Probook
Chief Architect
I work on the path from a caller’s words to a completed job: speech, tools, business-system state, and repair when part of that path fails.
What I’m building →Christian Yongwhan Lim New York
I build reliable AI systems and teach people to solve difficult technical problems.
Chief Architect at Probook. Director of Internships at the ICPC Foundation. Adjunct at Columbia University.
At Probook, I work on voice agents where a timeout cannot quietly become a duplicate appointment or message. At Columbia and ICPC, I teach people to solve unfamiliar problems and explain why their solution works.
01 / Current work
What I work on
ICPC Foundation
Director of Internships
I connect students with technical projects and mentors. Interns make useful contributions and take increasing responsibility for their work.
136 completed internships →Columbia University
Adjunct
I teach competitive programming: model the problem, derive an algorithm, prove it correct, and implement it within the constraints.
Courses and teaching →02 / How I think
How I approach a problem
- 01
Define the result and the test.
If the result cannot be observed, the goal is not precise enough.
- 02
Find the assumption that could change the decision.
Test it early, before it becomes architecture.
- 03
Make the work understandable to the next person.
Document the decision, how failure appears, and what to do next.
03 / Evidence
Selected work and results
r=.91–.96
136
2×
Set a minimum length for writing samples
I tested whether a short sample could stand in for a full document when scoring six qualities of writing. Correlation stayed high at 250 tokens (r=.91–.96) and fell at 100 (r=.71–.76), so later comparisons use at least 250 tokens. All 80 reproducibility checks passed.
ICPC internships completed
Interns have shipped and maintained the problem archive, regional sites, journal, mobile apps, contest platforms, and training programs.
World Finals teams coached
Columbia reached the 2022 and 2024 World Finals and won silver at the 2024 North America Championship.
“He has had a bigger impact in that short time than almost anyone has had in the history of North America.”
04 / Field notes
Writing about the work
05 / Contact
What are you working on?
Tell me what you are trying to build, where it breaks, and what you have already tried.