Fundraising Fox

Christ Xu

Founder

Founder at Rational

United States

FoundedRational · YC

About

Christ Xu is a CTO at Rational who previously served as a Senior Software Engineer at Tencent and held roles as an ML Engineer at Jane Street and Software Engineer intern at OpenAI. He has a background in competitive mathematics and algorithm research.

Founder at RationalYC S26

Intro paths

YC

Christ went through Y Combinator (Summer 2026) — any YC alum in your network can reach them through the YC community.

GP

Their group partner at YC was Jared Friedman, YC Group Partner — the partner who ran Rational's batch and knows the company first-hand. YC profile ↗

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In turn, Christ can intro founders to Rational's investors below.

Rational's investors · 1

Y CombinatorSan Francisco · $500K checks · since 2026

Co-founders at Rational

JMJibril Moinuddin
Jibril MoinuddinFounder

Experience

  1. RationalCo-Foundercurrent2026 — present
  2. OpenAISoftware Engineering Interncurrent2026 — presentSan Francisco Bay Area
  3. TencentSoftware Engineer2026
  4. TencentSoftware Engineer2026
  5. Jane StreetIN:FOCUS 20262026New York, United States
  6. University of MichiganResearch Assistant2025

Skills & more

MATLAB1Python (Programming Language)1C#1PHPMySQL1JS1Adobe Acrobat1IT-Betrieb1Amazon Web Services (AWS)2DaVinci Resolve1Adobe Photoshop1Microsoft Office1

Languages Chinese · English · German

  • Introduction to Bio-Inspired Robotics — University of Cambridge

From Christ's professional profile.

Frequently asked questions

Who is Christ Xu?
Christ Xu is a CTO at Rational who previously served as a Senior Software Engineer at Tencent and held roles as an ML Engineer at Jane Street and Software Engineer intern at OpenAI. He has a background in competitive mathematics and algorithm research.
Where does Christ Xu work?
Christ Xu is Founder of Rational.
What companies did Christ Xu found?
Christ Xu founded Rational.
Where did Christ Xu go to school?
Christ Xu studied at Y Combinator; University of Michigan (Bachelor of Science - BS, Honors Mathematics); University of Michigan (Masters of Science, Applied Statistics).

Founder mafias

Y Combinator mafia8,773

Also came through, then founded or led a company.

Sam AltmanPresidentFounded Tools for Humanity +3Jessica LivingstonCo-founderFounded Y CombinatorAlexis OhanianYC Summer 2005Founded RedditFred EhrsamYC Summer 2012Founded Nudge +1Matt HuangYC Winter 2011Founded HotspotsTrae StephensYC Winter 2022Founded Pursuit +1

+ 8,766 more

Y Combinator mafia4,716

Also came through, then founded or led a company.

Ryan SheaEntrepreneurshipFounded StacksTarek MansourFounded KalshiSuhail DoshiEating beans & riceFounded Playground +1Subomi OluwalanaW22Founded ConvoyDarius "Bubs" MonsefS19Founded Sightbox +3Matthew ScholzFounded Oisin Biotechnologies +3

+ 4,709 more

University of Michigan mafia136

Also came through, then founded or led a company.

Erik TorenbergBachelor of Arts (B.A.)Founded VillageglobalDavid R. WaltBachelor of Science - BSFounded Sherlock Biosciences +5Chris VoigtBSEFounded Asimov +2Val AgostinoB.S.E.Founded Monarch +2Dillon ErbMaster of Architecture (M.Arch.)Founded Paperspace +2Eric LefkofskyFounded InnerWorkings +1

+ 129 more

OpenAI mafia68

Also came through, then founded or led a company.

Reid HoffmanBoard MemberFounded LinkedIn +2Sam AltmanCo-founder & CEOFounded Tools for Humanity +2Elon MuskCo-founder & former Co-chair / board memberFounded PayPal +5Ilya SutskeverCo-founder & Chief ScientistFounded Safe SuperintelligenceAravind SrinivasResearch ScientistFounded PerplexityDario AmodeiVP of ResearchFounded Anthropic

+ 61 more

Humboldt-Universität zu Berlin mafia5

Also came through, then founded or led a company.

Daniel HöpfnerBusiness Administration / EconomicsFounded pressmatrixFritz SeidelBetriebswirtschaftFounded Boomerang IdeasMarcus FosterSociology and AnthropologyFounded KlarismoHannes MühleisenMaster of Science - MSFounded DuckDB

Same school

Also attended Y Combinator2,000

Tarek MansourCo-founder & CEO of KalshiSuhail DoshiFounder of Mixpanel; founder of ParticleSubomi OluwalanaCo-founder & CEO of ConvoyMaroof AhmedFounder at Octopus VenturesJustin SwartPartner at Bitkraft Esports VenturesCollin WallaceGeneral Partner at Lobby Capital

+ 1,994 more

Also attended University of Michigan516

Erik TorenbergGeneral Partner at Andreessen Horowitz; founder of TurpentineKarim FarisInvestor at GV (Google Ventures)Glen AndersonPartner at Monta Vista CapitalAlexandra FarmerPrincipal at Intel Capital, North AmericaHannah KrootMarketing Lead at Intel CapitalScott ShawChief of Staff at Intel Capital

+ 510 more

Also attended Humboldt-Universität zu Berlin56

Theresa TongOperations Manager at FusionEvaLegal at NAPSusanna SzwajaWorkplace Managerin & Event Support at RedstoneJana GranigSenior Finance Manager at FoodLabsIsabelle ThierfelderSenior Investment Manager at Seed+SpeedNelly KarschAssociate at Seed+Speed

+ 50 more

Shared employers

Also worked at Rational2

Jim WalshAdvisor at Stage 1 VenturesJibril MoinuddinFounder at Rational

Also worked at OpenAI133

Reid HoffmanCo-founder of LinkedIn; Partner at GreylockPat GradyPartner at Sequoia CapitalGreg BrockmanCo-founder & President of OpenAIIlya SutskeverCo-founder of OpenAI; co-founder & CEO of Safe SuperintelligenceAravind SrinivasCo-founder & CEO of Perplexity AIDario AmodeiCo-founder & CEO of Anthropic

+ 127 more

Also worked at Tencent35

Leo LuInvestor at Foundation CapitalMichael CheungInvestment at Makers FundMuzzammil (MZ) ZaveriPartner at Audacious Ventures backing ambitious early-stage foundersKate WangAssociate at FinTech CollectiveLeonard TengAnalyst at DCM VenturesRandy LeeCo-founder and General Partner at Lifelike Capital

+ 29 more

Also worked at Jane Street55

Arvid LunnemarkFounder of Integrous Research; co-founder of CursorLeigh Marie BraswellPartner at KPCBIvory TangInvestor at ChemistryChang XuPartner at Basis Set VenturesAlexander GuInvestor at E14 FundChris ClarkInvestor at FalconX Credit / Pareto Vault

+ 49 more