[Bug]: Several different federation features fail

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

Several federation features are not usable, including

• Calendar shares
• federated conversations in Talk

However, federated file shares do work.

Server A runs on Ubuntu 24.04.3 with Nginx 24.0 and php-fpm 8.3, using local PostgreSQL and Redis.
Server B runs in 32-apache Docker image, installed on other Ubuntu 24.04.3, using PostgreSQL and Redis installed in containers.

Steps to reproduce

1. Create two Nextcloud servers
2. Install Talk or Calendar on both servers
3. Try to share calendar with user from other server or try to add user from other server to conversation

Expected behavior

• Users from two servers can talk with each other in chat
• Calendar is shared between servers as read-only

Nextcloud Server version

32

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.3

Web server

Nginx

Database engine version

PostgreSQL

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

### Server A: ###
{
    "system": {
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "###",
            "###"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "pgsql",
        "version": "32.0.1.2",
        "overwrite.cli.url": "https:\/\/###",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "maintenance_window_start": 1,
        "memcache.local": "\\OC\\Memcache\\APCu",
        "memcache.distributed": "\\OC\\Memcache\\Redis",
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "port": 6379
        },
        "default_phone_region": "RU",
        "skeletondirectory": "",
        "maintenance": false,
        "forbidden_filename_basenames": [
            "con",
            "prn",
            "aux",
            "nul",
            "com0",
            "com1",
            "com2",
            "com3",
            "com4",
            "com5",
            "com6",
            "com7",
            "com8",
            "com9",
            "com\u00b9",
            "com\u00b2",
            "com\u00b3",
            "lpt0",
            "lpt1",
            "lpt2",
            "lpt3",
            "lpt4",
            "lpt5",
            "lpt6",
            "lpt7",
            "lpt8",
            "lpt9",
            "lpt\u00b9",
            "lpt\u00b2",
            "lpt\u00b3"
        ],
        "forbidden_filename_characters": [
            "<",
            ">",
            ":",
            "\"",
            "|",
            "?",
            "*",
            "\\",
            "\/"
        ],
        "forbidden_filename_extensions": [
            " ",
            ".",
            ".filepart",
            ".part"
        ],
        "defaultapp": "files",
        "theme": "",
        "loglevel": 2,
        "user_oidc": {
            "login_label": "{name}"
        },
        "trusted_proxies": "***REMOVED SENSITIVE VALUE***",
        "app_install_overwrite": [
            "cadviewer"
        ],
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpmode": "smtp",
        "mail_sendmailmode": "smtp",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpauth": true,
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "465",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpsecure": "ssl"
    }
}

### Server B: ###
{
    "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
            }
        ],
        "memcache.distributed": "\\OC\\Memcache\\Redis",
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "password": "***REMOVED SENSITIVE VALUE***",
            "port": 6379
        },
        "overwriteprotocol": "https",
        "overwrite.cli.url": "https:\/\/###\/nc",
        "overwritewebroot": "\/nc",
        "trusted_proxies": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpmode": "smtp",
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "587",
        "mail_smtpauth": true,
        "mail_smtpauthtype": "LOGIN",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "upgrade.disable-web": true,
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "localhost",
            "###",
            "###"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "pgsql",
        "version": "32.0.3.2",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbtableprefix": "oc_",
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "maintenance_window_start": 23,
        "default_phone_region": "RU",
        "onlyoffice": {
            "editors_check_interval": 0
        },
        "enabledPreviewProviders": [
            "OC\\Preview\\TXT",
            "OC\\Preview\\MarkDown",
            "OC\\Preview\\Imaginary"
        ],
        "preview_imaginary_url": "***REMOVED SENSITIVE VALUE***",
        "user_oidc": {
            "login_label": "###"
        },
        "maintenance": false,
        "mail_sendmailmode": "smtp",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpsecure": "tls",
        "config_preset": 8,
        "forbidden_filename_basenames": [
            "con",
            "prn",
            "aux",
            "nul",
            "com0",
            "com1",
            "com2",
            "com3",
            "com4",
            "com5",
            "com6",
            "com7",
            "com8",
            "com9",
            "com\u00b9",
            "com\u00b2",
            "com\u00b3",
            "lpt0",
            "lpt1",
            "lpt2",
            "lpt3",
            "lpt4",
            "lpt5",
            "lpt6",
            "lpt7",
            "lpt8",
            "lpt9",
            "lpt\u00b9",
            "lpt\u00b2",
            "lpt\u00b3"
        ],
        "forbidden_filename_characters": [
            "<",
            ">",
            ":",
            "\"",
            "|",
            "?",
            "*",
            "\\",
            "\/"
        ],
        "forbidden_filename_extensions": [
            " ",
            ".",
            ".filepart",
            ".part"
        ]
    }
}

List of activated Apps

### Server A: ###
Enabled:
  - activity: 5.0.0-dev.0
  - bruteforcesettings: 5.0.0-dev.0
  - calendar: 6.1.2
  - circles: 32.0.0
  - cloud_federation_api: 1.16.0
  - comments: 1.22.0
  - contacts: 8.1.2
  - contactsinteraction: 1.13.1
  - dav: 1.34.2
  - deck: 1.16.3
  - external: 7.0.0
  - federatedfilesharing: 1.22.0
  - federation: 1.22.0
  - files: 2.4.0
  - files_downloadlimit: 5.0.0-dev.0
  - files_external: 1.24.0
  - files_reminders: 1.5.0
  - files_sharing: 1.24.0
  - files_trashbin: 1.22.0
  - files_versions: 1.25.0
  - forms: 5.2.3
  - groupfolders: 20.1.6
  - imageconverter: 2.1.0
  - logreader: 5.0.0-dev.0
  - lookup_server_connector: 1.20.0
  - nextcloud_announcements: 4.0.0-dev.0
  - notifications: 5.0.0-dev.0
  - notify_push: 1.2.1
  - oauth2: 1.20.0
  - onlyoffice: 9.12.0
  - password_policy: 4.0.0-dev.0
  - passwords: 2025.12.21
  - photos: 5.0.0-dev.1
  - privacy: 4.0.0-dev.0
  - profile: 1.1.0
  - provisioning_api: 1.22.0
  - recommendations: 5.0.0-dev.0
  - related_resources: 3.0.0-dev.0
  - serverinfo: 4.0.0-dev.0
  - settings: 1.15.1
  - sharebymail: 1.22.0
  - side_menu: 5.1.3
  - spreed: 22.0.7
  - support: 4.0.0-dev.0
  - survey_client: 4.0.0-dev.0
  - systemtags: 1.22.0
  - tables: 1.0.2
  - talk_matterbridge: 1.32.1026000
  - tasks: 0.17.1
  - text: 6.0.1
  - theming: 2.7.0
  - twofactor_backupcodes: 1.21.0
  - updatenotification: 1.22.0
  - user_oidc: 8.2.2
  - user_status: 1.12.0
  - viewer: 5.0.0-dev.0
  - weather_status: 1.12.0
  - webhook_listeners: 1.3.0
  - workflowengine: 2.14.0
Disabled:
  - admin_audit: 1.22.0
  - app_api: 32.0.0 (installed 32.0.0)
  - dashboard: 7.12.0 (installed 7.11.0)
  - encryption: 2.20.0
  - files_pdfviewer: 5.0.0-dev.0 (installed 5.0.0-dev.0)
  - firstrunwizard: 5.0.0-dev.0 (installed 4.0.0)
  - mail_roundcube: 1.2.2 (installed 1.2.2)
  - suspicious_login: 10.0.0-dev.0
  - twofactor_nextcloud_notification: 6.0.0-dev.0
  - twofactor_totp: 14.0.0
  - user_ldap: 1.23.0

### Server B: ###
Enabled:
  - activity: 5.0.0-dev.0
  - analytics: 6.0.1
  - bruteforcesettings: 5.0.0-dev.0
  - calendar: 6.1.2
  - circles: 32.0.0
  - cloud_federation_api: 1.16.0
  - comments: 1.22.0
  - contacts: 8.1.2
  - contactsinteraction: 1.13.1
  - dav: 1.34.2
  - deck: 1.16.3
  - external: 7.0.0
  - federatedfilesharing: 1.22.0
  - federation: 1.22.0
  - files: 2.4.0
  - files_antivirus: 6.1.0
  - files_downloadlimit: 5.0.0-dev.0
  - files_fulltextsearch: 32.0.2
  - files_reminders: 1.5.0
  - files_sharing: 1.24.1
  - files_trashbin: 1.22.0
  - files_versions: 1.25.0
  - forms: 5.2.3
  - fulltextsearch: 32.0.0
  - fulltextsearch_elasticsearch: 32.0.1
  - groupfolders: 20.1.6
  - guests: 4.6.0
  - logreader: 5.0.0-dev.0
  - lookup_server_connector: 1.20.0
  - nextcloud_announcements: 4.0.0-dev.0
  - notifications: 5.0.0-dev.0
  - notify_push: 1.2.1
  - oauth2: 1.20.0
  - onlyoffice: 9.12.0
  - password_policy: 4.0.0-dev.0
  - photos: 5.0.0-dev.1
  - previewgenerator: 5.11.0
  - privacy: 4.0.0-dev.0
  - profile: 1.1.0
  - provisioning_api: 1.22.0
  - recommendations: 5.0.0-dev.0
  - related_resources: 3.0.0-dev.0
  - serverinfo: 4.0.0-dev.0
  - settings: 1.15.1
  - sharebymail: 1.22.0
  - side_menu: 5.1.3
  - spreed: 22.0.7
  - support: 4.0.0-dev.0
  - systemtags: 1.22.0
  - tables: 1.0.2
  - text: 6.0.1
  - theming: 2.7.0
  - twofactor_backupcodes: 1.21.0
  - updatenotification: 1.22.0
  - user_oidc: 8.2.2
  - user_status: 1.12.0
  - viewer: 5.0.0-dev.0
  - webhook_listeners: 1.3.0
  - whiteboard: 1.5.0
  - workflowengine: 2.14.0
Disabled:
  - admin_audit: 1.22.0
  - app_api: 32.0.0 (installed 32.0.0)
  - dashboard: 7.12.0 (installed 7.12.0)
  - encryption: 2.20.0
  - files_external: 1.24.0
  - files_pdfviewer: 5.0.0-dev.0 (installed 5.0.0-dev.0)
  - firstrunwizard: 5.0.0-dev.0 (installed 5.0.0-dev.0)
  - survey_client: 4.0.0-dev.0 (installed 4.0.0-dev.0)
  - suspicious_login: 10.0.0-dev.0
  - twofactor_nextcloud_notification: 6.0.0-dev.0
  - twofactor_totp: 14.0.0
  - user_ldap: 1.23.0
  - weather_status: 1.12.0 (installed 1.12.0)

Nextcloud Signing status

No errors have been found.

Nextcloud Logs

{"reqId":"wpPeIFVjvS2H9N2XOhVP","level":3,"time":"2025-12-25T10:00:02+00:00","remoteAddr":"","user":"--","app":"no app in context","method":"","url":"--","message":"Error while sending notification to federation server: Client error: `POST https://[server B]/nc/ocm/notifications` resulted in a `400 Bad Request` response:\n{\"message\":\"Invalid signature\",\"validationErrors\":[]}\n","userAgent":"--","version":"32.0.1.2","exception":{"Exception":"GuzzleHttp\\Exception\\ClientException","Message":"Client error: `POST https://[server B]/nc/ocm/notifications` resulted in a `400 Bad Request` response:\n{\"message\":\"Invalid signature\",\"validationErrors\":[]}\n","Code":400,"Trace":[{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/Middleware.php","line":72,"function":"create","class":"GuzzleHttp\\Exception\\RequestException","type":"::","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/promises/src/Promise.php","line":209,"function":"GuzzleHttp\\{closure}","class":"GuzzleHttp\\Middleware","type":"::","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/promises/src/Promise.php","line":158,"function":"callHandler","class":"GuzzleHttp\\Promise\\Promise","type":"::"},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/promises/src/TaskQueue.php","line":52,"function":"GuzzleHttp\\Promise\\{closure}","class":"GuzzleHttp\\Promise\\Promise","type":"::","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/promises/src/Promise.php","line":251,"function":"run","class":"GuzzleHttp\\Promise\\TaskQueue","type":"->"},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/promises/src/Promise.php","line":227,"function":"invokeWaitFn","class":"GuzzleHttp\\Promise\\Promise","type":"->"},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/promises/src/Promise.php","line":272,"function":"waitIfPending","class":"GuzzleHttp\\Promise\\Promise","type":"->"},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/promises/src/Promise.php","line":229,"function":"invokeWaitList","class":"GuzzleHttp\\Promise\\Promise","type":"->"},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/promises/src/Promise.php","line":69,"function":"waitIfPending","class":"GuzzleHttp\\Promise\\Promise","type":"->"},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/Client.php","line":189,"function":"wait","class":"GuzzleHttp\\Promise\\Promise","type":"->"},{"file":"/var/www/nextcloud/lib/private/Http/Client/Client.php","line":277,"function":"request","class":"GuzzleHttp\\Client","type":"->"},{"file":"/var/www/nextcloud/lib/private/Federation/CloudFederationProviderManager.php","line":218,"function":"post","class":"OC\\Http\\Client\\Client","type":"->","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/lib/private/Federation/CloudFederationProviderManager.php","line":186,"function":"postOcmPayload","class":"OC\\Federation\\CloudFederationProviderManager","type":"->"},{"file":"/var/www/nextcloud/apps/spreed/lib/Federation/BackendNotifier.php","line":450,"function":"sendCloudNotification","class":"OC\\Federation\\CloudFederationProviderManager","type":"->"},{"file":"/var/www/nextcloud/apps/spreed/lib/Federation/BackendNotifier.php","line":555,"function":"sendUpdateToRemote","class":"OCA\\Talk\\Federation\\BackendNotifier","type":"->"},{"file":"/var/www/nextcloud/apps/spreed/lib/Federation/BackendNotifier.php","line":499,"function":"retrySendingFailedNotification","class":"OCA\\Talk\\Federation\\BackendNotifier","type":"->"},{"file":"/var/www/nextcloud/apps/spreed/lib/BackgroundJob/RetryNotificationsJob.php","line":31,"function":"retrySendingFailedNotifications","class":"OCA\\Talk\\Federation\\BackendNotifier","type":"->"},{"file":"/var/www/nextcloud/lib/public/BackgroundJob/Job.php","line":61,"function":"run","class":"OCA\\Talk\\BackgroundJob\\RetryNotificationsJob","type":"->"},{"file":"/var/www/nextcloud/lib/public/BackgroundJob/TimedJob.php","line":97,"function":"start","class":"OCP\\BackgroundJob\\Job","type":"->"},{"file":"/var/www/nextcloud/lib/public/BackgroundJob/TimedJob.php","line":84,"function":"start","class":"OCP\\BackgroundJob\\TimedJob","type":"->"},{"file":"/var/www/nextcloud/cron.php","line":175,"function":"execute","class":"OCP\\BackgroundJob\\TimedJob","type":"->"}],"File":"/var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/Exception/RequestException.php","Line":111,"message":"Error while sending notification to federation server: Client error: `POST https://[server B]/nc/ocm/notifications` resulted in a `400 Bad Request` response:\n{\"message\":\"Invalid signature\",\"validationErrors\":[]}\n","exception":[],"CustomMessage":"Error while sending notification to federation server: Client error: `POST https://[server B]/nc/ocm/notifications` resulted in a `400 Bad Request` response:\n{\"message\":\"Invalid signature\",\"validationErrors\":[]}\n"},"id":"694d0c1989518"}

Additional info

When trying to add user from federation to chat in Talk, error is from ocm/notifications
When trying to share calendar with user from federation, error is from ocm/shares

Start by reproducing the two-server setup in the listed steps, testing federated Calendar sharing and Talk conversations while confirming that federated file shares work. Compare the federation, calendar, and Talk app behavior and collect the relevant server logs; done means both reported federation features work across the two Nextcloud 32 servers.