app.py

import gradio as gr

def respond(newVal, previous_val):
    if previous_val is None:
        previous_val = newVal
    return previous_val

with gr.Blocks() as demo:
    val = gr.State(None)
    input_text = gr.Textbox(label="Input")
    output_text = gr.Textbox(label="Output")

    input_text.change(respond, [input_text, val], val)
    val.change(lambda val: val, val, output_text)

demo.launch()