Remote calendar crashes the system

[luca-angemi]

The problem

Adding a remote calendar URL from Outlook crashes the system (RPi4).

In a couple of retries it manages to add the calendar after 30+ seconds.

2025-04-01 14:08:42.066 WARNING (MainThread) [homeassistant.helpers.entity] Updating state for calendar.work (<class 'homeassistant.components.remote_calendar.calendar.RemoteCalendarEntity'>) took 35.159 seconds. Please create a bug report at https://github.com/home-assistant/core/issues?q=is%3Aopen+is%3Aissue+label%3A%22integration%3A+remote_calendar%22

although, when I try to get the events from a calendar view the system crashes again.

What version of Home Assistant Core has the issue?

2025.4.0b10

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

remote_calendar

Link to integration documentation on our website

https://rc.home-assistant.io/integrations/remote_calendar

Diagnostics information

No response

Example YAML snippet

Anything in the logs that might be useful for us?

Additional information

No response

[home-assistant]

Hey there @Thomas55555, mind taking a look at this issue as it has been labeled with an integration (remote_calendar) you are listed as a code owner for? Thanks!

Code owner commands

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• @home-assistant unassign remote_calendar Removes the current integration label and assignees on the issue, add the integration domain after the command.
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[Thomas55555]

Is it a huge calendar?
I saw a PR for another calendar integration, which limited the loaded event, because of performance issues. Sounds similar.

[luca-angemi]

I can't judge if it's huge.

There are less than 30 events and the ics file is 58 Kb for approx 1200 lines.

I created an empty calendar and tried that. It was imported in less than 1 second so, yes, it seems to be related to events.

[neilmartin83]

I am observing this behaviour as well. My ICS file from Outlook is 240kb and 5145 lines when downloaded directly.

If I subscribe to the same Outlook ICS URL using a Google Account, then share the ICS link for it from Google Calendar, I can add that to Home Assistant as a Remote Calendar. It's a bit convoluted but a workaround nonetheless. :-)

[fanuch]

I have this too.

My O365 calendar is probably large.
The following events crash my HA:

• Adding Remote Calendar
• Navigating to Calendar dashboard
• Adding calendar widget

I'm going to try and get more debug information but just wanted to make sure the issue was catalogued

[luca-angemi]

I am observing this behaviour as well. My ICS file from Outlook is 240kb and 5145 lines when downloaded directly.

If I subscribe to the same Outlook ICS URL using a Google Account, then share the ICS link for it from Google Calendar, I can add that to Home Assistant as a Remote Calendar. It's a bit convoluted but a workaround nonetheless. :-)

Nice workaround. I imported the outlook calendar into google and since I was using the Google Calendar integration I just reloaded it and it pop up smoothly. Thanks!

[snozzlebert]

Same here. Complete crash of Home Assistant (2025.4.0) when adding a Outlook ICS url as remote calendar.
68 events, 1700 lines, 57 Kb.

[mattenz]

Same issue is happening for me with 2025.4.1 and an O365/Exchange Online calendar. The ICS file is 206 lines at 6KB

[LeiChat]

Experienced the same issue today with a basic free Outlook account calendar. The ICS file 46KB with 60 events.

[picki72]

Same issue my end. Several timeouts also in other integrations when this integration was enabled. After switching it off the other stuff returned to normal operations.

[akorb90]

Can reproduce this issue with a pretty big Outlook.com calendar.

[luca-angemi]

Tested the fix.
Now adding the integration is fine (the same calendar was added in a couple of seconds) but viewing the events in the frontend (or clicking on the entity to see the more info dialog) still crashes the system.