Cubist, the quant trading arm of hedge fund Point72, and Xin Jin, a former research lead there. Cubist says Jin used AI tools to steal its source code for eventual use at a rival. Jin says he did not.
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Yesterday, Jin filed his own affidavit and 'memo in opposition' to Cubist's claims. There, Jin categorically denies that he ever "misused Cubist's Confidential Information, used AI tools to take or misuse it, or "exfiltrated" any of the AI output."
Jin says his use of Cubist's AI tools was for his work at Cubist. The accompanying memo says his job at the fund ‘included monitoring and improving model performance, combining existing models, and generating new ideas for research and conducting that research, all of which required him to understand every model the team used or was developing.’ In his affidavit, Jin says reading, reviewing and improving the team’s code and research "was my job.”
Jin also claims that many of the 4,117 individual queries that Cubist says he used to extract information via Claude Code and Codex were written by AI agents and that to the extent that he "repeatedly" deleted prompt history and output folders, this was simply him deleting AI hallucinations or responses that weren't useful, rather than him attempting to conceal anything.
Cubist's own complaint accused Jin of "data mining and synthesizing other people’s work at Cubist in order to refine it and use it at a rival.”
Most notably, Jin wants the $30m that he says Cubist owes him for compensation and investments made during the time that he worked there. He says that more than $20m of this is in the form of shares that he was "required to purchase" with his bonuses. Jin claims that Cubist seems to be treating this money as forfeited because it fired him for cause. He was fired two days after disclosing that he had accepted another job.
A spokesperson for Cubist said: "The claims in this filing are without merit. We brought this action to protect confidential information, and we will respond in the appropriate legal forum."
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