The legacy Agentforce Builder is implementing an on/off switch to change the reasoning engine to GPT-5.6 Luna on October 15, 2026.
Changing the reasoning engine requires weeks of testing to ensure continued functionality and expected behavior. To avoid extra testing in the future, we recommend upgrading to the new Agentforce Builder to unlock enhanced features, ensure long-term support, and avoid extra testing for the model switch. To learn more, Upgrade an Agent from the Legacy Builder to the New Builder.
If you don't want to upgrade to the new builder, you must change the legacy builder reasoning engine to GPT-5.6 Luna and test extensively:
- From the App Launcher, enter
agentforce agents, and then select Agentforce Agents. - Click the name of the agent you want to change, then click the edit icon next to Description.
- At the end of the agent description, add the following text:
#agent_new_gpt_model:on#. If this text is not in the description, the agent will continue to use GPT-4o. - Click Save.
- Test your agent in Preview, then on a sandbox org, then move the change to production when you're ready.
Where: This change applies to Lightning Experience in Enterprise, Performance, and Unlimited editions with Foundations or Agentforce 1 editions.
When: Change is available on a rolling basis in Salesforce orgs upgraded to Winter ’27 starting the week of October 12, 2026.
Why: This change is in preparation for OpenAI GPT-4o’s deprecation in Spring 2027. After that, all legacy builder reasoning engines will be automatically changed to GPT-5.6 Luna. Test now to avoid distruptions.