Problem

When a struct is reached via *T, generateSchemaRefFor sets schema.Nullable = true to encode nullability of that one reference site:

isNullable := false
for t.Kind() == reflect.Ptr {
    t = t.Elem()
    isNullable = !isRoot
}
// ...
schema.Nullable = isNullable

With ExportComponentSchemas: true, that same *openapi3.Schema body later becomes the canonical component definition shared by every \$ref site:

g.componentSchemaRefs[typeName] = struct{}{}
return openapi3.NewSchemaRef(fmt.Sprintf("#/components/schemas/%s", typeName), schema), nil

So the nullable flag leaks into the component itself. Real-world example from a Fuego-based API:

components:
  schemas:
    Channel:
      type: object
      nullable: true   # <-- wrong, the component is always defined
      properties: { ... }
    AddChannelRequest:
      properties:
        channel:
          \$ref: '#/components/schemas/Channel'  # this single use was *Channel

Codegen tools (Orval, openapi-typescript) interpret nullable on a component body as "the type itself can be null" and emit broken TypeScript:

export interface Channel {
  // ...
} | null   // <-- syntax error

Fix

Clear schema.Nullable right before registering the schema as a component. Nullability of the body is meaningless once the body is shared by every reference site; the field-level decision belongs at the \$ref site (and OpenAPI 3.0 has no clean way to mark a \$ref as nullable, but that's a separate concern). Inline schemas (the fallback at the bottom of the function) keep the existing nullable behavior.

Test

TestExportComponentSchemasNoNullableOnBody registers Wrapper{ Data *Channel }, exports components, and asserts schemas["Channel"].Value.Nullable == false.

The existing ExampleThrowErrorOnCycle snapshot is unaffected (it doesn't enable ExportComponentSchemas).