Claude Code with Sonnet 4.5 is actually incredible (with 1 exception)

Claude Sonnet 4. 5 just came out. Anthropic has made some mindblowing promises with it. They are saying not only is it the best coding model ever released, but it can also code by itself for 30 hours straight. I'm about to put that to the test. We are going to find out once and for all if Anthropic is lying to us. We're going to build a full scale, full stack application using Claude Code and Sonnet 45. By the end of this video, not only will you know if Sonnet 45 inside Claude Code lives up to the hype, but you also learn a ton, too. We're going to be building a full stack prompt library application with database, AI, authentication, all the above. We're going to give it to Sonic to build out and you'll actually have, if you follow along with me, a really cool application you can use every day.

So, right now I'm in Visual Studio. I have the Claude Code extension opened up and installed. Yesterday we covered all of Sonnet 45 in the big release. Anthropic has made some huge promises. Let's see how well they do here. We're going to be testing out this Claude Code extension as well. This is something they newly released. I couldn't get it working in cursor, but I got it working inside Visual Studio. I'll have a link down in Visual Studio if you want that. Free to download, really easy to set up and install. We have that up in here, and let's start building our app. Here is the prompt we're going to be using.

Feel free to take it from the description down below and build along with me because if you do, you'll have a really awesome app you can use day-to-day as well. I want to build an AI prompt library app. Users can enter in an AI prompt and save it to their library. They can view their library of prompts and edit them. The prompt editor should be a beautiful markdown editor. There should even be a button in the editor called optimize that takes the prompt and sends it to Claude Sonnet 45 API and optimizes the prompt to improve it. This should be a beautiful application using Tailwind and Shad CNN. It should be Nex. js and Superbase for database and off. Get creative with the UI. Don't make it a basic AI interface. So, we're going to build an awesome application full stack. So, have database off AI everything you need for a fullscale application. So, you're going to learn a ton of and have an awesome app. Let's hit enter on this. Let's put it to work. So when I typically use Claude Sonnet for Opus 4. 1, I'd break it down into small little tasks, make it easy to build out. It was great with building those tasks out little step by little step. But with Sonnet 45, Anthropics telling us it can work for 30 hours straight on code. So I gave it the full monty. prompt. So let's see if we can just build it out in one shot here. So it built out its to-dos here. I'll make this a little bit bigger for you guys so you can see this. So, it's going to build out the application, add all the technology, do I want to allow this command? Yes, and don't ask again. And we'll get to work here. We're using Nex. js for the front end. Really simple to use web framework. We are going to use Superbase for the database. I'll show you how to set up that as well for both the database and the O. And we'll see if Anthropic will come through on their promise here on this being the best coding model ever. I'll be honest with you, over the last few weeks, codeex with GPT5 has been incredible. Let's see if Anthropic took the lead once again. So now it is installing the visual components. It is installing Shad CN which is a really nice visual library for Nex. js. So it's going to look hopefully not like an AI application. Look more like a beautiful project. You want to make sure you use Tailwind and Shad CN for your projects cuz if you just tell the AI, hey buildown application, it will always have that really ugly blue and purple, I don't even know what to call it, that gradient disgust that every AI application has. So make sure you do it this way. I honestly trust Claude a ton. So, I say yes and don't ask again for almost everything it says because honestly, it's never really messed up for me. A lot of people complaining the last few weeks that Claude's gone stupider. I'm gonna be honest, I haven't seen that. That hasn't been my experience, but we'll see how Claude code does here with 45. So, it's setting up the Superbase client. So, that's the all the database stuff. I'll show you how to get all these keys as well. We're also going to be using the anthropic API. So, the Sonnet 45 API. So, you're also going to learn if you don't know yet how to use AI APIs. you're building a fullscale AI application here. So, you're going to have a really, really cool and helpful app by the end of this. I do like the Clawed Code extension they have here. Uh, the UI is a lot nicer, a lot smoother, a lot better than the CLI. I'm going to be using the extension moving forward. All right. So, now it's building the authentication pages. It's going to build the prompt library page with the card layout. It's going to have a beautiful editor. If it can pull this off in one prompt, I don't think I ever got sonnet four or three five to do something like this. So, if it can pull this off in one prompt, work and look nice, that'll be amazing. I'll be I'll say Anthropic is back if it can do this. As this is going, by the way, leave a like if you want more Claude code tutorials like this. That's how I know you guys like this content. I'll also be coming out with a video in the next couple days as well on how to build an application with the new Claude agent SDK. I've been playing around with that and let me tell you, uh, it's actually really, really cool. So, make sure to subscribe for that as well. Looks like it is now building the beautiful markdown editor. That's great. It's going to have the prompt creation editing functional. So, you'll be able to save prompts to the database. I'll walk through all that as well. And then the AI integration. I'm really excited to see what the UI is going to look like on this one. I'm going to be honest. I haven't been impressed by any AI models ability to create UI on by itself. Even GPT5, I really didn't like the UI. So, it's going to be a really nice test to see how the UI turns out when it's done this to-do list. From a speed perspective, I'd say this is actually faster than Claude Sonnet 4. Definitely Opus 4. 1. We're already 80% way done building this application and it's only been a couple minutes here. So, if it can build this full scale, like this is an app people pay for. People pay for these type applications and we could potentially have it done in just a couple minutes here. As this is going, I probably won't do too much of a deep dive on kind of the just prompting the AI chatbot on claude. ai, but my tests over the last 24 hours have been rock solid. I really like the way that Claude communicates with you and gives you information on claude. a, just a regular chatbot. I'd say compared to GPT5, I actually like the vibes better. Like vibes are a big thing with AI. And the vibe test, it passes with flying color. So, I actually really do like Sonnet 45 inside Claude's chatbot on Claude. AI. All right, looks like it's all done. Honestly, does it give you a timer? No. But it only took a couple minutes. That was extremely fast. Uh, I've built your prompt library. Here's what's been created. So, the entire structure, the library, markdown editor. Okay, everything we asked for. Let's do this. Let's get the backend set up. So, I'll show you how to set up the Superbase backend. We'll get that set up. We'll put in the AI API key. Then, we'll see what this puppy looks like. We'll get We're only a couple of minutes away from seeing how good this app looks. Let me just quickly walk you through setting up the back end. So, if

you go to superbase. com, I'll put the link down below as well. You sign up. Free to use, very generous free tier with Superbase. It is a very easy to use database you can include in any of your applications. All the AIS are really good with working with it. Set up an organization. Then from there, we want to create a project in your organization. So I'm setting up this new project. You should have an option for a free comput right here. Make sure you choose the free one. I'm going to generate a password for it automatically. And then I'm going to create the new project. By the way, if you're already a superbase master, you can look at the chapters down below and skip to the next chapter. Uh but I'll quickly show how to set this up. For this project, we're going to need the URL as well as the anon key. When you created your new project, if you just scroll down, you can see here the project URL as well as the API key. You can just copy and paste both of these in. You just into your enenv. local file that the AI created for you. And then the last thing we're going to do is just take this anthropic API key, which is very easy to set up as well. You hit save on this. Next thing you're going to want to do is set up the schema for the database. So basically the structure of how the data is saved. It should create a superbase schema file for you. You just click on that, you copy everything that's inside that file. And then in Superbase, you go to the SQL editor on the left hand side, you paste it in, you hit run on that, and then success. No rows returned. That's beautiful. That's exactly what you want to see. You can go to the table editor and you can see your table setup that was just created for you. That's your database is set up. Congratulations. The last thing we're going to set up is going to be the anthropic API key so that our project has AI functionality. I'll show you how

to set that up. Now, if you go to claude. com/platform/api, you can click on start building. From here, you can click get an API key and then you can click create key. Now, we just got to name it. We'll call this prompt library. We'll hit add and that will give you a key you can copy and paste. Copy that in. Paste that to your. env. local file, which should have a space called anthropic API key. Hit save. Your database is set up. Your AI is set up. You're good to go. Let's see how this

app looks. All right, I pull this over. Let's see how we're looking here. The signin screen is the same old ugly purple and blue gradient. Why? What did the AIS do? What are What were they trained on where everything they build is purple and blue gradients? Why? I need to know. What's going to be the sonnet that doesn't have the purple and blue gradients? Are we going to have to go to Sonnet 10 to get the non-purp gradients? What are we going to have to do here anyway? Let's sign up. Let's get this tested. Let's create the account. I'm going to sign up here. All right, we're in. Look at this. Still horrible UI. Still the same old blue and purple gradient. Whatever. All right, let's see how this works. Let's see if the functionality works, though. All right, so we have our live search prompts. You can do new prompt. Sign out. Let's create a new prompt. Let's see what this editor looks like. All right, takes us to this new screen. Very nice. Let's see a title. Let's save the prompt that created this actual application. And so prompt library prompt description builds a prompt library app. This is actually really sick app for all you guys to build as well. I think this could be really helpful when you do your own test with AI or if you build really cool stuff with AI. You want to save the prompt so you can reuse them over and over again. So this is going to be a really cool way to do that. So it's a good project to follow along with me here if you haven't done that yet. Tag this. We'll call this coding. All right. Now let's put in the prompt here. Let's save the prompt. Let's paste in the prompt here. Okay. Is there anything else we want to do? Oh, let's optimize this. All right. Let's test out the AI functionality. So, this optimize button should take our prompt, send it to Claude Sonnet 45 through the API, then optimize our prompt for us to make it even better. Let's optimize it. Here we go. All right. Looks like it came back. Let's see what we got here. Project brief. Okay, so it broke it down into sections, which is I think best prompting uh practices, which I never really do because I'm extremely lazy. So this will actually be helpful tool because it will take away my laziness when it comes to prompting. So that's good. Project brief AI prompt library application core features uh prompt. Man, I almost want to test this prompt. Maybe in the next video I test this optimize prompt to see if the application comes out better. Advanced markdown. All right, so it has goes into way more detail. This is actually sick. Implement thoughtful micro interactions animations. Yeah, this would have looked way better. better if I had this uh prompt library optimizer. I'm actually going to use this app. app I'm building in this video for everything I do moving forward. I cannot recommend enough you guys actually build this out with me and use this because this is actually going to improve my prompting so much. Uh has all the deliverables, additional considerations. This is sick. All right, now let's test out the database. Let's save this prompt here. Let's see what happens. Okay, boom. Look at that. So, it's saved there. Let's check our database out. I'm going to move this over here. Let's open up prompts. And then boom, there it is. A new row in our database. When you make your first application with a database and you set it up and you refresh and you see your first row saved from your application, it is the coolest feeling ever. I miss the feeling of being a new developer because the little feelings like that when you set up your first database is the coolest stuff ever. Anyway, it got the row in there. Got the content, the title, the description. Didn't save the tags. That's the first negative we've seen here. For some reason, the tag didn't get saved, but we can fix that easily. Um, actually, let's debug that now. Let's do a quick debug. Looks like the tags didn't get saved. So, let's go back in and let's edit this to make sure there's no tags in there. Now, edit. Yeah, so the tags didn't get saved. Oh, you know what? I didn't hit add. Let's do that. That's the issue. I didn't see the add button all the way to the right. So, let's do that. Let's do coding. Hit add. Okay, so that's saved there. Now, let's go. Let's save these changes and see if that tag gets saved there. So I come in here. Oh, it already there. Coding. It's already there. Boom. That worked. Okay. And then you can see it there. I do like this again with the purple and blue gradient. Let's favorite this. That's favored. Is there like a favored column in here? So for those new to databases, you got your rows, you got your columns. The rows is the piece of data. The columns is each variable inside your piece of data. Uh oh. Is favored? There it is. Let's refresh. See if that turns to true. Is favorite true? Okay, so that works. Everything. So it set up the database in one go. authentication AI in one go. It set up the functionality in one go pretty flawlessly. It did it very fast. I'd say it's faster than Opus 41 for sure. I'm going to be honest. I haven't used Sonnet 4 in a while. I've only been using Opus exclusively because it's the better model. This is much faster than that. Let's do a couple more tests here. Let's see if we can improve this UI and see how it does with taste. Uh and then we'll do kind of a final review and wrap up here to see what we think. So, let's

go in here. I'm going to say the app works great, but the UI stinks. It looks like every other AI app ever made with the blue and purple gradient. Let's give this a really sharp black and white dark theme with bold lines and a cool feel overall, including animations that make the app awesome to use. All right, so I'm going to give it a little bit of creativity here. Uh, I'm going to say I want it black and white. I want one of those really sharp kind of shaden looking UIs, but I also want to give it a little creativity. So, let's see what it does here. Again, this is what the old UI looks like. Every other A app ever made looks just like this. Functionality perspective. But let's see what it can do here from a creativity perspective. Can it clean up this UI and make it a look a lot better? Give it some animations, make it sharp, modern. I want to see what it does here. So, it's going through, it's swapping out different UI components to, I guess, more modern new ones. I guess unfortunately it's it oneshot the functionality of the app really well, but it can't I guess chew gum and walk at the same time and make a really nice UI. I guess if I did the more optimized prompt that had a lot more detail, it probably could pull it off. But for me, like my test of intelligence when it comes to a lot of these AI models is like how crappy can my prompt be and it still creates amazing results. This again, the app was amazing, but the UI was still kind of that bland stuff. Like I can't wait till the day where the AI has such good taste where I don't have to sit there and say, "Hey, don't make this crappy and it still makes a really good UI. " That's going to be a very exciting day. Clearly, we're not there yet, but let's see if it can make a better UI here. Just as you guys are watching, this is building out the UI. This is going to be a crazy two weeks. I got plenty of more Claude videos testing out Sonnet in different ways these next few days, including the agent SDK. I think I'm going to do a prompt master class with Claude Sonnet. And then next week I'm going to the Open AI Dev Day, which I think is Tuesday in San Francisco. That's going to be really exciting. I'm going to be there firsthand to see all the talks, announcements, everything like that. So, I'm excited to bring you all the news straight from OpenAI Dev Day as well. It is the best time ever to be a tech nerd. It really is. It's unbelievable. Also, in about 15 minutes from this time of filming, I am going to a sunglass hut to get the Meta Ray-B band displays. So, I'm really excited for I am just a tech junkie. I need every new thing when it comes out. So, I don't know. Do I do a Meta Ray-B band display review? Are people interested in that? Let me know down below. Including if you're not interested whatsoever. All right. Looks like it's done. New design system. Let's see how this looks. So, I'm going to pull this over. Uh, interesting. Okay. So, it's like kind of gray and off-white creamy a little bit. I don't hate it. I like it better than the last one. Edit uh is not very It's not the dark theme I asked for. And also, the contrast kind of stinks. You can't really see where the inputs are. Uh this doesn't What does the preview button do here? Oh, okay. Um so, yeah. I mean, does it look better? I'd say maybe marginally. I mean, it doesn't have the blue and purple. Uh, but it doesn't look incredible. Let's favorite this to see what the favorite. Yeah. So, I mean

from a taste perspective, still it's solid. It's not great, but I mean, overall, it oneshot this entire application. And this just was this wasn't just a todo list notetaking app. This was actually a really nice, helpful, cool application. It's a prompt library, right? People are spending tons of money on prompt library apps. We built our own. And it even optimizes your prompts. So, this is actually something I'm going to use on a day-to-day basis. I might even put this live. Should I just put this live for free? If you guys want to live for free, I mean, you can build it yourself. That's free as well. Let me know down below as well. Uh, I could probably sit here and prompt a few more times to fix up this UI a little bit. It's not bad, but I mean, it's also not good. Like, if I saw this online, I probably wouldn't buy the product. With all that being said, it oneshot a lot of really cool functionality, right? It one shot author, it one shot the database. AI optimizing. It one shot the markdown editor. It one shot all of that. And that is really impressive. It also did it in pretty quick time. I think overall it just took 3 minutes for all the functionality to go through. So is it better than Opus for one? I'd say with 100% certainty it is. I mean this is including all the testing I've been doing the last 24 hours. I'd say with certainty this is a pretty sizable upgrade over Opus 41. Not only because I think it's a better coder, but also significantly faster. Is it an upgrade over GPT5 codecs? I'd say from a speed perspective, yes. From a pers perspective, potentially I need to do more tests comparing it to GPT5 codecs. I'll probably do a follow-up video that compares the two as well where I'll give it a test between the two and we'll find out. Make sure to sub and turn on notifications for that. But overall, I am really, really impressed with Claude Code with Sonnet 45. It is much cheaper because you don't have to use Opus anymore, which was significantly more expensive than Sonnet. You can use the cheaper model. You can get better performance and you can get significantly better speed. I hope you built this out with me so you have a cool application your own to use. I hope you learned something as well. Sonnet 45 I'd say is a big success, but we got announcements from Google coming up in the next week. We got announcements from OpenAI coming up in the next week for their dev day. So stick around for that. That's going to be massive as well. But at for at the moment, I am probably going to be using Claude Code. Hope this video was helpful. Leave a like if it was and I'll see you in the next