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fix: add SCHEDULE-AGENT=CLIENT to prevent CalDAV duplicate invitations #26970

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fix: add SCHEDULE-AGENT=CLIENT to prevent CalDAV duplicate invitations #26970

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@yuvrajangadsingh yuvrajangadsingh commented Jan 18, 2026

Summary

Fixes #9485

Adds SCHEDULE-AGENT=CLIENT parameter to ATTENDEE lines in CalDAV createEvent and updateEvent operations.

Per RFC 6638 Section 7.1, this tells the CalDAV server that the client handles scheduling, preventing servers like Fastmail, NextCloud, and others from sending their own duplicate invitation emails.

What changed

  • Added addScheduleAgentClient() helper function that adds ;SCHEDULE-AGENT=CLIENT to ATTENDEE lines
  • Applied to both createEvent and updateEvent in CalendarService.ts
  • Skips lines that already have SCHEDULE-AGENT parameter

Test plan

  • Create a CalDAV calendar event with attendees - verify no duplicate emails
  • Update a CalDAV calendar event - verify no duplicate emails
  • Verify existing SCHEDULE-AGENT parameters are not duplicated

@yuvrajangadsingh
fix: add SCHEDULE-AGENT=CLIENT to prevent CalDAV duplicate invitations
18152d7 
Fixes calcom#9485

Adds SCHEDULE-AGENT=CLIENT parameter to ATTENDEE lines in CalDAV
createEvent and updateEvent operations. Per RFC 6638 Section 7.1,
this tells the CalDAV server that the client handles scheduling,
preventing servers like Fastmail and NextCloud from sending their
own duplicate invitation emails.
@github-actions github-actions bot added $500 caldav area: caldav, fastmail, Baïkal, Kerio, mailbox, nextcloud Low priority Created by Linear-GitHub Sync 🐛 bug Something isn't working 💎 Bounty A bounty on Algora.io labels Jan 18, 2026
@graphite-app graphite-app bot added the community Created by Linear-GitHub Sync label Jan 18, 2026
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yuvrajangadsingh commented Jan 18, 2026

/claim #9485

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No issues found across 1 file

@yuvrajangadsingh yuvrajangadsingh mentioned this pull request Jan 18, 2026
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💎 Bounty A bounty on Algora.io 🐛 bug Something isn't working caldav area: caldav, fastmail, Baïkal, Kerio, mailbox, nextcloud community Created by Linear-GitHub Sync Low priority Created by Linear-GitHub Sync size/S $500

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CalDAV integration with Fastmail is generating duplicate, erroneous invitation emails.

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