Update local-dev.mdx

  Main Changes:

  1. Added "Required Configuration" section - Shows the complete wrangler.json structure needed for local
  development
  2. Clarified required fields:
    - name field in container config
    - instance_type field (typically "standard")
    - nodejs_compat compatibility flag
  3. Added troubleshooting note - Explains that missing these fields causes "Connection refused" errors
  4. Removed misleading phrase - Changed "without additional configuration" to just describing how to run the
  commands

  The updated documentation now accurately reflects what's actually needed to get containers working locally,
  preventing the issues we encountered. This should help other developers avoid the debugging session we just
  went through!

Author: zach-is-my-name

src/content/docs/containers/local-dev.mdx

@@ -5,11 +5,32 @@ sidebar:
   order: 3
 ---
 
-You can run both your container and your Worker locally, without additional configuration, by running [`npx wrangler dev`](/workers/wrangler/commands/#dev) (or `vite dev` for Vite projects using the [Cloudflare Vite plugin](/workers/vite-plugin/)) in your project's directory.
+You can run both your container and your Worker locally by running [`npx wrangler dev`](/workers/wrangler/commands/#dev) (or `vite dev` for Vite projects using the [Cloudflare Vite plugin](/workers/vite-plugin/)) in your project's directory.
 
 To develop Container-enabled Workers locally, you will need to first ensure that a
 Docker compatible CLI tool and Engine are installed. For instance, you could use [Docker Desktop](https://docs.docker.com/desktop/) or [Colima](https://github.com/abiosoft/colima).
 
+## Required Configuration
+
+For local development, your `wrangler.json` or `wrangler.jsonc` file must include specific configuration fields:
+
+```json
+{
+  "containers": [{
+    "name": "your-container-name",      // Required for local development
+    "class_name": "YourContainerClass", // Your Durable Object class name
+    "image": "./path/to/Dockerfile",    // Path to your Dockerfile
+    "instance_type": "standard",        // Required for proper runtime behavior
+    "max_instances": 2                  // Optional, not enforced locally
+  }],
+  "compatibility_flags": ["nodejs_compat"] // Required when using Container class from @cloudflare/containers
+}
+```
+
+:::note
+The `name` and `instance_type` fields are essential for local development. Without them, you may encounter "Connection refused: container port not found" errors even if your container is properly configured.
+:::
+
 When you start a dev session, your container image will be built or downloaded. If your
 [Wrangler configuration](/workers/wrangler/configuration/#containers) sets
 the `image` attribute to a local path, the image will be built using the local Dockerfile.
@@ -46,6 +67,15 @@ you are using in your container code.
 
 ## Troubleshooting
 
+### Container Configuration Errors
+
+If you encounter "Connection refused: container port not found" errors during local development, verify that:
+
+1. Your container configuration includes a `name` field
+2. Your container configuration includes an `instance_type` field (typically `"standard"`)
+3. You have `nodejs_compat` in your `compatibility_flags` array if using the Container class from `@cloudflare/containers`
+4. Your Dockerfile includes the necessary `EXPOSE` instructions (see below)
+
 ### Exposing Ports
 
 In production, all of your container's ports will be accessible by your Worker, so you do not need to specifically expose ports using the [`EXPOSE` instruction](https://docs.docker.com/reference/dockerfile/#expose) in your Dockerfile.