> 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/5000-to-5008/aur5002.md).

# AUR5002

## Error Message

`AUR5002: invalid config, expecting a function or an object, received {{value}}`

Where `{{value}}` is the type of the invalid parameter passed to the configure method.

## Description

This error occurs when `HttpClient.configure()` is called with a parameter that is neither a function nor a configuration object. The configure method accepts either:

1. A callback function that receives a configuration object
2. A plain configuration object

## Common Scenarios

### Passing Invalid Types

```typescript
import { HttpClient } from '@aurelia/fetch-client';

const client = new HttpClient();

// ❌ Wrong: Passing a string
client.configure('invalid'); // Throws AUR5002

// ❌ Wrong: Passing a number  
client.configure(123); // Throws AUR5002

// ❌ Wrong: Passing null/undefined
client.configure(null); // Throws AUR5002
```

## Solutions

### 1. **Use Configuration Callback (Recommended)**

```typescript
// ✅ Correct: Pass a configuration function
client.configure(config => {
  return config
    .withBaseUrl('https://api.example.com')
    .withDefaults({
      headers: { 'Content-Type': 'application/json' }
    });
});
```

### 2. **Use Configuration Object**

```typescript
// ✅ Correct: Pass a configuration object
const configObject = {
  baseUrl: 'https://api.example.com',
  defaults: {
    headers: { 'Content-Type': 'application/json' }
  }
};

client.configure(configObject);
```

## Debugging Tips

1. **Check Parameter Type**: Ensure you're passing a function or object
2. **Verify Syntax**: Make sure callback syntax is correct
3. **TypeScript**: Use TypeScript to catch type errors at compile time


---

# 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 by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://docs.aurelia.io/developer-guides/error-messages/5000-to-5008/aur5002.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

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.