Description
The problem
In the last few days the Modern Forms integration is returning the following error:
Failed setup, will retry: Invalid response from API: (431, {'message': 'Header fields are too long for server to interpret'})
With debug logging enabled the only relevant entries for Modern Forms are:
2025-06-12 13:12:40.464 DEBUG (MainThread) [homeassistant.components.modern_forms.coordinator] Finished fetching modern_forms data in 0.118 seconds (success: False)
What version of Home Assistant Core has the issue?
2025.6.0
What was the last working version of Home Assistant Core?
No response
What type of installation are you running?
Home Assistant OS
Integration causing the issue
Modern Forms
Link to integration documentation on our website
https://www.home-assistant.io/integrations/modern_forms/
Diagnostics information
No option for diagnostic data other than the provided log message above.
Example YAML snippet
Anything in the logs that might be useful for us?
Failed setup, will retry: Invalid response from API: (431, {'message': 'Header fields are too long for server to interpret'})
Additional information
No response