
@ccheever.com on 🦋/ working on @expo & @castlexyz
Palo Alto, CA
Joined April 2007
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This seems intuitively ~ right to me
Compaction is a mistake.
When an agent's context fills up, tools like Codex and Claude Code compact it:
1. The model prefills the entire session again
2. It writes a summary of everything so far
3. A new session starts from that summary
I measured this on a real ~400k-token session with Opus 5.5:
→ 38 s and $1.99 when the prompt cache has expired
→ 29 s and $0.17 when it hasn't
And the summary is lossy. The exact error message, the file path, the one number you needed is often gone.
So I do something new for Mainplane
Context retrieval works the other way around. Mainplane keeps the full record of every session as a file. When the context fills up, a new session starts right away with one instruction: "You are continuing session X. Retrieve key context from it as you go."
The agent searches the old session and copies the exact lines it needs, when it needs them.
Same session, same model: 15 s and $0.10 to get back to work. It does not depend on a cache hit, and nothing is paraphrased.
This is the bitter lesson applied to agent memory. Don't hand-design what the model should remember. Give it the full record and good tools, and let it decide.
Mainplane is open source (MIT). Link in the first comment.
Charlie Cheever retweeted
If you need help with anything -- mobile, web, agentic transformation work, reach out -- I still have a couple great teams available! jamon at infinite dot red
Charlie Cheever retweeted
Fifty years of C and we're still shipping buffer overflows.
Aristotle proves your C does what you said it should. When it doesn't, you get the input that breaks it.
New sign-ups get $500 in credits. Get started with the most effective way to protect your enterprise:
aristotle.harmonic.fun/?r=x
Charlie Cheever retweeted
.@expo Simulators to the rescue! Super useful if you want to scale your mobile validation loops for agents above what's currently possible with physical Macs you own (or if you don't have Macs) 🚀 We are here to help 🙌
expo.dev/services/simulators
It is funny that the #1 thing I'm remembered for making these days is bunny1/lolbunny which I made in 3 hours on a Friday night when I didn't have plans.
Replying to @G_Moskaliuk
It would be good to write a blog post on reactnative.dev that summarizes the total effect of all your work. I suspect the improvements are substantial enough that performance comparisons against older releases of RN are invalid. Thank you for your contributions!
Charlie Cheever retweeted
Genuinely never could have imagined T3 Code getting as massive and well loved as it is today. Thank you all. Never giving up on open source 🫡
Charlie Cheever retweeted
I was tired of agents building React Native screens without an easy way for me to see what they were building (i used to either run simulators or hook up my phone with argent). It's such a slow cycle time for active development.
So I used Expo Web to put my app’s real screens and states on a local canvas.
Now I can see the flows and steer the work. i thought i was already going fast, just you wait
Look, We just shipped App Intents in the @IcehouseVenture app, built with @expo.
You can now search your IV portfolio and open funds right from Spotlight. Or just ask Siri.
"Open Substack in Icehouse Ventures" 👀
Isn’t cool!!
Charlie Cheever retweeted
We’re bringing Aristotle to code.
AI is writing more code than anyone can review. We're building the AI that verifies it.
Starting today with C and Verilog.
Charlie Cheever retweeted
Starting today, Aristotle can verify C code including ~~memory safety~~, and control- and data-path properties of Verilog designs! We’ve started with bytes and electrons, and this is just the first step on our path to making all software and hardware verified by default.
Well, soon there’ll be one for iOS, Android, and Web. 100% built with @expo. @wcandillon I can’t describe how much I love WebGPU. It’s a game changer. Crazy what I could pull off in such a short time. Super smooth even in debug mode (even better in release).
Charlie Cheever retweeted
Some of these numbers are truly surreal. Almost $5m/day in tokens going through T3 Code 🤯
Almost at 750,000 installations. 100k DAUs will be hit this week.
Charlie Cheever retweeted
I finally made my dream Lego app!
◆ Super fast: 2.8x faster, 67x smaller JS heap
◆ Interactive instructions
◆ Sculpture generation
◆ AR previews on iOS
◆ Physics engine running in a worker
◆ Completely free!
Try it now:
lego.bacon.md
Charlie Cheever retweeted
This is completely unacceptable.
Civilians are dying because of Donald Trump and Elon Musk’s decisions.
Americans do not support abandoning the people of Ukraine under Russian attack.
JUST IN: Ukrainian President Volodymyr Zelenskyy told ABC News on Friday that the Starlink network is still not working, despite assurances from President Trump. abcnews.link/mlqG7V3

























