> ## Documentation Index
> Fetch the complete documentation index at: https://developer.plugchoice.com/llms.txt
> Use this file to discover all available pages before exploring further.

# unknown-version

> The Plugchoice-Version header names a version the SDK API doesn't know.

| Status | Title |
| - | - |
| `400` | Unknown API version |

## Where you see it

**Your server**, on any SDK API endpoint.

## What it means

The `Plugchoice-Version` request header is set, but not to a version the SDK API speaks.

`detail` lists the versions it does.

## What to do

* Send one of the versions in `detail`; today that is `2026-10-07`.
* Or leave the header out to get the newest version. Pinning is better: see [Versions](/sdk/versioning).

## Example

```json theme={null}
{
  "type": "https://developer.plugchoice.com/sdk/errors/unknown-version",
  "title": "Unknown API version",
  "status": 400,
  "code": "unknown-version",
  "detail": "Plugchoice-Version must be one of: 2026-10-07."
}
```


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