Notes
Notes
Short notes from the current moment.

Health · Data & Decision-MakingFeb 20, 2026
Andrej Karpathy posted his resting-heart-rate experiment on X.
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HealthFeb 9, 2026
Whenever my habits start slipping, I put on a CGM and switch back into good-habits mode.
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Video

AIFeb 7, 2026
Let AI take on more of the busywork, and live like this.
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AIFeb 5, 2026
How I use Claude Code, according to the new /insights feature.
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AIFeb 3, 2026
This feels like a kind of cold-start process required to work with AI.
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Engineering LeadershipJan 28, 2026
When I ended up becoming a CTO after coming back to Korea
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HealthJan 27, 2026
A study says measuring HRV before bed can predict insomnia.
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Health · AIJan 26, 2026
These days I record every part of my personal life and intentionally live with AI’s help.
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StartupJan 22, 2026
After starting a company with nothing but unreasonable confidence, the world around me changed.
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Data & Decision-MakingJan 22, 2026
1. What I look at first in a thesis defense, as a professor
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Startup · AIJan 22, 2026
[The Era of the One-Person Unicorn Has (Really) Arrived]
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StartupJan 22, 2026
First Profit, First Giveback (Finally)
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AIJan 18, 2026
Claude Code has been outputting ASCII tables a lot lately
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AIDec 25, 2025
AI can be superhuman in some domains and still lacking in others
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Data & Decision-MakingDec 20, 2025
One lesson I love most from working with smart people
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AIDec 16, 2025
Development, in the old sense of adding features and fixing bugs, is over
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AIDec 9, 2025
⚠️ Biases to watch out for when using LLMs as judges
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HealthDec 8, 2025
If you work hard because you want to do great work, your HRV drops
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Health · Data & Decision-MakingDec 2, 2025
Mirae Asset Chairman Park Hyeon-joo checks heart rate, glucose, and blood pressure for important decisions
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AINov 24, 2025
Cursor’s head of design, Ryo Lu, hints at what an AI-native company is
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AINov 17, 2025
These days I do not use Expo to build apps
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StartupNov 12, 2025
You need to choose carefully who your product is for
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AINov 6, 2025
1. The smartphone is already one of our organs.
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Data & Decision-MakingNov 2, 2025
While designing a UI where data converges toward the right value over time
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AIOct 30, 2025
As someone trained in computer science and engineering, watching how LLMs are built and work feels beautiful
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Engineering LeadershipOct 29, 2025
My measure of happiness is how many happy people surround me
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HealthOct 26, 2025
The hardest person to help is the one who thinks the problem is just not knowing the right methodology
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HealthOct 21, 2025
"And now these three remain ; exercise, diet and sleep.
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Engineering LeadershipOct 5, 2025
RevenueCat's 2025 App Subscription Report
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Engineering LeadershipOct 2, 2025
What an AI-Native Organization Looks Like
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Video

Engineering LeadershipOct 1, 2025
Sam Altman Takes On Zwift
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AISep 30, 2025
Reusing Reasoning Steps as Behaviors
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Video

Engineering LeadershipSep 25, 2025
What Happens When Builders Stop Thinking Like Users
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AISep 19, 2025
Model = Simulation
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AISep 19, 2025
Can LLMs Make Better VC Decisions Than Humans?
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Engineering LeadershipSep 7, 2025
Yang Zhilin on Managing Teams Like Training AI
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StartupSep 6, 2025
What Successful Founders Usually Say
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AISep 4, 2025
How to Get AI Agents to Write Code
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AISep 3, 2025
Crosby and the AI-First Law Firm
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Engineering LeadershipSep 3, 2025
Cooking Knowledge
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Engineering LeadershipSep 2, 2025
Would I Be Becoming a Better Leader Without Raising Kids?
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Engineering LeadershipAug 28, 2025
Real Problems Take Time
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Engineering LeadershipAug 28, 2025
Elena Verna on AI-Native Company Culture
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AIAug 23, 2025
How LLMs Help Me Win
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AIAug 22, 2025
Why Claude Code Feels Ahead of Other Coding Agents
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Engineering LeadershipAug 21, 2025
Isn't this basically a co-founder?
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AIAug 21, 2025
How should we interview developers now that AI can code?
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AIAug 20, 2025
Something unexpected happened after I opened the Harvest service I built as a hobby in English.
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AIAug 9, 2025
I plugged GPT-5 API into our AI products the day it launched, then turned it off behind a feature flag.
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Engineering LeadershipAug 6, 2025
Some people wave off what looks extraordinary to me as if it were nothing.
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Engineering LeadershipAug 6, 2025
Every time I do context engineering, I think of the senior people I worked with.
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AIJul 26, 2025
Manus creates a todo file when giving an agent a complex task.
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Engineering LeadershipJul 24, 2025
I was reading a summary of Lex Fridman's new Demis Hassabis interview.
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Engineering LeadershipJul 22, 2025
I spent a day vibe coding with Brian Jang from Kakao Ventures.
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AIJul 21, 2025
RevenueCat recently turned down a $500 million acquisition offer and instead raised a Series C at the same valuation.
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Engineering LeadershipJul 20, 2025
I've gotten older too, and I've learned that practice doesn't always bring results.
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Engineering LeadershipJul 20, 2025
How should we build AI products?
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Engineering LeadershipJul 17, 2025
The most loved tools
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Engineering LeadershipJun 2, 2025
In San Francisco, Waymo has already passed Lyft by ride volume and is expected to pass Uber within 12 months.
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HealthMay 15, 2025
High intelligence + high energy + high consistency.
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Engineering LeadershipApr 22, 2025
A good tip for technical docs: explain a single concept three times.
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StartupApr 20, 2025
Every product exists in two contexts.
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StartupApr 12, 2025
AI is the label we use for technology that hasn't quite been realized yet.
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Engineering LeadershipApr 8, 2025
One thing I consider personally important in work and in life is learning to see myself objectively.
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Engineering LeadershipApr 2, 2025
I wrote this eleven years ago. Replace computers with AI agents and it becomes a story about today.
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Engineering LeadershipMar 28, 2025
Working hard vs. working smart
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AIMar 23, 2025
Everything that was possible through remote work can now be done by AI.
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Engineering LeadershipMar 22, 2025
Linux ships on a 9-week release cycle.
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StartupMar 22, 2025
Lately, a lot of founders from Korea have been visiting Silicon Valley.
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Engineering LeadershipMar 21, 2025
What matters most in an interview is making the other person feel, 'I'd want to work with this person.'
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Engineering LeadershipMar 17, 2025
What Seth Godin says is the essence of marketing
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Engineering LeadershipMar 10, 2025
As vibe coding spreads, 2025 has become the first year in which coding is no longer a startup's main bottleneck.
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Engineering LeadershipMar 2, 2025
The surest way to eliminate fear? Do the thing a hundred times.
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Engineering LeadershipFeb 24, 2025
What management really is: saying clearly what is good and what is not.
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StartupFeb 18, 2025
Japan DeNA 2025 AI Day keynote 5-line summary.
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Data & Decision-MakingFeb 15, 2025
Just recognizing that I might be in a bad mood today can help me reduce a lot of mistakes.
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Engineering LeadershipFeb 11, 2025
Differences in internal communication between Korea and the U.S. * Korea: The listener must understand on his or her own.
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HealthFeb 8, 2025
Helping startups begins with walking into their hellfire.
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Engineering LeadershipFeb 5, 2025
Dub: A copy trading app that has become a hot topic among American teenagers * Copy trading: Trading other investors’ portfolios…
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StartupJan 30, 2025
3 ways startup CEOs break up their teams and ruin their businesses.
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AIJan 26, 2025
1. Recently, generative AI, especially LLM (Large
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StartupJan 16, 2025
For about a month, I posted long and short articles on LinkedIn, Threads, Substack, and Facebook.
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StartupJan 14, 2025
Four “rules of the early startup game” that are obvious if you know them, but are expensive if you don’t know them.
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Engineering LeadershipJan 12, 2025
What is leadership?
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StartupJan 7, 2025
The Intro Post I Shared When I Started Working with Kakao Ventures
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AIJan 3, 2025
Types of Sinister Pivots - Andrew Chen 1.
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Engineering LeadershipDec 30, 2024
One way North Korea steals cryptocurrency.
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Engineering LeadershipDec 28, 2024
After leaving Coupang and working at other Korean startups, there was one question I always had.
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Engineering LeadershipDec 26, 2024
“Talent = Good Taste + Bridging Effort” 1.
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Data & Decision-MakingDec 25, 2024
How to measure threaded iOS app performance (Source: Meta Engineering Blog) 1.
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StartupDec 24, 2024
It is not for nothing that people and teams are said to be invested in.
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StartupDec 22, 2024
Product-Market Fit is like, at some point, “Now we’ve got it!” It sounds like it's over, but the truth is...
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Engineering LeadershipDec 21, 2024
User-centered engineering - Improving the user experience should be the goal of engineering.
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AIDec 20, 2024
Changes in the app market: Downloads decrease, profits increase 1.
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Engineering LeadershipDec 19, 2024
1. As a result of analyzing occupational groups in the United States, taxi drivers and
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Engineering LeadershipDec 18, 2024
MIT researchers reveal why legal documents are difficult.
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Engineering LeadershipDec 17, 2024
Analysis of OpenAI's latest failure report OpenAI released a public report on failures that occurred on December 11th.
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AIDec 15, 2024
The AI development stage resembles the leader's delegation expansion stage.
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AIDec 14, 2024
1. The most surprising thing now is that in just 24 months
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Engineering LeadershipDec 12, 2024
If someone is criticizing someone else, be happy to say it.
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Engineering LeadershipDec 11, 2024
This process is the same for not only thesis but also starting a business.
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Engineering LeadershipDec 10, 2024
Japanese web design: strange but effective.
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