# 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: 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: ``` GET https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0224.md?ask= ``` The question should be specific, self-contained, and written in natural language. 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.