If you’ve ever built a web application using Streamlit, you’ve probably encountered a few quirks along the way. Recently, I stumbled upon a frustrating issue with my Streamlit app’s MFA login process. After submitting the OTP, my app mysteriously skipped critical code execution steps—breaking the login workflow entirely. Let’s break down exactly what went wrong, and how we’ve been troubleshooting.
How My Streamlit App’s MFA Login Typically Works
When building web apps, user authentication is critical. Multi-Factor Authentication (MFA) adds a crucial extra step to secure user accounts. The login flow for my app using Streamlit is straightforward at first glance:
- User enters their username and password.
- If MFA is enabled, the app generates a QR code that users scan with their authenticator app (such as Google Authenticator).
- Users then enter the One-Time Password (OTP) that their authenticator generates.
- The app validates the OTP, logs the user in, and lets them access content.
Sounds simple enough, right? Well, not exactly.
What Exactly Went Wrong?
Everything usually worked perfectly before. But suddenly, after entering the correct OTP, the Streamlit app started skipping executing essential parts of the login code entirely.
Specifically, the app showed and accepted input via the OTP form correctly. But right after submission, it looked like the code wasn’t progressing as expected. The page refreshed—but user authentication steps didn’t complete. No session state validation, no successful login messages, nothing happened afterward.
At first, I suspected the issue might have been due to my EnableMFA variable or some broken conditional logic in my code.
Steps Taken to Troubleshoot the Problem
Naturally, the first thought in troubleshooting such an issue is to review conditional variables, since logic skips often happen due to conditions evaluating incorrectly.
First, I double-checked my EnableMFA variable to ensure it correctly enabled the multi-factor functionality. But the variable was correctly set, ruling that out.
Next, I reviewed all conditional statements, such as if/else blocks controlling the OTP verification code. For good measure, I even printed debug statements at different points to trace exactly where the code stopped executing.
Despite all these checks, the form submission process still mysteriously refused to move past OTP acceptance. It simply refreshed and skipped critical statements after submitting the OTP.
Digging Deeper into Code Analysis
Streamlit’s session state can often be tricky—it controls the behavior and statefulness of Streamlit apps. Maybe the issue was rooted deeper in session state management?
My Streamlit MFA activation code looked something like this:
import streamlit as st
import pyotp
if 'authenticated' not in st.session_state:
st.session_state.authenticated = False
def activate_mfa():
totp_secret = pyotp.random_base32()
st.session_state['totp_secret'] = totp_secret
otp_uri = pyotp.totp.TOTP(totp_secret).provisioning_uri(name="user@email.com")
st.write("Scan this QR code with your authenticator app:")
st.image(generate_qr_code(otp_uri))
if st.button("Enable MFA"):
activate_mfa()
otp_code = st.text_input("Enter your OTP", type='password')
if otp_code:
totp = pyotp.TOTP(st.session_state.get('totp_secret'))
if totp.verify(otp_code):
st.session_state.authenticated = True
st.success("Login successful")
else:
st.error("OTP incorrect")
This snippet involves generating a TOTP secret, displaying a QR code, and verifying user OTP input against this secret. Initially, this worked fine—but now it’s failing silently after submission.
Turns out, the code’s logic itself wasn’t the problem. Rather, the form submission and immediate Streamlit page refresh were causing issues with Streamlit’s session state. Basically, the issue was with how Streamlit handles interactions within form submissions.
Handling Errors Properly—Rollback and Exception Management
It’s very important to handle exceptions effectively, especially in authentication scenarios. If something goes wrong with OTP validation, your app must handle it gracefully.
During troubleshooting, I wrapped OTP verification into a try-except block:
try:
totp = pyotp.TOTP(st.session_state['totp_secret'])
if totp.verify(otp_code):
st.session_state.authenticated = True
st.success("Login successful!")
else:
st.error("Wrong OTP, try again!")
except Exception as e:
st.error(f"An error occurred: {str(e)}")
st.session_state.authenticated = False
Adding this code snippet significantly improved error visibility. With explicit error handling, I quickly realized Streamlit hadn’t actually failed silently—it instead kept resetting the state under certain conditions.
The Streamlit User Experience After OTP Submission
The primary complaint here is how this issue affects a normal user’s workflow:
- Upon entering a correct OTP, users expect seamless login.
- Instead, they were facing confusing screen refreshes and no visible logins or error messaging initially.
- Clicking the “Login” or “Enable MFA” button multiple times led to frustration as it appeared non-responsive.
Improving error handling (as shown above) helps the user clearly know what’s happening behind the scenes. However, there still remained difficulty because upon submission, Session State data and verification state were not persisting properly.
In other words, users ended up stuck in a repetitive OTP submission loop every single time, damaging their experience significantly.
What’s Causing This and How Can We Resolve It?
After considerable debugging, the root cause seems closely tied to how Streamlit manages form data and the script rerun lifecycle. Every form submission triggers a rerun which, unless managed properly, wipes specific elements of the session state.
A helpful troubleshooting tip here is to consult the official Streamlit Session State documentation or look closely at similar issues on Stack Overflow.
To persist OTP verification and avoid losing state after submission, explicitly initializing session state elements helps:
if 'totp_secret' not in st.session_state:
st.session_state['totp_secret'] = pyotp.random_base32()
if 'authenticated' not in st.session_state:
st.session_state.authenticated = False
Explicitly managing session state variables from the start ensures their correct values after script reruns—and after form submissions in Streamlit. Careful session management often remedies problems involving skipped code execution.
Still Need More Help?
Even experienced Streamlit developers sometimes hit roadblocks. I’ve documented this issue with detailed screenshots and a screen recording to help illustrate the problem clearly—take a look at the video in the appendix below.
I’d love your thoughts—have you faced similar Streamlit form submission or MFA problems in your apps, and how did you resolve them? Feel free to leave a comment or suggestion below; collaboration on tricky problems often leads to quicker solutions!
Appendix: Screen Recording for Reference
Here’s a quick screen recording demonstrating this exact OTP submission issue with my Streamlit app—pay close attention to the code execution skips after OTP entry.
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