designing interfaces for humans and agents @fastreplinc | yc alum
Seoul & SF
Joined November 2021
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John Jeong retweeted
As a builder in the AI video space, I was terrified about how much markup API providers charge for simply routing the models.
Higgsfield API adds a 40% markup even with its maximum advertised discount. Fal adds 100%. Runway adds 414% (Seedance 2 480p)
I might be hated by the industry, but :
Today, we’re launching Sume API, the first image & video model provider with 0% markup.
For example with Seedance 2.5 1080p
• 50% cheaper than fal
• 50% cheaper than higgsfield api (29% even with biggest discount)
• 28.02% cheaper than kie ai
The routing infrastructure layer is never the moat. We believe that APIs should be commoditized, and the moats will be built at the application layer.
Check the pricing comparisons below, and see how the broken industry is saved.
John Jeong retweeted
Introducing Tamagui 3.
Now the fastest and highest coverage Tailwind style library there is, free or paid.
Tamagui is now 100% open source, I’ve made Takeout and Bento OSS as well.
A rewritten compiler in rust now makes native even faster, plus a new C++ native runtime avoids re-rendering.
Flat style props, React Strict DOM, and a web-alignment push make Tamagui easier, lighter, and more familiar than ever.
tamagui.dev/blog/version-thr…
John Jeong retweeted
Linear CEO @karrisaarinen: "I took a break this summer from paying attention to AI. I thought that when I came back, I'd feel left behind. But when I came back, I realized that nothing has really changed.
There's new models, there's new techniques, there's new agents. But in the end, making great products, increasing revenue, and building the business—it's still hard.
It's clear the tools are getting better, you can do more, you can do it faster. But I think the more important question is: are we actually making better things with these tools? Are our teams getting better with these tools?
I don't think that answer is clearly yes.
There's a lot of emphasis now on toolmaking and using tools and building systems. But I think in the end, as product people, our job is to make something great."
John Jeong retweeted
if you’re a venture backed founder, you should be 100x more ambitious & risk seeking than you think you should be.
i’ve unfortunately made this mistake constantly. your brain naturally wants to take the next logical step & you obviously fight that instinct because you have to. so naturally you end up at like 10x.
but 10x is still more than likely extrapolation of existing trends. if you want to end up somewhere genuinely far ahead you have to think 100x while still making sure what you’re up to is familiar & relatable. very difficult multi dimensional problem all around.
John Jeong retweeted
My daughter is 3 months old.
She'll grow up calling out attacks to her Pokémon like Misty, in real time.
Here's what I built with Opus 5.5:
- Took Pokemon Emerald Arena from @germanburgardt
- Whisper on-device (~250 ms)
- @typesafeai Jev picks the move (~250 ms)
(sound on)
John Jeong retweeted
It’s also just isolating - even earliest employees can’t truly empathize or understand the pressures and responsibility.
John Jeong retweeted
Space and time reconstructed in 4D
Is this how higher dimensional beings see us - every moment at once?
Starting to understand what Vonnegut meant by humans being “great millipedes” - clearly it applies to our four legged friends too!
Geolocated 2d video → per frame 3d gaussians → each left precisely where & when it happened
John Jeong retweeted
we're hiring engineers of @AsideAI
$160k-300k + significant equity, in-person SF
we're growing crazy fast (25% WoW) and now building v2
join us if you wanna build the harness from the ground up (memory, computer use, compaction, agent loop) and compete with frontier labs
John Jeong retweeted
Through the VOICE trial, Terry is using his Neuralink implant to help fine-tune a brain-to-voice interface for himself and others who can’t speak. He trained the algorithm first by miming speech as best he could, then by simply thinking the words and hearing them come out in his own natural voice.
Powered by Grok Voice from @spacexai
John Jeong retweeted
Nari Labs' Qwen3-TTS and Qwen3-ASR endpoints lead @covaldev voice AI benchmarks 🎉
Text-to-Speech
> #1 Lowest Latency (time-to-final-segment): 44 ms
> #2 Accuracy: 3.6% WER, just 0.1% shy of #1
Speech-to-Text
> #1 Accuracy: 3.8% WER
> #2 Lowest Latency (time-to-first-audio): 63 ms
Read more: narilabs.com/blog/nari-labs-…
John Jeong retweeted
Best shi have played in a while doodleshooter.vercel.app
John Jeong retweeted
Numbers software designers should know
8.3 ms = one frame at 120 Hz
16.7 ms = one frame at 60 Hz.
100 ms = response feels instantaneous
200–300 ms = transitions feel snappy
300–500 ms = transitions feel deliberate
1 second = delay interrupts thought
10 seconds = waiting loses attention
44 × 44 pt = comfortable minimum touch target
4.5:1 = minimum contrast for ordinary text
3:1 = minimum contrast for large text
45–90 characters = comfortable body line length
1.2–1.45× font size = comfortable body line height
John Jeong retweeted
We have been building an iOS app in stealth and we just hit private beta today!
> Life-like voices running on your iPhone
> Listen to anything: Books, PDFs, articles, emails...
> Works offline as you commute or travel
Beta testers who submit feedback will get a free lifetime license. DM me if you want an invite.
John Jeong retweeted
one of my hot takes is that nyc is one of the worst places to build consumer apps.
founders there tend to overfit to extremely specific nyc behaviors: making lists of places to go, restaurant reservations, coordinating plans, etc.
sf is substantially better, and the outcomes prove it. nyc has produced surprisingly few (zero?) generational consumer software companies. sf has produced so many that many individual companies are worth more than all of nyc consumer tech combined.