A technical leadership playbook
Concrete mechanisms for decision clarity, early risk communication, apprenticeship, sponsorship, recognition, and organizational memory.
Use the playbook →
Production AI · Architecture · Reliability
Reliable AI systems, built for the real world.
I’m Christian Yongwhan Lim. I help teams turn ambitious AI products into dependable systems through architecture, evaluation, observability, and recovery.
I turn ambiguous, high-stakes technical work into measurable decisions, reliable systems, and organizations that can operate without depending on one person.
Chief Architect at Probook · Adjunct at Columbia · Director of Internships at the ICPC Foundation. Formerly Google Research and Two Sigma.
New York, 2026
Current proof · September 2026
Explore the work →
- Operations research Decision-making across quality, cost, risk, and time
- ITCS 2027 Cascade-centrality paper submitted
- ICPC University Learning commons rebuilt for students, coaches, and organizers
How I can help
Start with the problem in front of you
Across AI products, programming contests, and global learning programs, I do the same kind of work: define success, expose failure modes, and build systems that remain dependable under pressure.
01 · Primary
Make a production AI system dependable
Architecture, evaluation, observability, workflow state, latency, and recovery across the full system—not only the model.
Discuss the system → 02 · LearningBuild a technical-learning environment
Curriculum, deliberate practice, coaching, feedback loops, mentorship, and durable community leadership.
Compare approaches → 03 · CollaborationBring the work into a room
Speaking and substantive collaboration on AI reliability, engineering leadership, problem solving, and technical education.
Explore a fit →“He has had a bigger impact in that short time than almost anyone has had in the history of North America.”
Selected work
View all selected work →
A few things that define the body of work
01 / Case study
02 / Research
03 / Reliability
Building a technical-talent pipeline that can outlast its builders
A public case study in connecting selection, contribution, mentorship, measurement, shared ownership, and succession.
136 completed internships · 14 active interns · 9.6/10 average experience across 86 responses Read the case study →Cascade centrality
Hardness, approximation, structural laws, and network augmentation supported by exact computation.
ITCS 2027 submitted · two focused manuscripts in preparationSee the research program →Contest engineering
Adversarial validation and release discipline for high-stakes programming contests.
Specification · independent solutions · failure catalogue · data · CI · judge reviewUse the release field guide →Working Notes
Increment All Divisors
An annotated AtCoder solution using reverse traversal on the divisibility order, affine operation counts, and a feasible interval.
Open the notebook →What fifteen years in the ICPC changed about how I solve problems
Reflections across competing, coaching, judging, organizing, and teaching—and what those roles reveal about the real work of problem solving.
Read the note →How I review an ICPC contest with a team
The scoreboard records outcomes. A useful review reconstructs the decisions, failure modes, and team interactions that produced them.
Read the note →