`addUsersToAlbum` fails if any user is already a member

[timonrieger]

I have searched the existing issues, both open and closed, to make sure this is not a duplicate report.

• Yes

The bug

If you call addUsersToAlbum with multiple users and one of them is already a member of the album, the entire request fails rather than adding the remaining users.

Expected: Skip already-existing members, add the rest, return partial results or a clear per-user status.

Actual: Request fails with an error for the duplicate user; no users are added.

The OS that Immich Server is running on

Version of Immich Server

v2.7.5

Version of Immich Mobile App

Platform with the issue

• Server
• Web
• Mobile

Device make and model

No response

Your docker-compose.yml content

na

Your .env content

na

Reproduction steps

1. Add a single user (Bob) to an album so he becomes a member:
   PUT /api/albums/{albumId}/users {"albumUsers":[{"userId":"<bob-id>","role":"viewer"}]}
2. In one request, add Bob (already a member) and Alice (not yet a member):
   PUT /api/albums/{albumId}/users {"albumUsers":[{"userId":"<bob-id>","role":"viewer"},{"userId":"<alice-id>","role":"viewer"}]}
   => Returns 400 Bad Request: {"message":"User already added"}
3. Check the album's member list — Alice was not added.

Relevant log output

Additional information

No response