First Check

• I added a very descriptive title here.
• I used the GitHub search to find a similar question and didn't find it.
• I searched the FastAPI documentation, with the integrated search.
• I already searched in Google "How to X in FastAPI" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to FastAPI but to Pydantic.
• I already checked if it is not related to FastAPI but to Swagger UI.
• I already checked if it is not related to FastAPI but to ReDoc.

Commit to Help

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Example Code

from enum import Enum
from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

class StatusEnum(str, Enum):
    ACTIVE = "active"
    INACTIVE = "inactive"
    PENDING = "pending"

class User(BaseModel):
    name: str
    status: StatusEnum

@app.get("/user", response_model=User)
def get_user():
    return {"name": "Alice", "status": "ACTIVE"}

Description

When generating the OpenAPI schema, the enum StatusEnum in the User model shows incorrect values: it displays ["ACTIVE", "INACTIVE", "PENDING"] instead of the expected lowercase ["active", "inactive", "pending"].

I expected the OpenAPI documentation to match the Enum string values exactly as defined.

The response from the endpoint works correctly ("status": "ACTIVE"), but the docs show inconsistent casing.

Operating System

Windows

Operating System Details

No response

FastAPI Version

FastAPI Version: 0.121.3

Pydantic Version

Pydantic Version: 2.11.1

Python Version

Python Version: 3.11.11

Additional Context

I suspect this has to do with FastAPI or Pydantic's internal conversion of Enum names for OpenAPI generation, but I couldn’t find a way to preserve the original Enum values in the docs.