Lenny's Podcast: Product | Career | Growth
00:45:01 · Simon Willison
[00:45:01] S0: So I think this is the single biggest shock in all of this. The reason that we have to rethink how we build, how we work as software engineers is that the thing that used to take the time takes way less time. It's never been the case that programmers spend 90% of their typing code into a computer. There's so much additional work around that, but it still used to be... People talk about how important it is not to interrupt your coders. Your coders need to have solid two to four hour blocks of uninterrupted work so they can spin up their mental model and churn out the code. That's changed completely. My programming work, I need two minutes every now and then to prompt my agent about what to do next, and then I can do the other stuff and I can go back. I'm much more interruptable than I used to be. But yeah, so the thing that used to take the time is now the thing that takes way, way less time. What does that mean for everything else that we do? And that doesn't just affect programmers. It affects entire teams around software development. But as an individual programmer, you have to start thinking, okay, I can churn out 10,000 lines of code now in the time that it would take me to write 100. How do I make that code good? How do I make sure that I'm not just churning out total slop that adds up to technical debt that slows me down? How do I take the fact that code is now cheap and use that to produce better code? Because I don't just want cheap code. I want really good code that does what I need it to do that I can extend in the future that's got all of those characteristics of code that's useful and can be used in production.
00:46:35 · Lenny Rachitsky, Simon Willison
[00:46:35] S1: The point you made earlier I think is a really important one along these lines, which is when you start a project, you fire off three different versions of it and that helps you pick a direction. And that's only possible because code is so cheap now, right? [00:46:45] S0: Right. Prototyping is almost free, I think. And that really impacts me because throughout my entire career, my superpower has been prototyping. I've been very quick at knocking out working prototypes of things. I'm the person who can show up at a meeting and say, "Look, here's how it could work." And that was kind of my unique selling point, and that's gone how anyone can do what I could do. But you still have to learn when it's appropriate to prototype, how to think about prototyping, how to get the tools to build useful prototypes that you can use to explore things.
00:47:19 · Lenny Rachitsky
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00:48:33 · Simon Willison
[00:48:33] S0: So right now, I'm mostly Claude. I do a huge amount of work using Claude code. Well, I'm mainly still a Claude Code person, but there are two sides of Claude Code that I use. There's the Claude Code that runs on your computer, and then there's Claude Code for web, which is their hosted version of Claude Code. And I use that one more than the one on my own computer, partly because that's the one you can access through your phone. If you've got the Anthropic Claude app installed on the iPhone, there's a code tab and you can go in there and you can tell it to write you things. And that, it's running on their servers. You need to give it a GitHub repository of yours that it can work within. But it's also great from a security point of view because if you're running Claude code on your laptop, there's risks that bad things can happen. It might accidentally delete things. If I'm running on an Anthropic servers, I couldn't care less. It's their computer, it's not my computer. Go wild. So this means that you can run these things in YOLO mode. Claude calls it dangerously skip permissions. OpenAI actually do call it YOLO. They've got an option for that, and that's the mode where the agent doesn't ask you if it should do something all the time. And that is a different product. I think a lot of people who haven't got on board with coding agents yet haven't tried them in the unsafe mode. They're using the coding agent where it's like, "Oh, can I run this piece of code? Can I edit this file?" And that means you have to pay complete attention to it the whole time, and it's like working with a really frustrating toddler that's constantly nagging you about what... Really frustrating toddler that's constantly nagging you about what it wants to do. The moment you take the safeties off, now I can run four of them and go and have a cup of tea and come back and they've achieved something useful for me, but it's inherently unsafe. If it's running in Claude Code for web, the only bad thing that could happen is maybe it accidentally leaks your private source code. And my code is all open source, so I don't care. That's a useful trick there. But yeah, so I use that on my phone. I often have two or three of those running. A lot of my major projects are done mostly prompting on my phone.
00:50:38 · Simon Willison
If it's security adjacent or super important, I might pull it down to my laptop to do a thorough review later on. But most of the review you can do through GitHub. These things will file pull requests and then you use the same tools you'd use to review code from other people to review the code from the agents. That said, OpenAI came out with GPT 5.4 about three weeks ago. It's very, very, very good. I think it's on par with Claude Opus 4.6, and possibly even better. These companies are constantly leapfrogging each other. So I have been leaning ... It's also cheaper. So I've been leaning on GPT 5.4 a lot more this month, and OpenAI Codex, and OpenAI Codex and Claude Code are almost, almost indistinguishable from each other now. They're both very, very good pieces of software. And I kind of expect this to happen. The next Gemini model comes out might become the best coding model for a couple of months, in which case I might switch myself into that ecosystem. Partly because I write about this stuff as well. I like to stay familiar with as many of the offerings as possible. But I keep on coming back to Claude Code, mainly because it fits my taste. There's this weird thing where I've got a very specific taste in how I like code to work, which coincidentally happens to map to how Claude Code likes to work, which is kind of interesting. And GPT 5.4, it almost matches my taste, but not quite. And maybe that's because I've just spent more time with Claude, so my prompting style has evolved more to fit the Claude way of thinking. I don't know. This stuff's all so weird. It's vibes all the way down.
00:52:07 · Lenny Rachitsky, Simon Willison
[00:52:07] S1: That is so interesting. So, the taste is the code, the quality of the code it puts out is what you're talking about, not like the conversation and the UX. [00:52:14] S0: Absolutely. Don't care about how they talk to me. I'm using them to get stuff done. Yeah. [00:52:19] S1: Yeah. Because I was thinking as you're talking, what is the thing that will get someone to stick with a model? And it could be what you're describing, the way it writes code. It could be the UX, it could be the conversation vibes.