# AUR0821

## Error Message

`AUR0821: Invalid command "{{command}}" usage with [repeat.for] option "contextual". Only "bind" or static assignment is supported.`

Where `{{command}}` is the binding command used on the `repeat.for` binding.

## Description

This error occurs when using `repeat.for="...; contextual"` together with an unsupported binding command. With `contextual`, Aurelia only supports `bind` (two-way) or static assignment for the contextual bindings.

## Example Trigger

```html
<!-- ❌ Unsupported command with contextual -->
<div repeat.for="item of items; contextual: true; key.trigger: item.id">
  ${item.name}
</div>
```

## Correct Usage

Use `bind` (or static assignment) for contextual bindings.

```html
<!-- ✅ bind is supported -->
<div repeat.for="item of items; contextual: true; key.bind: item.id">
  ${item.name}
</div>
```

## Troubleshooting

* Check the binding command in the error (`{{command}}`) and change it to `.bind` (or remove the command for static assignment).
* If you need event/listener behavior, move it to an element inside the repeater rather than the `repeat.for` declaration.