URGENT HELP: Azure AD (Microsoft) Login Fails on Streamlit Cloud

Community Cloud
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Summary: Microsoft Entra ID (Azure AD) authentication fails immediately upon clicking the login button on Streamlit Cloud (v1.52.0).

The Core Issue:

  • Localhost: :white_check_mark: WORKING (Login proceeds and succeeds).

  • Streamlit Cloud: :cross_mark: FAILS immediately when the login button is clicked.

  • Error: The app crashes before sending the request to the Azure authentication server.

  • Code/Config: No configuration changes were made. The issue appeared suddenly this week.

Specific Error Message: 400: 'NoneType' object does not support item assignment (A Python error indicating a critical configuration variable is missing or None).

Technical Details:

  • Streamlit Version: 1.52.0

  • Python Version: 3.13

  • App Type: Web App (Confidential Client, uses Client Secret).

  • Goal: User authentication via Microsoft.

Key Questions for the Community:

  1. Since Localhost works, is it possible that a recent change in Streamlit Cloud (v1.52.0) has broken how essential secrets (e.g., Client ID, Client Secret) are loaded from secrets.toml during the initial login request phase?

  2. What environment checks should I perform to debug why critical configuration variables are being read as None only on the Cloud?

Thank you!