Desktop GPT Automation Connector

I need a cross-platform desktop application (Windows and macOS) that feels just like ChatGPT yet goes a step further: every conversation should be able to trigger one of my custom GPT models and immediately pipe the result into another application... (Budget: $250 - $750 USD, Jobs: Agile Development, API Development, Continuous Integration, Database Management, Desktop Application, RESTful API, Software Documentation, Software Engineering)