Microsoft Copilot Studio - End of support for the GPT-5.5 Chat model

Beginning October 31, 2026, the GPT-5.5 Chat model will reach end of support in Microsoft Copilot Studio and will no longer be available for selection as a model option. Additionally, on October 31, 2026, agents still configured to use the GPT-5.5 Chat model will be automatically migrated.

How does this affect me?
Beginning October 31, 2026, agents using the GPT-5.5 Chat model will automatically be migrated to a supported replacement model. Agents using the standard harness will move to GPT Chat Latest. Agents using the GitHub Copilot harness will move to the latest Luna model.

You may switch your agent to a different supported model before or after the migration date. The option to continue using the GPT-5.5 Chat model or extend its availability is not available.

What action do I need to take?
Please identify agents currently using the GPT-5.5 Chat model, test them with the appropriate replacement model, and review prompts, configurations, and integrations for compatibility. Make any necessary updates and select the replacement model from the model picker before the migration date. If your agent is still configured to use the GPT-5.5 Chat model on October 31, 2026, it will fall back to a different available model, as mentioned above.

Learn more

• Test your agent
• Select a primary AI model for your agent
• Manage the AI model lifecycle for Copilot Studio agents