BUG: Stale widgets from previous page runs are not removed when a spinner is later invoked

[connortann]

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

In certain circumstances, UI elements from previous page executions unexpectedly remain on the screen.

This is possibly related to #14249 , which was apparently caused by a recent change #13849 and fixed by #14251. However, this bug occurs in a slightly context, without use of tabs or cached functions, so I think it's a distinct issue.

I've boiled down a minimal reproducible example below. The bug seems to occur if a call to st.spinner is made after a selection widget, and the precise behaviour varies depending on whether Expander containers are used and whether other objects are rendered before the spinner.

I noticed two slight variants of this bug, depending on whether some markdown is rendered before the call to st.spinner. In each cases a different stale widget is left:

Variant 1: without markdown call

As per the code example below: the "Button 1" widget (and Expander box) remains visible, but the "Button 2" widget is cleared.

bug_spinner_A.webm

Variant 2: with markdown call

As above but uncommenting the call to st.markdown: now the "Button 1" widget is indeed cleaned up properly, but the "Button 2" widget is now erroneously left.

bug_spinner_B.webm

Reproducible Code Example

import streamlit as st

st.write("Streamlit version:", st.__version__)

choice = st.radio("Radio", options=["A", "B"])
if choice == "B":
    with st.expander("Inner", expanded=True):
        st.button("Button 1")
    st.button("Button 2")

# Uncommenting this line changes the behaviour of the bug:
# st.markdown("Some text")

with st.spinner():
    pass

Steps To Reproduce

1. Click "B"
2. Click "A"

Expected Behavior

When "A" is selected, the Expander and Button widgets should be hidden.

Current Behavior

When "A" is selected, the Expander box and "Button 1" Button remain visible.

Is this a regression?

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

Debug info

• Streamlit version: 1.55.0
• Python version: 3.10
• Operating System: Linux
• Browser: Chrome

Additional Information

No response

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[connortann]

Update: I tested with the streamlit-nightly issue, version 1.55.1.dev20260316, and the bug no longer occurs. So, I think this has been fixed by #14251. Thanks, streamlit team!

Perhaps this issue should be closed, and/or perhaps the reproducible example might be helpful as a test case to prevent a future regression.

[mayagbarnes]

Hi @connortann, thanks for submitting this issue!
As you noted above I ran it on latest develop and do not see the bug anymore. Will go ahead and close this but please feel free to open another if you encounter another variation of the issue.
The fix will be in the next release (around 3/31)!