Better Auth omits unknown user columns from responses unless declared in user.additionalFields

Adding a column to the user table by hand does not make it appear in the session or user object. The library serializes only the fields it knows about, so the value is in the database and invisible to the application.

Declare extra fields under user.additionalFields with a type, and re-run the schema generator. The important option there is input. Left at its permissive default, the field is accepted from the client sign-up payload, so a column named plan or role becomes user-settable at registration. Set input: false on every field that grants privileges or represents billing state, and audit existing declarations for the same problem, because the failure is silent and only visible by inspecting rows created by real users.