[event UI] Some atendees not loading on dropdown list

Steps to reproduce

1. Create/edit an event
2. Type the email of a contact in the attendees list
3. On the http request (developer mode) data is returned for the contact, but not shown on the dropdown list

Happens on some contacts and internal users, some others are shown while typing, others only when there is an exact match with the email, others not showing anything until full email is introduced but the contact is not recognized.

Sometimes, even when full email is introduced or when doing copy-paste, cannot add the attendee because the list is empty. Seems a problem with regex, when there is a full match that does not show in the dropdown on partial match, the contact will not show. For example:

• There is a contact xavier@whatever.net
• Introduce xavier@what --> does not show anything on the list
• Introduce xavier@whatever.ne --> the list show xavier@whatever.ne (because it considers a valid email but not on contacts list)
• Introduce xavier@whatever.net --> does not show anything on the list

Very annoying because the contacts that does not work on the dropdown cannot be added to the event, even by typing the correct email for the contact.

See pictures with different cases.

Expected behavior

While typing on the text box, the whole list of matching attendees (email and/or name of the contact) returned by server should be shown on the dropdown list.

Actual behavior

The contacts are returned on the http query result but the info is not shown on the dropdown list

Calendar app version

5.5.5

CalDAV-clients used

Thunderbird, DAVx5

Browser

140.0.7339.214 (Compilació oficial) (arm64)

Client operating system

OSX M2, 2022, 15.6.1 (24G90)

Server operating system

Docker nextcloud:latest inside Debian GNU/Linux 12 (bookworm)

Web server

Nginx

Database engine version

PostgreSQL

PHP engine version

PHP 8.4

Nextcloud version

30.0.0.14

Updated from an older installed version or fresh install

None

List of activated apps

Enabled:
  - activity: 3.0.0
  - announcementcenter: 7.2.1
  - appointments: 2.4.6
  - audioplayer: 3.5.1
  - bruteforcesettings: 3.0.0
  - calendar: 5.5.5
  - circles: 30.0.0-dev
  - cloud_federation_api: 1.13.0
  - comments: 1.20.1
  - contacts: 7.3.2
  - contactsinteraction: 1.11.0
  - dav: 1.31.1
  - deck: 1.14.6
  - drawio: 3.0.9
  - encryption: 2.18.0
  - external: 5.5.2
  - federatedfilesharing: 1.20.0
  - federation: 1.20.0
  - files: 2.2.0
  - files_bpm: 1.7.1
  - files_downloadlimit: 3.0.0
  - files_pdfviewer: 3.0.0
  - files_reminders: 1.3.0
  - files_sharing: 1.22.0
  - files_trashbin: 1.20.1
  - files_versions: 1.23.0
  - firstrunwizard: 3.0.0
  - forms: 5.2.1
  - groupfolders: 18.1.7
  - impersonate: 1.17.1
  - integration_dropbox: 4.0.3
  - integration_google: 4.1.0
  - integration_notion: 1.3.1
  - logreader: 3.0.0
  - lookup_server_connector: 1.18.0
  - music: 2.3.0
  - nextcloud_announcements: 2.0.0
  - notes: 4.12.3
  - notifications: 3.0.0
  - oauth2: 1.18.1
  - onlyoffice: 9.11.0
  - password_policy: 2.0.0
  - passwords: 2025.10.10
  - photos: 3.0.2
  - polls: 8.3.10
  - privacy: 2.0.0
  - provisioning_api: 1.20.0
  - quota_warning: 1.21.0
  - recommendations: 3.0.0
  - related_resources: 1.5.0
  - riotchat: 0.19.0
  - secrets: 2.1.4
  - serverinfo: 2.0.0
  - settings: 1.13.0
  - sharebymail: 1.20.0
  - snappymail: 2.38.2
  - socialsharing_telegram: 3.3.0
  - spreed: 20.1.10
  - support: 2.0.0
  - survey_client: 2.0.0
  - suspicious_login: 8.0.0
  - systemtags: 1.20.0
  - tasks: 0.16.1
  - tasmota_control: 0.0.1
  - text: 4.1.0
  - theming: 2.5.0
  - theming_customcss: 1.18.0
  - twofactor_backupcodes: 1.19.0
  - twofactor_totp: 12.0.0-dev
  - updatenotification: 1.20.0
  - user_ldap: 1.21.0
  - user_status: 1.10.0
  - viewer: 3.0.0
  - webhook_listeners: 1.1.0-dev
  - workflow_script: 1.15.0
  - workflowengine: 2.12.0

Nextcloud configuration

{
    "system": {
        "htaccess.RewriteBase": "\/",
        "memcache.local": "\\OC\\Memcache\\APCu",
        "apps_paths": [
            {
                "path": "\/var\/www\/html\/apps",
                "url": "\/apps",
                "writable": false
            },
            {
                "path": "\/var\/www\/html\/custom_apps",
                "url": "\/custom_apps",
                "writable": true
            }
        ],
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "localhost",
            "192.168.1.52",
            "raspberrypi.local",
            "cloud.mydomain.com"
        ],
        "trusted_proxies": "***REMOVED SENSITIVE VALUE***",
        "forwarded_for_headers": [
            "HTTP_X_FORWARDED_FOR",
            "HTTP_X_FORWARDED",
            "HTTP_X_CLUSTER_CLIENT_IP"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "pgsql",
        "version": "30.0.0.14",
        "overwrite.cli.url": "https:\/\/cloud.mydomain.com",
        "overwritehost": "cloud.mydomain.com",
        "overwriteprotocol": "https",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "app_install_overwrite": [
            "documentserver_community",
            "whiteboard",
            "pdfdraw"
        ],
        "mail_sendmailmode": "smtp",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpmode": "smtp",
        "mail_smtpauth": 1,
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "587",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpauthtype": "PLAIN",
        "default_phone_region": "ES",
        "wopi_allowlist": "83.XXXXX",
        "opcache.memory_consumption": "1024",
        "maintenance": false,
        "twofactor_enforced": "true",
        "twofactor_enforced_groups": [],
        "twofactor_enforced_excluded_groups": [],
        "theme": "",
        "loglevel": 0,
        "skeletondirectory": "",
        "templatedirectory": "",
        "maintenance_window_start": 1,
        "ldapProviderFactory": "OCA\\User_LDAP\\LDAPProviderFactory",
        "debug": false
    }
}

Web server error log

No errors detected

Log file

Browser log

No console logs

Additional info

Partial match not working:

---

Query for partial match with results from server:

---

Partial match working only for some external users (some external users not showing, internal users not showing):

---

Query returning results working:

---

Partial match not working:

---

Exact match working:

---

Partial match working:

---

Email is correct but list is empty:

Start by reproducing the issue in the event attendee dropdown while watching the HTTP request and its returned contacts. Compare cases that appear with cases that remain hidden, including partial and exact email matches. Done means every matching attendee returned by the server is shown and can be added to the event.