When using Cursor’s Plan Mode, we explicitly selected GPT-5.6 as the model. However, when moving from Plan to Build/Implementation, Cursor automatically switched to Claude Sonnet 4.6, even though we did not select this model.
This is unexpected and creates both quality and token-consumption issues.
Steps to Reproduce
Open a project in Cursor Editor.
Switch to Plan Mode.
Select GPT-5.6 as the model.
Create a plan and allow Cursor to complete the planning process.
Proceed from Plan Mode to Build/Implementation.
Observe the model being used for the Build process
Expected Behavior
If the user explicitly selects GPT-5.6, Cursor should preserve that model selection when moving from Plan Mode to Build Mode, unless:
the user explicitly changes the model, or
Cursor cannot use the selected model, in which case it should clearly notify the user and ask for confirmation before switching.
A model that has been disabled/hidden by the user should never be automatically selected for execution.
Could someone please respond? This is consuming my Claude Sonnet tokens, which I don’t want to use at all. It keeps happening repeatedly, and the default model switches to Sonnet as soon as I click Build. Please look into this urgently and make sure my selected model remains unchanged instead of automatically switching to Sonnet.
Plan mode has a separate “model used to build this plan” picker that’s independent of the model you choose while planning. When it isn’t set to follow your chat model, Build runs on that picker’s model (it defaults to Sonnet 4.6) and sticks there for future plans, which is why Build keeps switching off GPT-5.6.
To fix it: open the plan (View Plan), click the model selector next to the Build button, and choose “Inherit Agent Model” (or pick GPT-5.6 there directly). Build will then follow your chat model.
You’re right that a model you’ve hidden shouldn’t get auto-selected here. That’s not intended behavior, and it’s an issue we’re tracking. I’ll post an update in this thread when I have one.
Hi Mohit , Thanks for your response. However I have selected the GPT-5.6 in the build plan , but as soon as clicks on the build , it gets changed to sonnet . so manually I need to stop the build plan and explicitly given a text prompt that build with GPT 5.6 sol only and again select GPT 5.6 Sol which is not expected behavior
The inline “Created Plan” card in chat has no model picker, so clicking Build there uses the stored build model (Sonnet). Open the plan with View Plan, click the picker right next to the Build button, and choose “Inherit Agent Model” rather than just picking GPT-5.6. Inherit ties Build to your chat model persistently, whereas a one-off pick there can still get overridden. If it still flips to Sonnet after you set Inherit from View Plan, that’s not intended and it’s an issue we’re tracking, so tell me and share the request ID from that build and I’ll dig in.
