Jeonghwan Kim — Writing https://jeonghwankim.dev/writing I build and ship software end-to-end — from system design to deployment. Full-stack web, native iOS/watchOS, and real-time systems, across AI, audio, mental health, legal tech, and neuroscience research. en When the Evidence Changes, Does the Model Really Update? https://jeonghwankim.dev/writing/when-evidence-changes https://jeonghwankim.dev/writing/when-evidence-changes Wed, 29 Jul 2026 00:00:00 GMT I repeated every perturbation condition three times. The leading diagnosis was highly reproducible; the ordering and scoring below it was not — which killed my original product hypothesis. Part 2 of The Differential. Getting the Diagnosis Right Is Not the Same as Reasoning Reliably https://jeonghwankim.dev/writing/getting-the-diagnosis-right https://jeonghwankim.dev/writing/getting-the-diagnosis-right Wed, 29 Jul 2026 00:00:00 GMT A frontier model ranked the correct diagnosis first on a masked neuromuscular case. Then I started removing evidence — and its confidence didn't move the way it should. Part 1 of The Differential. A self-audit of a production SaaS https://jeonghwankim.dev/writing/a-self-audit-of-a-production-saas https://jeonghwankim.dev/writing/a-self-audit-of-a-production-saas Sun, 19 Apr 2026 00:00:00 GMT I sat down for a day and attacked my own app. Six categories of finding — and what I'd build into the next project from day one.