The first example we'll work on is an end-to-end RAG chatbot. Let's use Claude Code to explore the code base. Before we start using Claude Code to write lots of code for us, let's talk about how we can use this tool to get up to speed on larger code bases. Right here, I have an application where I can chat with Claude about course materials from Deep Learning AI. So let's try asking an outline of a course. For example, what is the outline of the MCP Build Rich-Context AI Apps with Anthropic. We'll see here that I'll get a response with quite a bit of detail around the lessons and descriptions for each of those lessons. With that in mind, let's see how we can get up to speed on the underlying code that powers this application. Back in VS Code, I have the terminal open here and I'm going to hop into Claude Code just by typing in claude and pressing enter. In this application, I can start chatting with my codebase. So I'm going to start with a high-level question just to give me an overview of the codebase. What we're going to see Claude Code do is agentically search over the codebase, figure out some of the most important files and give me a description of what's happening in this application. Instead of searching through each individual file, we're going to agentically search and find the most relevant ones. So here we're going to get some information about the architecture, the key components, some of the features, and now if there are particular things I want to dig into, I can easily do that. I can also ask other higher level questions like how are these documents processed? In this application, we're using Retrieval Augmented Generation to fetch information about these courses. If I want to get more information about that process, I can ask a question like this one. We like to say that Claude Code is a fantastic engineer alongside you, but it's an even better explainer. So as you're getting up to speed with new codebases, new data sets. First, start using Claude Code as a way to explain things to you, so that when you ask it to write code, you can have a better understanding of what's going on. Here we can see the sources in the code base that are actually splitting text into chunks, that are adding lesson context and that are storing course metadata. This ability to quickly get up to speed with a code base, especially when you might not be familiar with the underlying technology or language, is exceptionally valuable. Instead of navigating to each of these folders and figuring out what's going on, we can ask more specific questions and even get diagrams and visualizations made for us. So the first thing I'll ask Claude is to trace the process of handling a user's query from front end to back end. You can imagine you might have some limited knowledge in one of the parts of the stack or you're not familiar with how this is all happening. So Claude Code is going to give us quite some useful information here. What's useful when you're seeing Claude Code work is its ability to give you a bit of a to-do list, so you can start to understand what's happening. At any point in time, you can press escape and guide Claude Code to follow a different set of to-dos, but in this case, I feel pretty good about what it's doing. It's going to start tracing from the frontend, start following API endpoints, analyze our Retrieval Augmented Generation system, and then figure out how to actually generate the response. It's reading the appropriate files that are handling these particular tasks and finishing up its list to give us a powerful summary. As we're in this environment, we can stay within VS Code or open up Claude Code in its own dedicated terminal instance. That's completely up to you as you're working in this application. Once it's done, we can see a very detailed path for what's happening here. Not only can I read each of these step-by-step, I can even ask Claude to write this to a file, but I'm seeing in quite a bit of detail what's happening on the front end with some JavaScript, what happens once that reaches my back end, what the Retrieval Augmented Generation system is doing, how I'm generating a response. Finally, how I'm searching through my vector database, how I'm filtering what's necessary, getting a response back, and then finally, sending that to the user. There's a lot that's going on in this application. And I can use Claude to dive deeper into any of those pieces. But let's just say I learn best from visualizations. So let's ask Claude to draw a diagram that illustrates this flow. We can ask Claude to draw diagrams for web visualizations. We can ask for ASCII art. But let's see what Claude comes up with with its own intelligence and knowledge of how the application works. So let's see what Claude code has come up with. We've got a really nice diagram here showing us the step-by-step process. So it can't create these visual diagrams. We could always ask it to use some something like D3.js or recharts if we want something like a web application. But we can see right here, we've got a really nice diagram. From the front end, making a request to the back end, calling the necessary functions, generating the response necessary if there's any history involved, talking directly to the large language model with our system prompts and our tools and a query, figuring out where to go next, searching through our vector database using Chroma DB, getting back results formatting that, sending it to the model to produce a final response. There's quite a bit of detail that goes into this. And if we want, we can even augment Claude with additional tools for generating the visualizations that we want. But out of the box, just getting this information quickly and efficiently is going to help us get up to speed with this codebase in a fraction of time that we used to spend. So with that in mind, let's ask a very simple question, how do I run this application? You might be in a situation where there's a new technology here, a new idea. Very simply, it's nice to just know how to get up and running. I can see here, my API documentation, my web interface, and if there are any environment variables I need, I'm good to go. Now that you've gotten an idea of how to just start talking to Claude Code. Let's talk a little bit about some of the more powerful features with Claude Code. When you start working with an application in Claude Code, one of the first things we recommend you do is run a command called /init. You can see here in Claude Code, when I add this slash, we have a list of many built-in commands that I can use. /init allows me to initialize a CLAUDE.md file with the codebase documentation. The CLAUDE.md file is mission critical for introducing memory for Claude Code, so that it knows how best to work in your codebase. The CLAUDE.md file is very useful for specifying how you want things to be run. This could be your tests, this could be your linting, and any long-term memory that you want Claude to have each time you're working with Claude Code for this particular project. Instead of making this from scratch, /init is going to analyze the codebase to figure out at a high level what it should know about each time you're working with this application. There are three different CLAUDE.md files that you can make, like the one generated with /init all the way here on the left. This CLAUDE.md file lives in your application. You can have many of them in nested sub folders. But this is shared with other engineers and committed to your version control. Another option is if you have personal instructions and customizations, think specific for your editing environment and terminal environment, you can put that in a CLAUDE.local.md file. This is git ignored and not shared with other engineers. Finally, in your home directory, in the .claude folder, you can add a CLAUDE.md and you can think of this like a global claude.md for all projects on your machine. This is helpful if you want Claude to follow instructions across a wide range of projects that you build with Claude Code. We can go ahead and allow Claude Code to find different files so that it knows how best to create this CLAUDE.md file. This CLAUDE.md file is meant to be added to your current git project and shared with other team members. As more individuals work on the codebase, they can add to this CLAUDE.md file, and you can even nest CLAUDE.md files in subdirectories if you need more specific instructions for things like the backend or frontend or our docs that we have here. What's really nice about using a tool like Claude Code with Visual Studio Code, is that as I see changes to files, I can see those visually in my editor. And anytime that I am using a tool in Claude Code, it's going to ask me for permissions. This mission critical human in the loop is really important when you get up and running, and if you don't need Claude to ask you every single time, can always use this second option. We'll go ahead and auto accept those edits and we'll see that a CLAUDE.md file has been created for us. To give you a quick walk through, we can see it's given us a project overview, key technologies, an architectural overview, a nice little diagram here, some core components. and much more. If we want things to change to this particular CLAUDE.md, we can easily do so. As it continues searching the codebase, it makes additional edits here to my CLAUDE.md and gives me a summary of what's been done. When I'm using a tool like Claude Code in VS Code, I have the ability to specify which file I'm in and even get information about particular lines. To set this up, I'm going to use the /ide command. and I can see right here that I'm connected with Visual Studio Code. Now that I'm in Visual Studio Code, we can see right here that the second that I visit a file, it's tagged right here for what's going on. This gives Claude Code the right context for which file I'm in and if there are questions I have about that file, it makes it easier for Claude Code to identify that. If I ever want to make any changes to my CLAUDE.md file, I can manually write that if I'd like. Or I can use a handy command to go ahead and use this pound key and directly add to memory. So I'm just going to say here, always use UV. to run the server, do not use pip directly. This is a package manager in the Python ecosystem and I want to make sure that Claude doesn't get confused. When I use this shortcut, we can see there are different places where this memory can be saved. We mentioned there is the Project memory that is included in git for everyone on your team to use. We have local memory that is gitignored but just useful for you as the developer. and then User memory that is applicable to all projects you use with Claude Code. For this one, I'll just go ahead and update the project memory. I can see here, I've made that change. And if I look in my CLAUDE.md, I'll see right here, I have some mentions to using UV to make sure that I'm doing that correctly. If I want to be more specific, I can also say, make sure to use UV to manage all dependencies. I'll add this to my CLAUDE.md and we'll see right here that it's been added. If I take a quick look at this particular file, we can see any mention of dependencies now includes UV. We spoke a little bit about some of the commands that are built into Claude Code like /emit. There are a couple other useful ones that I want to showcase here. And in fact, we're going to see later on in this course, we can even make our own. One of the first ones I want to walk you through is /help. This shows me right off the bat a quick description of all the commands. and a quick summary. This is useful as you're getting up to speed with Claude code. The next one I want to showcase is a command called /clear. What this allows you to do is clear the conversation history and start from scratch. This is very helpful as you shift gears and build new features. This allows you to clear the context window and start fresh. If you want to continue the conversation, have a smaller context window, but still have a summary of what's been done, we also have this command /compact that allows you to clear the history, but keep a summary so that you can build off with Claude having an idea of what was done before. One more useful command is the escape key that allows you to get out of whatever command you're in. So if I'm going and trying to do something like /compact and I want to stop that process, I can always press escape. If I start a process with Claude Code to explain what is in the codebase. If I want to stop that process, escape will allow me to interrupt and continue, onwards. So don't feel like you have to wait for Claude Code if you're not getting what you need. In the next lesson, we'll start using Claude Code to build features, add to files, modify changes, and make sure we're doing the right thing along the way. Before we hop off, one last useful piece with Claude Code is its ability to work with Git. So I've made some small changes to this application, and I want to add and commit these changes. Instead of me manually have to write the Git commands, write a descriptive commit message, going to actually have Claude Code do that work for us. And what's really nice is Claude Code's ability to add and commit the necessary commands. I'll go ahead and add this particular file, not only commit, but you can see here, I've got this really nice descriptive commit message. That's incredibly useful as we start asking Claude Code about historical changes with git. and when we push this to GitHub and other people are reading the changes we made. So we'll add and commit and the next lesson, we'll use Claude Code to start writing lots of things for us.