After starting a Unity AI subscription, AI Gateway connection may fail with an error stating the plan lacks AI gateway sessions. This occurs because a Unity AI seat has not been assigned to the user. MCP connections remain free and unaffected. To resolve, log into cloud.unity.com, navigate to Subscriptions, select the Unity AI subscription, assign a seat to your account, then fully restart the Editor before reconnecting. The seat requirement applies only to AI Gateway, not MCP.
Symptoms
After starting a Unity AI subscription, the AI Gateway connection fails with the following message:
- AI Gateway error message
- Your Unity plan does not include AI gateway sessions. Upgrade your Unity plan to add more.
MCP connections are free for all users with no concurrency limits. If you previously saw a plan/capacity-limit error for MCP, it no longer applies.
Cause
This is most likely because you have not assigned a Unity AI seat to yourself. This applies to AI Gateway only — MCP does not require a seat and is unaffected by plan or licensing status.
Resolution
Assign a Unity AI Seat
- Log in to cloud.unity.com with your Unity credentials
- Go to Subscriptions
- Click your Unity AI subscription
- Click Assign Seats
- Assign the seat to your account
- Close the Editor completely, then relaunch it before attempting the AI Gateway connection again
If connecting via the new Unity CLI, MCP Mode uses the same free, unlimited MCP connection — the seat/plan requirement above applies only to AI Gateway.