Claude Opus 4.6 vs. GPT-5.3 Codex: How I shipped 93,000 lines of code in 5 days

Welcome back to How I A I. I'm Claire Vaux, product leader and AI obsessive here on a mission to help you build better with these new tools. Today, we're gonna bring you up to date on all the new coding model releases from OpenAI and Anthropic. In case you missed it, OpenAI released last week, codecs, their desktop app for AI engineering, the new model GPT five three codecs. Try saying that five times fast. And Anthropic released their response, Opus four six and Opus four six fast. If you're new here, then you don't know. But when these new models come out, I put them through their paces. I test them. I test them side by side on the same task, and and I'm gonna give you my opinion about where they do well, where they fall apart, and which one goes where in my AI engineering stack. Spoiler alert, I've shipped more code in the last five days than I think I have in the last month. So I think these are pretty fabulous models, but they do have their quirks. They do have their strengths, and sometimes they go off the rails. Let's get to it. This episode is brought to you by WorkOS. AI has already changed how we work. Tools are helping teams write better code, analyze customer data, and even handle support tickets automatically. But there's a catch. These tools only work well when they have deep access to company systems. Your Copilot needs to see your entire code base. Your chat bot needs to search across internal docs. And for enterprise buyers, that raises serious security concerns. That's why these apps face intense IT scrutiny from day one. To pass, they need secure authentication, access controls, audit logs, the whole suite of enterprise features. Building all that from scratch, it's a massive lift. That's where WorkOS comes in. WorkOS gives you drop in APIs for enterprise features so your app can become enterprise ready and scale up market faster. Think of it like Stripe for enterprise features. OpenAI, Perplexity, and Cursor are already using Work OS to move faster and meet enterprise demands. Join them and hundreds of other industry leaders at workos.com. Start building today. Okay. To start, I like to pick a task when I'm evaluating new models that's pretty ambitious, something I definitely wouldn't wanna do by hand, and is consistent enough that I can actually compare the pros and cons of each model side by side. And I picked a task that I choose often when comparing these models, which is redesign my marketing site. I think all these models are pretty good at one shotting kind of a landing page or a marketing page, a simple app. I don't feel like that's a practical evaluation criteria for these known models. I like to take a code base that's relatively complex or at least established and compare side by side how these models work inside these code bases. …