Can Sar (@cansar) profile picture

Codex @OpenAI. Previously: Cash App & Block, YC S17, Google, several startups.

Joined August 2008
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A personal update: I’m joining OpenAI to work on Codex, the best agent app in the industry. After years building consumer products, my obsession since September has been to make Block one of the most AI-native engineering orgs in the world. I’m proud of what we’ve built: faster Eng velocity with RPI in October, an internal multi-harness ADE in January, Slack-based cloud agents in February, and AI woven into every step of product development. The team is just getting started. Along the way I tried almost every agent orchestrator out there — 30+ over the past year. Codex felt special from the day it launched. Lately, it’s started to point at something much bigger. What used to be scattered across prompts, tabs, tools, files, and handoffs is starting to come together in one place. The app is becoming the single surface for knowledge work — letting you accomplish more than you ever thought possible, while staying calm and focused. You can already see the early signs: making a slideshow and editing it right there, working inside a custom site built just for you and your team, handing off to the browser and the computer while you watch it go. Getting this right takes powerful models. But it also takes taste, product thinking, and real care for the person on the other end. You see that in the product, and you feel it the moment you talk to the team. I couldn’t be more excited to join the Codex team. Together we’re going to build the future of computing and knowledge work, and we’re going to build it for you.
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This escalated quickly.
Putting Can on the list of best names to name your child
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Feeling Cloud-y.
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🤯
Day 25/ We are doubling all usage limits for all Pro 100/200/500 tiers and Business Premium, effective today. We heard your kind feedback and won’t be reducing usage limits for Pro 200, so your Work and Codex usage will stay the same. We’re also going to continue offering extended limits for dots for now, and usage of your dot will still continue to be separate from your default usage. And we'll of course also keep shipping better models and other efficiency improvements that increase your effective usage over time.
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I’m a bit biased here but yeah. Also Thorsten & Co are some of the best in the space.
People have been saying this for a year now. Beware of the great rug pull, etc. But all indications point towards price/intelligence dropping. Ant's S-1 says subs are 10% of rev. Inference has 80% margins. Why should this happen?
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"The iPhone Duo feels like a first gen product that needs more polish."
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I hear we’ll be launching some big things today. Among that, we’re also launching 2 tiny bits of polish I’m really excited about (and added over the weekend). Just 2 of many hundreds, but that’s how you build a great experience. Nothing is perfect on Day 1, but we always try to get there ASAP.
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Tuesday is Dev Day! Excited to see many of you there!
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I first hooked up ChatGPT to voice via @viticci's S-GPT back in April of 2023 and used it constantly. This is another big step on the journey to voice for everything. Excited for the future ones.
Just went for a long walk while using ChatGPT Voice with plugins on my phone, and I think it's a more consequential update than it might seem at first glance. On my walk, I talked through my calendar, email, and to-do list. I had ChatGPT read through my emails and triage them. Then, we added items to my to-do list. Then, we reviewed my calendar. By the end of the walk, I'd finished getting organized, and never had to look at a screen once. I've been waiting for this a long time. Yes, you can kind of do this in the ChatGPT desktop app. And I think in Codex remote on the mobile app. But I've never gotten either to work very smoothly or reliably. And I often want to do this when I'm not near my laptop, like when I'm out for a walk, and the ChatGPT desktop app for whatever reason won't connect. This feels like the future. It feels like a true assistant. You have a natural conversation, and it does stuff for you. It disappears into the background. You're not walking down the street with a screen in your face. You're not contorting your thumbs to type sentences and scroll menus. You're just talking, conversationally, and stuff's getting done. My sense is: • Screens are going away for many uses other than visual content consumption. They won't disappear entirely. But they also won't dominate the way they do now, and definitely not for things that can be done verbally. • Apps that aren't agent-native and plugin-optimized will die. I use Google Workspace and Todoist primarily because they're so well-integrated with ChatGPT. I stopped using apps, such as many of Apple's, because with few exceptions they're poorly agent-integrated. (X is a big exception, but I've hacked some integration via IFTTT.) • Those apps, however, will become more valued for what they let agents do than for their in-app experiences. Not all will become essentially databases, but many will. It also seems inevitable to me that at some point OpenAI and other AI app providers roll out native calendar, email, and to-do functionality that's maximally agent-optimized. • We'll have our audio agents on all the time. We may have them on mute sometimes (I discovered you can do this with ChatGPT Voice by clicking an AirPod), but at great cost, because you'll want be able to just say something like "summarize that conversation I just had and then draft the presentation." It will be like having an assistant following you around when you want them to. • We need new hardware. For example, I want a camera in my AirPods not to take pictures, but to have the context of what's around me. Like, "What kind of tree is that?" Or, "That's a cool shirt. Find out where they bought it." (I have this in my Meta Ray-Bans, but people are now very sensitive to those devices because they do take pictures.) I also want ChatGPT able to be always listening or awoken with "hey, Chat." • The individual thread model starts to break down when you're treating ChatGPT like an always-on assistant. We need to have the infinite continuous thread from which ChatGPT can delegate work to subthreads, the central assistant model that Muse is built around. This makes even more sense when you start treating your AI apps like assistants. They should be juggling all those individual threads on your behalf. More to come I'm sure as I continue to experiment.
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Codex users: What kind of projects & repos do you usually work with? Large / Small? Established / New? Many / Few? Want to understand this more broadly.
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People are somehow still arguing about whether AI is or will be a big deal, huh?
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Replying to @TheZvi
@TheZvi Greatly appreciated today’s B5 reference. Used to have that quote as a Win 95 sound effect back in the day (for emptying the trash maybe?). Thank you for your service.
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I’m maybe biased now but I had this take before too. Don’t be reckless with tokens, but don’t overthink it either.
It's hard to justify using models that are dumber than Fable and Astra. For real-world code work, the benefits massively outweigh the cost. The benefit isn't better code, it's something else that's more subtle.
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Housing is good.
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Realized that I never upgraded to Tahoe on my personal machine because I've been too busy to use it the last year 🙃 Just installed it (need XCode for something) and saw the new Safari. It's certainly something...
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One of the greats
Today is my last day at @CashApp. A very bittersweet moment. I’ve truly loved the past ~6 years here. Such a great team and deeply positive impact on so many customers’ lives. I now have a deeper respect for @jack than I did on day one and believe the future of @blocks can and will be amazing. I’ve learned so much from, and will deeply miss, the people here. Will share what’s next for me in a couple of weeks. 💚
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Welcome Apple to the foldable phone game. Nokia got here in 1996 ;P en.wikipedia.org/wiki/Nokia_…
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Convincing people that AI could transform coding was so big (and challenging!) in Q4 of 2025. That changed pretty quick in January. At Block we heavily (...) prioritized doing the same for all functions, but even so that takes a while. I think we have some things that are going to help a lot here.
I'm thankful this turned out to be wrong and the vast majority of prestigious devs have started embracing AI for code. Does that make things a little more embarrassing for the ones who don't, though.
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In Q4 of 2025 I led a big push to teach Block engineers advanced context engineering to get the most out of Claude Code & Co. In March/April we started switching to Codex in large numbers. With 5.4 and especially 5.5 it could solve problems and build things that other tools could not. But my favorite was how good it was at compaction - instead of all the fancy sub-agent tricks and intentional compaction you could just keep going and going. I had 1 thread that built a whole sync protocol, server, and client, across multiple repos & languages, and also deployed them. Since then compaction continues to get better and better. Monothreads are a common topic now, but I'm still surprised by how much you can do in one thread without any issues.
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I'm engaging with you as a human being.
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