Bug: ZenStack v2 loses type information in TypeScript types for delegated polymorphic models

[ellie-xpawn]

Description and expected behavior
There is a mismatch between the TypeScript type generated for the base model and all of its delegated submodels.

Consider the following schema:

model Base {
  id String @id @default(cuid(2))
  type String
  @@delegate(type)
}

model Foo extends Base {
  foo Number
}

model Bar extends Base {
  bar String
}

The types generated are as follows:

type Base = {
  id: string
  type: "Foo"
  foo: number
} | {
  id: string
  type: "Bar"
  bar: string
}

type Foo = {
  id: string
  type: string // Expected: "Foo"
  foo: number
}

type Bar = {
  id: string
  type: string // Expected: "Bar"
  bar: string
}

The types of the submodels Foo and Bar lose their discriminator, while the Base union does not. As a workaround, I use the following pattern everywhere:

type Foo = Extract<Base, { type: "Foo" }>
type Bar = Extract<Base, { type: "Bar" }>

Environment (please complete the following information):

• ZenStack version: 2.21.0
• Prisma version: 6.18.0
• Database type: PostgreSQL

Additional context