RootPath not properly working from Gradio version 4.21.0 and onward (including 5.16.0) when using gr.mount and FastAPI directly

[jayteaftw]

Describe the bug

root_path is not properly working when mounting gradio application to fastapi as theme.css becomes unaccessible. Looks like how the theme file is being accessed changed from 4.20.1 to 4.21.0. Interestingly, when deployed and used with localhost, it works an intended on gradio on 5.16.0, only when deployed on a https webserver its not able to find the theme.css. However neither the 4.20.1, 4.21.0 or 5.16.0 work properly as they all show 404 connection loss when actually submitting a job. With gradio==5.16.0 and no FastAPI mount the program works as intended but I need to mount it using FastAPI to get use external authentication which is absolutely neccessary.

Have you searched existing issues? 🔎

• I have searched and found no existing issues

Reproduction

import gradio as gr
from fastapi import FastAPI

demo = gr.Interface(
    fn=greet,
    inputs=["text", "slider"],
    outputs=["text"],
)

ROOT_PATH = '/chat/tech-library'
app = FastAPI(root_path = ROOT_PATH)
app = gr.mount_gradio_app(app, demo, path="/app")

uvicorn --host "0.0.0.0"  --proxy-headers --port 7860 serve:app

Screenshot

Gradio==4.21.0 to gradio==5.16.0

Gradio==4.20.1

gradio==5.16.0 w/ Localhost

gradio==5.16.0 w/o FastAPI
ENV GRADIO_SERVER_NAME="0.0.0.0"
GRADIO_ROOT_PATH="/chat/tech-library"

import gradio as gr
from fastapi import FastAPI

demo = gr.Interface(
    fn=greet,
    inputs=["text", "slider"],
    outputs=["text"],
)
demo.launch()

gradio==5.16.0 w/ FastAPI but w/o RootPath

Logs

System Info

Gradio Environment Information:
------------------------------
Operating System: Linux
gradio version: 5.16.0
gradio_client version: 1.7.0

------------------------------------------------
gradio dependencies in your environment:

aiofiles: 23.2.1
anyio: 4.8.0
audioop-lts is not installed.
fastapi: 0.115.8
ffmpy: 0.5.0
gradio-client==1.7.0 is not installed.
httpx: 0.28.1
huggingface-hub: 0.28.1
jinja2: 3.1.5
markupsafe: 2.1.5
numpy: 1.26.4
orjson: 3.10.15
packaging: 24.2
pandas: 2.2.3
pillow: 11.1.0
pydantic: 2.10.6
pydub: 0.25.1
python-multipart: 0.0.20
pyyaml: 6.0.2
ruff: 0.9.6
safehttpx: 0.1.6
semantic-version: 2.10.0
starlette: 0.45.3
tomlkit: 0.13.2
typer: 0.15.1
typing-extensions: 4.12.2
urllib3: 2.3.0
uvicorn: 0.34.0
authlib; extra == 'oauth' is not installed.
itsdangerous; extra == 'oauth' is not installed.


gradio_client dependencies in your environment:

fsspec: 2024.9.0
httpx: 0.28.1
huggingface-hub: 0.28.1
packaging: 24.2
typing-extensions: 4.12.2
websockets: 14.2

Severity

Blocking usage of gradio