Mark.

Member of Technical Staff @a____t____g
9x hackathon winner
SF

[Mark. @markmdev]

A month ago my Codex setup had 100 skills. Today it has 62, and the total instruction volume across them dropped by half in the last two weeks. Those cuts used to be judgment calls. This week I turned them into measurements.

The method is simple: each rule in my AGENTS.md gets a realistic task where the natural shortcut violates exactly that rule, and then the same task runs again with the file unloaded. If the agent behaves correctly both ways, the rule is a model default and the line is dead weight. That was the outcome for 10 of the 17 rules I tested. The four rules that actually changed behavior were the ones that make my setup mine: reading project memory before working, updating it after, stopping when a plan assumption breaks mid-task, and gating design decisions. And one rule failed every attempt no matter how I worded it, which taught me more than the passes did.

Full method and results in the article.

[Mark. @markmdev]

https://t.co/ElQWe2tf9b

[Mark. @markmdev]

@oscrhong @instinct @bot @Muse @uncanny_guzus @dflieb This is amazing!

[Oscar Hong @oscrhong]

we built “let’s bump phones to exchange contacts” but for agents!

now your @instinct / @bot / @muse (whatever you use!) can make plans, negotiate deals, and get what it needs from your friends/coworkers’ assistants

it's “have your ppl (agents) talk to my ppl (agents)!” for everyone 🤝

built w/ @uncanny_guzus @ @ycombinator #MakeSomethingAgents hackathon (s/o @nemild)

on top of @stripe (agentic p2p payments) + @manufact (mcp relay server) 🙌

Who will you bump first?

[Jacob Coxon @hilbertspaess]

I resigned from Anthropic today. I spent the last three years doing pretraining research at both OpenAI and Anthropic. Neither company is acting responsibly. They are racing straight to self-improving superintelligence and gambling with our lives. More thoughts below.

[OpenAI @OpenAI]

This is GPT-6 Astra.

Anything you can do on a computer, Astra can do for you. Fast.

[Mark. @markmdev]

@MatthewBerman @bot 👋��

[Sharif Shameem @sharifshameem]

i'll never forget that time someone demo’ed me a language model at a hackathon in 2022 and I thought to myself "this is just GPT-3 but worse"

and it turned out to be Claude 1

[Javokhir @_javokhir]

WE RESEARCHED ALL 6,077 YC STARTUPS

We wanted to know: do these startups share anything in common? And how have trends shifted over time?
Here's what we found:

[Mark. @markmdev]

You got claudex. But do you have fabledex?
https://t.co/lJxrYp8uLj

[Mark. @markmdev]

@oscrhong @_javokhir 🔥

[Oscar Hong @oscrhong]

WHERE ARE YC FOUNDERS NOW?

@_javokhir and I were curious where they go "after the startup". So we ran Deep Research on ALL 11,398 founders who have ever gone through YC.

Here's what we learned: joinedanthropic dot com

[Mark. @markmdev]

If Codex repeatedly reconnects after you send a message or takes 15+ seconds before it starts responding, check whether the task has accumulated lots of screenshots. In my case, completed compactions retained raw base64 image payloads, causing later turns to repeatedly process a huge image-heavy history.

Removing those retained image nodes restored 4-8s response times. I packaged the repair for this specific symptom as a skill:
https://t.co/mb8l4UXdVd (Just send it to your Codex if you hit the same error)

[Mark. @markmdev]

Why is nobody talking about this Codex feature?

You can select anything in the agent's response, click "More details", and
it creates a new ChatGPT chat that already has all the context and just
explains the thing to you.

It helps so much when you don't understand something in Codex's answer.
Before, I'd open a side chat, write a prompt, and wait while it
double-checks everything it already knows. Now it's one click, and the
explanation is almost instant.

And it's not just about code either. If you're learning something new, just
use it all the time. It's extremely powerful.

[Javokhir @_javokhir]

I embedded all ~6,000 launched Y Combinator companies by what they actually do, and mapped idea-space.

[Mark. @markmdev]

https://t.co/ElQWe2tf9b

[Mark. @markmdev]

@jxnlco 🙌🏻

[Mark. @markmdev]

Attending AI Engineer World's Fair this week.

My Day 1 saved sessions lean coding agents / AI-native SDLC: Codex, Uber uReview, 1M AI-generated PRs, production code access, Claude long-horizon, Shopify River, Figma, Cursor.

If you're there too, what are you prioritizing?

[Mark. @markmdev]

@annkur @reach_vb $200 Pro plan