> For the complete documentation index, see [llms.txt](https://docs.aurelia.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0224.md).

# AUR0224

## Error Message

`AUR0224: Invalid @observable decorator usage, cannot determine property name`

## Description

This error occurs when Aurelia cannot determine the property name for an `@observable` decorator usage. This is usually caused by applying `@observable` in an unsupported way or in an environment that does not provide the required decorator metadata.

## Common Scenarios

* Using `@observable` without proper TypeScript decorator configuration.
* Applying `@observable` to an unsupported target (for example not a class field/property in the expected form).

## Solution

* Ensure your project is configured for decorators as required by Aurelia.
* Apply `@observable` to a class field/property as supported by your build setup.

## Troubleshooting

* Verify your TypeScript/bundler configuration for decorators.
* Check that the decorator is applied to a class field and not a local variable or unsupported construct.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0224.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.