---
title: AionUI
description: Set up Half Off Dev in AionUI as an OpenAI-compatible provider, in one click or by hand, and chat with Claude, GPT and Gemini at half price.
---

AionUI is an open-source desktop app that puts a graphical interface on top of AI models. It accepts Half Off Dev as an OpenAI-compatible provider, so a single key brings Claude, GPT and Gemini into it at half their official prices. Create an [API key](/app/keys) first.

## Import in one click {#import}

From [API keys](/app/keys), open **Use in tools** → **AionUI** and click **Open in AionUI**. AionUI must be installed; it receives the provider with your key. A brand-new key is filled in already. For an older one, paste the whole key into the dialog, since Half Off Dev can't show a stored key again.

## Manual setup {#manual-setup}

Add a provider in AionUI using:

| Field | Value |
| --- | --- |
| Provider type | OpenAI-compatible (or "New API") |
| API host | `https://halfoff.dev` |
| API key | your `ho-...` key |

AionUI adds `/v1` to the host by itself. Once the provider is saved, add model ids, for instance `gemini-3.1-pro`, `claude-sonnet-5.5` or `gpt-6.1-sol`. The [model list](/models) shows all of them.

## Fixing errors {#troubleshooting}

| What you see | What to do |
| --- | --- |
| `401` `Invalid or revoked API key` | The key was mistyped, cut short or revoked. Paste it again or make a new one. |
| `404` `Model '...' is not available` | That id doesn't exist. Copy one from `GET /v1/models` or the [model list](/models). |
| `404` with `/v1/v1/` in the path | The API host ends in `/v1`. Change it to `https://halfoff.dev`. |
| `404` `Unknown endpoint` | AionUI is calling an API Half Off Dev doesn't serve, such as embeddings. Use Half Off Dev for chat and another provider for that feature. |
| `402` | The balance is empty or the key has hit its spend cap. See [Billing](/docs/account/billing). |

Any other status is explained in [Errors](/docs/api/errors).