Probook
Chief Architect
A voice agent is not reliable because it answers well. It is reliable when the caller’s job gets done, or the failure is caught, bounded, and recoverable.
What I’m building →Christian Yongwhan Lim New York
I turn hard technical problems into systems and teams that can keep solving them.
Chief Architect at Probook. Director of Internships at the ICPC Foundation. Adjunct at Columbia University.
Across engineering, teaching, and mentorship, I care about the same finish: a system that keeps its promises under pressure and a person who can carry the work forward without me in the room.
01 / Current work
Three roles. One way of working.
ICPC Foundation
Director of Internships
Pair talented students with consequential work, honest feedback, and mentors who steadily hand over the decisions that matter.
136 completed internships →Columbia University
Adjunct
Teach the moment before the algorithm: how to model an unfamiliar problem, expose uncertainty, and choose the next useful test.
Courses and teaching →02 / How I think
Three questions
I keep asking.
- 01
What must be true at the finish?
If we cannot observe the result, we do not yet have a useful goal.
- 02
Which belief could break the plan?
Test that one first. Architecture should follow evidence, not fashion.
- 03
Who can carry it next?
If the work stops when its original builder leaves, it is not finished.
03 / Evidence
The record matters more than the claim.
80/80
136
2×
Made a noisy evaluation useful for decisions
Scores shifted across models and longer conversations, so I tested when pooled evidence could be trusted. Calibration raised the readout from 0.712 to at least 0.95, exposed an evidence knee between 160 and 320 words, and passed all 80 reproducibility checks.
ICPC internships completed
A global program designed around real work, accountable mentorship, and student ownership.
World Finals teams coached
Competitive programming as a discipline for judgment, teamwork, and learning from failure.
“He has had a bigger impact in that short time than almost anyone has had in the history of North America.”
04 / Field notes
The lessons I had to earn.
05 / Contact