[Python] FastAPI Swagger UI shows alias instead of original field name in response schema

I have the following FastAPI code using Pydantic:

from fastapi import FastAPI
from fastapi.routing import APIRouter
from pydantic import BaseModel, Field
from typing import Optional

app = FastAPI()
router = APIRouter()

class UserSchema(BaseModel):
user_name: Optional[str] = Field(None, alias="name")

class Config:
populate_by_name = True

@router.get(
"/user",
tags=["user"],
summary="Get user",
response_model=UserSchema,
response_model_by_alias = False
)
async def get_user():
user_data = {"name": "John Doe"}
return UserSchema(**user_data).model_dump()

Current Behavior


API Response: (Correct)

{
"user_name": "John Doe"
}


Swagger UI Response Schema: (Incorrect — it shows the alias instead of the original field name) Image

{
"name": "string"
}

Expected Behavior


I want the Swagger UI (OpenAPI) response schema to show the field name user_name instead of the alias name.

What I've Tried

1. Using by_alias=False when serializing the response.

async def get_user():
user_data = {"name": "John Doe"}
return UserSchema(**user_data).model_dump(by_alias=False)

1. Adding populate_by_name = True in the Pydantic model's Config.

class UserSchema(BaseModel):
user_name: Optional[str] = Field(None, alias="name")

class Config:
populate_by_name = True

1. Setting response_model_by_alias = False in the route

@router.get(
"/user",
tags=["user"],
summary="Get user",
response_model=UserSchema,
response_model_by_alias = False
)


How can I configure FastAPI to make the Swagger UI display the field name (user_name) instead of the alias (name)?

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