Unable to set Azure OpenAI Assistant to work with gpt-4.1-mini even though it's deployed and available

Question

I have a correctly deployment model GPT-4.1-mini in Azure Open AI which is shown up as an option in the Assistants Playground of AI Foundry. When I'm trying to set the Assistant to use this deployment (which has a deployment status of Completed) I am getting this error:

Deployment not found**: Selected deployment may be in progress or deleted. Please try again in a few minutes or select another deployment.**

The deployment is correct, I can use it elsewhere such as for chat completion, just failing when I try to set it for an Assistant.

Answer 1

Hello David Captur,

Welcome to the Microsoft Q&A and thank you for posting your questions here.

I understand that you are unable to set Azure OpenAI Assistant to work with gpt-4.1-mini even though it's deployed and available.

The error occurs because Azure OpenAI’s Assistants API restricts compatibility to specific models. While GPT-4.1-mini is functional for standard chat completions, it lacks official support for Assistants as of April 2025. This discrepancy triggers a misleading “Deployment not found” error, despite the model being deployed correctly. The issue stems from backend validation rejecting unauthorized models, even if they appear in the AI Foundry Playground UI due to synchronization delays or bugs. - https://learn.microsoft.com/en-us/azure/ai-services/openai/whats-new and https://learn.microsoft.com/en-us/azure/ai-services/openai/concepts/model-retirements

To resolve this, replace the unsupported GPT-4.1-mini deployment with a compatible model such as GPT-4 Turbo (gpt-4-turbo), GPT-4 (gpt-4), or GPT-3.5-Turbo (gpt-3.5-turbo). Redeploy one of these models via the Azure portal, then update your Assistant configuration to reference the new deployment. This ensures compatibility with Assistants’ advanced features like persistent threads and tool integrations. Or you continue with somewhere else it works as you stated.

I hope this is helpful! Do not hesitate to let me know if you have any other questions or clarifications.

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