docs: document build output + Cloud troubleshooting (#13774)

www/apps/book/public/llms-full.txt

@@ -4,7 +4,7 @@
 
 In this chapter, you'll learn how to create a production build of your Medusa application for deployment to a hosting provider.
 
-Next chapters explain how to deploy the Medusa application.
+The next chapter explains how to deploy your Medusa application.
 
 The below instructions are useful for self-hosting your Medusa application. You can also use [Cloud](https://docs.medusajs.com/cloud/index.html.md) to deploy and manage your Medusa application without worrying about infrastructure. Medusa will handle the configurations, deployment, and scaling for you.
 
@@ -21,24 +21,7 @@ So, to create the production build, run the following command in the root of you
 npx medusa build
 ```
 
-***
-
-## Build Output
-
-The `build` command creates a `.medusa` directory in the root of your project that contains your build assets. Do not commit this directory to your repository.
-
-The `.medusa` directory contains the following subdirectories:
-
-- `.medusa/server`: Contains the production build of your Medusa application.
-- `.medusa/server/public/admin`: Contains the production build of the admin dashboard.
-
-### Separate Admin Build
-
-The `build` command accepts a `--admin-only` option that outputs the admin to the `.medusa/admin` directory. This is useful when deploying the admin dashboard separately, such as on Vercel:
-
-```bash
-npx medusa build --admin-only
-```
+The command will create a `.medusa/server` directory in the root of your project that contains your build assets. The next sections explain how to use the build output.
 
 ***
 
@@ -46,7 +29,7 @@ npx medusa build --admin-only
 
 To start the Medusa application after running the `build` command:
 
-You need to run these steps every time you run the `build` command, as the `.medusa` directory is recreated each time.
+You need to run these steps every time you run the `build` command, since the `.medusa/server` directory is recreated each time.
 
 1. Change to the `.medusa/server` directory and install the dependencies:
 
@@ -60,7 +43,7 @@ cd .medusa/server && npm install
 cp ../../.env .env.production
 ```
 
-When `NODE_ENV=production`, the Medusa application loads the environment variables from `.env.production`. Learn more about environment variables in [this guide](https://docs.medusajs.com/learn/fundamentals/environment-variables/index.html.md).
+When `NODE_ENV=production`, the Medusa application loads the environment variables from `.env.production`. Learn more in the [environment variables guide](https://docs.medusajs.com/learn/fundamentals/environment-variables/index.html.md).
 
 3. Set `NODE_ENV` to `production` in the system environment variable:
 
@@ -76,9 +59,9 @@ npm run start
 
 ### Authentication Locally in Production Build
 
-When the Medusa application is started in production (`NODE_ENV=production`) or staging modes, cookie settings are more strict. You can only use cookie authentication if the client application is served from the same domain as the Medusa server, and the domain is not `localhost` or part of the [public suffix list](https://publicsuffix.org/).
+When the Medusa application is started in production (`NODE_ENV=production`) or staging mode, cookie settings are stricter. Cookie authentication only works if the client application is served from the same domain as the Medusa server, and the domain is not `localhost` or part of the [public suffix list](https://publicsuffix.org/).
 
-So, if you try to access the Medusa Admin locally in production mode, you won't be able to log in.
+So if you try to access the Medusa Admin locally in production mode, you won't be able to log in.
 
 To access the Medusa Admin locally in production mode, set the `projectConfig.cookieOptions` in your `medusa-config.ts` file to be less strict. For example:
 
@@ -96,12 +79,61 @@ module.exports = defineConfig({
 
 In this example, you set `sameSite` to `lax` and `secure` to `false`, which allows cookies to be sent over non-secure connections and from different domains.
 
-Then, rebuild the Medusa application and start it again, as described in the [steps above](#start-built-medusa-application). You can now access the Medusa Admin locally in production mode.
+Then rebuild the Medusa application and start it again as described in the [steps above](#start-built-medusa-application). You can now access the Medusa Admin locally in production mode.
 
 Make sure to remove the `projectConfig.cookieOptions` configuration once you're done testing locally, as it's not secure for production environments.
 
 ***
 
+## Build Output
+
+The `build` command creates a `.medusa/server` directory in the root of your project that contains your build assets. Do not commit this directory to your repository. This directory should be generated as part of your deployment process.
+
+The `.medusa/server` directory contains the following:
+
+![.medusa/server directory structure](https://res.cloudinary.com/dza7lstvk/image/upload/v1760709518/Medusa%20Book/output-dir_dlklk6.jpg)
+
+- `public/admin`: Contains the production build of the admin dashboard. The `public` directory is publicly accessible.
+- `src`: Contains the compiled JavaScript files of your `src` directory.
+- `instrumentation.js`: The compiled [instrumentation configuration file](https://docs.medusajs.com/learn/debugging-and-testing/instrumentation/index.html.md), if you have one.
+- `medusa-config.js`: The compiled Medusa configuration file.
+- `package.json` and a lock file: The dependencies required to run the Medusa application in production.
+
+### Built Assets
+
+The `build` command compiles and copies `.{ts,js,tsx,jsx}` files in your project, such as those in the root directory and in the `src` directory.
+
+If you have other assets, such as JSON files or fonts, that you need in your Medusa backend at runtime, you need to copy them to the `.medusa/server` directory as part of your build process.
+
+For example, consider you have a `src/data` directory that contains JSON files needed at runtime. You can add a `postbuild` script to your `package.json` file to copy this directory after the build process:
+
+```json title="package.json"
+{
+  "scripts": {
+    "postbuild": "cp -r src/data .medusa/server/src/data",
+    "build": "medusa build && npm run postbuild"
+  }
+}
+```
+
+This script copies the `src/data` directory to the `.medusa/server` directory after the build process.
+
+Do not expose sensitive files in your deployments, especially in the `.medusa/server/public` directory, as they will be publicly accessible. Sensitive files include those containing API keys, database credentials, or any other confidential information.
+
+### Customize Admin Build
+
+The admin dashboard is built with [Vite](!https://vitejs.dev/). If you need to customize the build process to include additional static assets, you can modify the Vite configuration with the [admin.vite](https://docs.medusajs.com/learn/configurations/medusa-config/index.html.md) option in your `medusa-config.ts` file.
+
+### Separate Admin Build
+
+The `build` command accepts a `--admin-only` option that outputs the admin to the `.medusa/admin` directory. This is useful when deploying the admin dashboard separately, such as on Vercel:
+
+```bash
+npx medusa build --admin-only
+```
+
+***
+
 ## Deploying Production Build
 
 The next chapter covers how to deploy the production build.