About
I started a company, served as CTO, grew a team to 35, and eventually walked out of that team. I’ve failed more than I’ve succeeded. These days I’m back to writing code, and I write about those failures here.
What I believe
- Discovery over delivery, outcome over input. Process matters, but process gets judged by whether it ends in a win.
- Cynicism is the worst stance. You see what you know, and you see what you’re trying to learn.
- Don’t judge. Be curious.
- There’s no universal law that runs through life. Everyone has their own path.
What I’m doing now
I stepped down as CTO and went back to writing code. With my partner Ellie, I’m building a small product and experimenting with AI agent workflows. I also work as a Fractional CTO for companies that are not ready to hire a full-time CTO but cannot keep postponing important technical decisions. I publish 1–2 posts a week, sometimes about organizations, sometimes about code, sometimes just about my own failures.
Fractional CTO
I review actual code, operating evidence, and product journeys, then turn business concerns into priorities and verification criteria an internal team can execute. The scope includes product and API architecture, AI production readiness, release safety, web and mobile state boundaries, and AI-native ways of working.
I do not take over feature tickets or act as a development outsourcing vendor. The goal is to leave the team with a better decision system, not a permanent dependency on an outside consultant.
The detailed service page is currently available in Korean: Fractional CTO. For a first conversation, think of it as a coffee chat and send me an email.
These posts represent me best
- Four Years at IHFB: A Retrospective — Growing a team from 3 to 35 and eventually leaving. This is the starting point.
- How a 15-Year CTO Vibe-Codes — Why I stepped down as CTO and went back to writing code.
- No Future for the Org That Doesn’t Win — The starting point of my view on organizations.
- Installing Claude Code Across Your Org Doesn’t Make It AX — A paradox about org transformation in the AI era.
- Reading The Score Takes Care of Itself: On Leadership — A record of my own failures, surfaced by Bill Walsh’s book.
Background
I’ve cycled through 0→1 product building and team building. I haven’t bounced through many teams, but I’ve passed through a few important cycles deeply.
- Loopetto — Co-Founder & Indie Hacker (2025–present). Product experiments for small teams.
- Fractional CTO — (2026–present). Product architecture, AI production readiness, release safety, web and mobile systems, and AI-native operating models.
- IHFB — CTO / R&D leadership (2021–2025). Built the org from 3 to 35.
- Todait Inc. — Founder & CEO (2015–2021). A study planner. Wound down the company.
Technically I work across Go, PostgreSQL, React, SwiftUI, and AI agent workflows. I care more about a product’s source of truth, real user journeys, and verifiable completion criteria than the names of the technologies involved.
I love content too. I once wanted to be a storyteller, and I still get easily moved by good narrative. I follow F1 race by race, and I’m writing an IT fiction series (Korean only) set in Pangyo (the Korean equivalent of Silicon Valley).
Contact
I post first on Threads when a new piece goes up. Especially happy to talk product, writing, organizations, or AI workflow.
Focus areas
- AI coding
- AI agents
- startup product development
- retrospectives
- team building
- leadership
- Go
- iOS
Recent posts
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March–April 2026 Retro: A Bad Partner, a Bad Mentor
One year after leaving the company, two months spent in front of writing, product, and people. An honest retrospective on failing to be a good partner or a good mentor.
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Books I Read in Q1 2026
Notes on the 10 books I read in Q1 2026: Stoner, The Obstacle Is the Way, Meditations, Source Code: My Beginnings, Bird That Drinks Blood, the second Krafton Way book, Lost and Founder, The Score Takes Care of Itself, Formula One, and Principles.
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Reading 'The Score Takes Care of Itself': On Leadership
Notes on Bill Walsh's leadership book 'The Score Takes Care of Itself.' The good-talent-bad-attitude equation, his declaration that teaching is the very definition of leadership, and the upward leadership chapter. The three-time Super Bowl winning coach's principles, read against my own failures.
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The Moment You Spin Up an AX Team, You've Already Lost
The paradox of setting up an AX task force. MIT NANDA found the successful 5% weren't led by central AI labs but by line managers on the ground. What I learned from going from consultant to CTO. The first principle of organizational AX isn't tools — it's people and the organization.
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When Package Install Becomes a Hack: Why Zero Dependency Matters
In March 2026, the litellm and axios supply-chain attacks hit back-to-back. I trace ten years of dependencies turning from convenience to trust to risk, and use code to show why zero-dependency design is survival, not minimalism.
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AI Native Engineer: Taste Built on Principles
Being good with AI tools doesn't make you an AI Native Engineer. Taste without principles is guesswork; principles without taste stay academic. After hitting the wall in iOS, getting blindsided as a Maker, and falling into the sorcerer's apprentice trap, I came to one conclusion: an AI-era engineer's identity isn't the toolkit, it's taste built on principles.