Checklist

• I have searched the existing issues for similar issues.
• I added a very descriptive title to this issue.
• I have provided sufficient information below to help reproduce this issue.

Summary

After entering multiple lines of text into the st.chat_input control, the input box remains at the multi-line height even after sending the message

or clearing the input. It does not shrink back to the original single-line height.

Reproducible Code Example

import streamlit as st
text =  st.chat_input("input")
if text:
    st.write(text)

Steps To Reproduce

Use Streamlit version 1.47.1.
Add st.chat_input to your app, for example:

import streamlit as st
text = st.chat_input("input")
if text:
st.write(text)

Run the app.
In the chat input, enter text that spans multiple lines (e.g., using Shift+Enter).
Send the message (press Enter or click send).
Observe the chat input box.

Expected Behavior

After sending the message, the chat input box should shrink back to its original single-line height if the input area is empty.

Current Behavior

The chat input box remains at the expanded multi-line height, even after sending the message or clearing the input.

Is this a regression?

• Yes, this used to work in a previous version.

Debug info

• Streamlit version: 1.47.1
• Python version: 3.11.8
• Operating System: Ubuntu 22 LTS
• Browser: Edge

Additional Information

No response