# TEN add-on system (/en/ai/ten-agent/architecture/addon-system)

> For AI agents: see the complete documentation index at [llms.txt](/llms.txt).

The TEN Framework uses **add-ons** as its basic software modules. Add-ons are self-contained components that implement specific functionality within the TEN Framework. All features and capabilities in a TEN application are built using these modular add-ons.

The TEN Framework supports the following types of add-ons:

* **TEN extension** - Implements core application logic and features
* **TEN extension group** - Groups multiple extensions for coordinated functionality
* **TEN protocol** - Handles communication protocols and data exchange

## Loading add-ons [#loading-add-ons]

To load an add-on into the TEN runtime, you need:

1. **Add-on name**

   The name must be globally unique within your TEN application. If you load multiple add-ons with the same name, the TEN runtime exhibits undefined behavior and may fail to load the second add-on properly.

2. **Add-on folder location**

   Specify the directory path where the TEN runtime can find the add-on's files. The runtime uses this directory as the `base_dir` to load configuration files such as `manifest.json` and `property.json`.

   The add-on registration API attempts to detect this directory automatically. If automatic detection fails, you must explicitly specify the `base_dir` path.

3. **Add-on instance**

## Registering add-ons [#registering-add-ons]

You can register add-ons using one of the following methods:

1. **Use the explicit registration API**

   Call the registration API to manually register the add-on's `base_dir` with the TEN runtime.

   <CalloutContainer type="info">
     <CalloutDescription>
       Currently, only the standalone testing framework provides this API.
     </CalloutDescription>
   </CalloutContainer>

2. **Use the designated directory structure**

   Place your add-ons in the `ten_packages/` directory of your TEN application. The application automatically discovers and loads add-ons at startup when you organize them as follows:

   ```text
   .
   └── ten_packages/
       ├── extension/
       │   ├── <extension_foo>/
       │   └── <extension_bar>/
       ├── extension_group/
       │   └── <extension_group_x>/
       └── protocol/
           └── <protocol_a>/
   ```