`gr.State` + MCP is broken

[apolinario]

Describe the bug

gr.State breaks MCP parameter mapping

Repro: https://huggingface.co/spaces/multimodalart/mcp-breaking-state

Code:

import gradio as gr
 
def process(name: str, hidden_state: str, flag: bool, gallery_images: list = []):
"""
Process inputs and return a result.
 
Args:
name: A text input from user
hidden_state: A value from gr.State (hidden from MCP)
flag: A boolean checkbox
gallery_images: Gallery images list
 
Returns:
str: Result showing all received values
"""
return f"name={name}, hidden_state={hidden_state}, flag={flag}, gallery={gallery_images}"
 
 
with gr.Blocks() as demo:
gr.Markdown("# Gradio MCP Bug: gr.State breaks parameter order")
 
name_input = gr.Textbox(label="Name", value="test")
hidden_state = gr.State(value="hidden_value")
flag_input = gr.Checkbox(label="Flag", value=True)
gallery = gr.Gallery(label="Images", value=[])
 
output = gr.Textbox(label="Result")
 
btn = gr.Button("Process")
btn.click(
process,
inputs=[name_input, hidden_state, flag_input, gallery],
outputs=[output],
api_visibility="public",
)
 
 
if __name__ == "__main__":
demo.launch(mcp_server=True, show_error=True)

MCP schema shows 3 params (State is hidden):

• name: string
• flag: boolean
• gallery_images: array

Function expects 4 params:

• name: str
• hidden_state: str ← gr.State
• flag: bool
• gallery_images: list

When calling MCP with {"name": "hello", "flag": true, "gallery_images": []}:

Parameter	Expected	Actual
name	"hello"	"hello" ✓
hidden_state	"hidden_value"	"hidden_value" ✓
flag	true	[] (gallery value) ✗
gallery_images	[]	True (flag value) ✗

Error:
1 validation error for GalleryData
Input should be a valid list [type=list_type, input_value=True, input_type=bool]

The State default seems injected, but all parameters after the State are shifted by one position.

Have you searched existing issues? 🔎

• I have searched and found no existing issues

System Info

gradio==6.0.1

Severity

I can work around it