No preview in public conversations when not logged in (guest)

> [!TIP]
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---


This looks like a regression of old and closed issues, for example #4471 or #2309.

## Steps to reproduce

1. In Talk, use "Create a new conversation"
  * With default type
  * Activate "Allow guest to join by link"
  * And "Create the conversation"
2. Add a JPEG image from your local disk ("Upload from device") to the conversation
3. Connect to the conversation from another browser or from a private window (as a guest)
4. The image is there but **no preview is available**
       The following URL (example) gets a 500 error and no other detail:
        https://mysite/apps/files_sharing/publicpreview/roL68HA6983KtHw?x=-1&y=384&a=1

Additional steps:
5. Click on the image, it opens a public share where the image is displayed
6. In that new context the preview is visible
    The associated URL (example) is:
     https://mysite/apps/files_sharing/publicpreview/roL68HA6983KtHw?file=%2FIMG_20260823_190436.jpg&x=32&y=32&mimeFallback=true&v=858990&a=0
7. If I add (using curl) "file=<value>" to the first (failing) URL above, it works
8. All the previews work correctly if the user is logged in. The problem above only occurs for guests

_Alternative scenario_: same as above but using "Share from Files" (globally this should be checked with all the ways to share items).


### Expected behaviour
The previews should work for guests of public conversations.

### Actual behaviour
The previews in the public conversations fail when files were shared with "Upload from device"

_Alternative scenario_: Some of the previews in the public conversations fail when files were shared with "Share from Files"

## Talk app

**Talk app version:** 24.0.4

**Custom Signaling server configured:** no

**Custom TURN server configured:** no

**Custom STUN server configured:** no


## Browser

**Microphone available:** no

**Camera available:** no

**Operating system:** Ubuntu

**Browser name:** Firefox/Chromium

**Browser version:** Firefox 154/ Chromium 152

### Browser log

Failed to load resource: the server responded with a status of 500 ()
GET
https://mysite/apps/files_sharing/publicpreview/roL68HA6983KtHw?x=-1&y=384&a=1
[HTTP/2 500  96ms]

(same kind of log for the _alternative scenario_)

## Server configuration

**Operating system**: Debian (host that runs nextcloud through helm)

**Web server:** Apache/Nginx

**Database:** PostgreSQL

**PHP version:** 8.5.10

**Nextcloud Version:** 34.0.3

**List of activated apps:**

<details>

```
Enabled:
  - activity: 7.0.0
  - app_api: 34.0.0
  - appstore: 1.0.0
  - bruteforcesettings: 7.0.0
  - circles: 34.0.0
  - cloud_federation_api: 1.18.0
  - comments: 1.24.0
  - contactsinteraction: 1.15.0
  - dashboard: 7.14.0
  - dav: 1.40.0
  - federatedfilesharing: 1.24.0
  - federation: 1.24.0
  - files: 2.6.0
  - files_downloadlimit: 5.2.0
  - files_lock: 34.0.1
  - files_pdfviewer: 7.0.0-dev.0
  - files_reminders: 1.7.0
  - files_sharing: 1.26.0
  - files_sharing_raw: 0.7.2
  - files_trashbin: 1.24.0
  - files_versions: 1.27.0
  - firstrunwizard: 7.0.0-dev.0
  - logreader: 7.0.0
  - lookup_server_connector: 1.22.0
  - nextcloud_announcements: 6.0.0
  - notifications: 7.0.0-dev.1
  - oauth2: 1.22.0
  - office: 1.0.0
  - password_policy: 6.0.0-dev.0
  - photos: 7.0.0
  - privacy: 6.0.0-dev.1
  - profile: 1.3.0
  - provisioning_api: 1.24.0
  - recommendations: 7.0.0
  - related_resources: 5.0.0-dev.0
  - richdocuments: 11.1.0
  - serverinfo: 6.0.0
  - settings: 1.17.0
  - sharebymail: 1.24.0
  - spreed: 24.0.4
  - support: 6.0.0
  - survey_client: 6.0.0-dev.0
  - systemtags: 1.24.0
  - text: 8.0.0
  - theming: 2.9.0
  - theming_customcss: 1.21.0
  - twofactor_backupcodes: 1.23.0
  - twofactor_totp: 16.0.0
  - updatenotification: 1.24.0
  - user_status: 1.14.0
  - viewer: 7.0.0-dev.0
  - weather_status: 1.14.0
  - webhook_listeners: 1.6.0
  - workflowengine: 2.16.0
Disabled:
  - admin_audit: 1.24.0
  - encryption: 2.22.0
  - files_external: 1.26.0
  - suspicious_login: 12.0.0-dev.0
  - twofactor_nextcloud_notification: 8.0.0
  - user_ldap: 1.25.0
```
</details>

**Nextcloud configuration:**

<details>

```
{
    "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
            }
        ],
        "mail_smtpmode": "smtp",
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "587",
        "mail_smtpsecure": "tls",
        "mail_smtpauth": true,
        "mail_smtpauthtype": "LOGIN",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_from_address": "***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",
            "<my host>"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "pgsql",
        "version": "34.0.3.2",
        "overwrite.cli.url": "https:\/\/<my host>",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbtableprefix": "oc_",
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "updater.server.url": "***REMOVED SENSITIVE VALUE***",
        "loglevel": 2,
        "log_type": "syslog",
        "mail_smtptimeout": 30,
        "overwriteprotocol": "https",
        "mail_smtpdebug": false,
        "maintenance": false,
        "syslog_tag": "Nextcloud",
        "logfile": "",
        "openmetrics_allowed_clients": [
            "127.0.0.1",
            "10.42.0.0\/16",
            "10.43.0.0\/16"
        ],
        "enabledPreviewProviders": {
            "0": "OC\\Preview\\Movie",
            "1": "OC\\Preview\\MP4",
            "2": "OC\\Preview\\AVI",
            "3": "OC\\Preview\\MKV",
            "4": "OC\\Preview\\MOV",
            "5": "OC\\Preview\\Image",
            "6": "OC\\Preview\\PNG",
            "7": "OC\\Preview\\JPEG",
            "8": "OC\\Preview\\GIF",
            "9": "OC\\Preview\\HEIC",
            "11": "OC\\Preview\\JPG"
        },
        "backgroundjobs_mode": "cron",
        "update_check": false,
        "simpleSignUpLink.shown": false,
        "app_install_overwrite": [],
        "DB_PORT": "5432"
    }
}
```
</details>

### Server log (data/nextcloud.log)
<details>

```
{"reqId":"z8P6WciD4t2fhx0WgRaz","level":3,"time":"2026-09-03 07:16:37","remoteAddr":"192.168.193.165","user":"--","app":"index","method":"GET","url":"/apps/files_sharing/publicpreview/roL68HA6983KtHw?x=-1&y=384&a=1","scriptName":"/index.php","message":"OC\\PreviewManager::getPreview(): Argument #1 ($file) must be of type OCP\\Files\\File, OC\\Files\\Node\\Folder given, called in /var/www/html/apps/files_sharing/lib/Controller/PublicPreviewController.php on line 133 in file '/var/www/html/lib/private/PreviewManager.php' line 171","userAgent":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/152.0.0.0 Safari/537.36","version":"34.0.3.2","exception":{"Exception":"Exception","Message":"OC\\PreviewManager::getPreview(): Argument #1 ($file) must be of type OCP\\Files\\File, OC\\Files\\Node\\Folder given, called in /var/www/html/apps/files_sharing/lib/Controller/PublicPreviewController.php on line 133 in file '/var/www/html/lib/private/PreviewManager.php' line 171","Code":0,"Trace":[{"file":"/var/www/html/lib/private/AppFramework/App.php","line":137,"function":"dispatch","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Files_Sharing\\Controller\\PublicPreviewController"},"getPreview"]},{"file":"/var/www/html/lib/private/Route/Router.php","line":324,"function":"main","class":"OC\\AppFramework\\App","type":"::","args":["OCA\\Files_Sharing\\Controller\\PublicPreviewController","getPreview",{"__class__":"OC\\AppFramework\\DependencyInjection\\DIContainer"},{"_route":"files_sharing.publicpreview.getpreview","token":"roL68HA6983KtHw"}]},{"file":"/var/www/html/lib/base.php","line":1172,"function":"match","class":"OC\\Route\\Router","type":"->","args":["/apps/files_sharing/publicpreview/roL68HA6983KtHw"]},{"file":"/var/www/html/index.php","line":25,"function":"handleRequest","class":"OC","type":"::","args":[]}],"File":"/var/www/html/lib/private/AppFramework/Http/Dispatcher.php","Line":110,"Previous":{"Exception":"TypeError","Message":"OC\\PreviewManager::getPreview(): Argument #1 ($file) must be of type OCP\\Files\\File, OC\\Files\\Node\\Folder given, called in /var/www/html/apps/files_sharing/lib/Controller/PublicPreviewController.php on line 133","Code":0,"Trace":[{"file":"/var/www/html/apps/files_sharing/lib/Controller/PublicPreviewController.php","line":133,"function":"getPreview","class":"OC\\PreviewManager","type":"->","args":[{"__class__":"OC\\Files\\Node\\Folder"},-1,384,false]},{"file":"/var/www/html/lib/private/AppFramework/Http/Dispatcher.php","line":165,"function":"getPreview","class":"OCA\\Files_Sharing\\Controller\\PublicPreviewController","type":"->","args":["roL68HA6983KtHw",{"__class__":"OC\\Files\\Node\\Folder"},-1,384,true,false]},{"file":"/var/www/html/lib/private/AppFramework/Http/Dispatcher.php","line":78,"function":"executeController","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Files_Sharing\\Controller\\PublicPreviewController"},"getPreview"]},{"file":"/var/www/html/lib/private/AppFramework/App.php","line":137,"function":"dispatch","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Files_Sharing\\Controller\\PublicPreviewController"},"getPreview"]},{"file":"/var/www/html/lib/private/Route/Router.php","line":324,"function":"main","class":"OC\\AppFramework\\App","type":"::","args":["OCA\\Files_Sharing\\Controller\\PublicPreviewController","getPreview",{"__class__":"OC\\AppFramework\\DependencyInjection\\DIContainer"},{"_route":"files_sharing.publicpreview.getpreview","token":"roL68HA6983KtHw"}]},{"file":"/var/www/html/lib/base.php","line":1172,"function":"match","class":"OC\\Route\\Router","type":"->","args":["/apps/files_sharing/publicpreview/roL68HA6983KtHw"]},{"file":"/var/www/html/index.php","line":25,"function":"handleRequest","class":"OC","type":"::","args":[]}],"File":"/var/www/html/lib/private/PreviewManager.php","Line":171},"message":"OC\\PreviewManager::getPreview(): Argument #1 ($file) must be of type OCP\\Files\\File, OC\\Files\\Node\\Folder given, called in /var/www/html/apps/files_sharing/lib/Controller/PublicPreviewController.php on line 133 in file '/var/www/html/lib/private/PreviewManager.php' line 171","exception":"{\"class\":\"Exception\",\"message\":\"OC\\PreviewManager::getPreview(): Argument #1 ($file) must be of type OCP\\Files\\File, OC\\Files\\Node\\Folder given, called in /var/www/html/apps/files_sharing/lib/Controller/PublicPreviewController.php on line 133 in file '/var/www/html/lib/private/PreviewManager.php' line 171\",\"code\":0,\"file\":\"/var/www/html/lib/private/AppFramework/Http/Dispatcher.php:110\",\"trace\":\"#0 /var/www/html/lib/private/AppFramework/App.php(137): OC\\AppFramework\\Http\\Dispatcher->dispatch(Object(OCA\\Files_Sharing\\Controller\\PublicPreviewController), 'getPreview')\\n#1 /var/www/html/lib/private/Route/Router.php(324): OC\\AppFramework\\App::main('OCA\\\\Files_Shari...', 'getPreview', Object(OC\\AppFramework\\DependencyInjection\\DIContainer), Array)\\n#2 /var/www/html/lib/base.php(1172): OC\\Route\\Router->match('/apps/files_sha...')\\n#3 /var/www/html/index.php(25): OC::handleRequest()\\n#4 {main}\",\"previous\":{\"class\":\"TypeError\",\"message\":\"OC\\PreviewManager::getPreview(): Argument #1 ($file) must be of type OCP\\Files\\File, OC\\Files\\Node\\Folder given, called in /var/www/html/apps/files_sharing/lib/Controller/PublicPreviewController.php on line 133\",\"code\":0,\"file\":\"/var/www/html/lib/private/PreviewManager.php:171\",\"trace\":\"#0 /var/www/html/apps/files_sharing/lib/Controller/PublicPreviewController.php(133): OC\\PreviewManager->getPreview(Object(OC\\Files\\Node\\Folder), -1, 384, false)\\n#1 /var/www/html/lib/private/AppFramework/Http/Dispatcher.php(165): OCA\\Files_Sharing\\Controller\\PublicPreviewController->getPreview('roL68HA6983KtHw', Object(OC\\Files\\Node\\Folder), -1, 384, true, false)\\n#2 /var/www/html/lib/private/AppFramework/Http/Dispatcher.php(78): OC\\AppFramework\\Http\\Dispatcher->executeController(Object(OCA\\Files_Sharing\\Controller\\PublicPreviewController), 'getPreview')\\n#3 /var/www/html/lib/private/AppFramework/App.php(137): OC\\AppFramework\\Http\\Dispatcher->dispatch(Object(OCA\\Files_Sharing\\Controller\\PublicPreviewController), 'getPreview')\\n#4 /var/www/html/lib/private/Route/Router.php(324): OC\\AppFramework\\App::main('OCA\\\\Files_Shari...', 'getPreview', Object(OC\\AppFramework\\DependencyInjection\\DIContainer), Array)\\n#5 /var/www/html/lib/base.php(1172): OC\\Route\\Router->match('/apps/files_sha...')\\n#6 /var/www/html/index.php(25): OC::handleRequest()\\n#7 {main}\"}}","CustomMessage":"OC\\PreviewManager::getPreview(): Argument #1 ($file) must be of type OCP\\Files\\File, OC\\Files\\Node\\Folder given, called in /var/www/html/apps/files_sharing/lib/Controller/PublicPreviewController.php on line 133 in file '/var/www/html/lib/private/PreviewManager.php' line 171"}}
```
</details>

When using the _alternative scenario_:
<details>
```
{
  "reqId": "8wj42mLCTFmiVKGVyd2d",
  "level": 3,
  "time": "2026-09-03 07:33:14",
  "remoteAddr": "192.168.193.165",
  "user": "--",
  "app": "index",
  "method": "GET",
  "url": "/apps/files_sharing/publicpreview/tRD7CooDggB9EYo?x=-1&y=384&a=1",
  "scriptName": "/index.php",
  "message": "An exception occurred while executing a query: SQLSTATE[42702]: Ambiguous column: 7 ERROR:  column reference \"file_id\" is ambiguous\nLINE 1: ...rsions\" \"v\" ON \"p\".\"version_id\" = \"v\".\"id\" WHERE (\"file_id\" ...\n                                                             ^",
  "userAgent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/152.0.0.0 Safari/537.36",
  "version": "34.0.3.2",
  "exception": {
    "Exception": "OC\\DB\\Exceptions\\DbalException",
    "Message": "An exception occurred while executing a query: SQLSTATE[42702]: Ambiguous column: 7 ERROR:  column reference \"file_id\" is ambiguous\nLINE 1: ...rsions\" \"v\" ON \"p\".\"version_id\" = \"v\".\"id\" WHERE (\"file_id\" ...\n                                                             ^",
    "Code": 7,
    "Trace": [
      {
        "file": "/var/www/html/lib/private/DB/ConnectionAdapter.php",
        "line": 60,
        "function": "wrap",
        "class": "OC\\DB\\Exceptions\\DbalException",
        "type": "::",
        "args": [
          {
            "__class__": "Doctrine\\DBAL\\Exception\\NonUniqueFieldNameException"
          },
          "",
          "SELECT `p`.*, `l`.`bucket_name`, `l`.`object_store_name`, `v`.`version` FROM `*PREFIX*previews` `p` LEFT JOIN `*PREFIX*preview_locations` `l` ON `p`.`location_id` = `l`.`id` LEFT JOIN `*PREFIX*preview_versions` `v` ON `p`.`version_id` = `v`.`id` WHERE (`file_id` = :dcValue1) AND (`width` = :dcValue2) AND (`height` = :dcValue3) AND (`mimetype_id` = :dcValue4) AND (`cropped` = :dcValue5) AND (`version_id` = :dcValue6)"
        ]
      },
      {
        "file": "/var/www/html/lib/private/DB/QueryBuilder/QueryBuilder.php",
        "line": 261,
        "function": "executeQuery",
        "class": "OC\\DB\\ConnectionAdapter",
        "type": "->",
        "args": [
          "SELECT `p`.*, `l`.`bucket_name`, `l`.`object_store_name`, `v`.`version` FROM `*PREFIX*previews` `p` LEFT JOIN `*PREFIX*preview_locations` `l` ON `p`.`location_id` = `l`.`id` LEFT JOIN `*PREFIX*preview_versions` `v` ON `p`.`version_id` = `v`.`id` WHERE (`file_id` = :dcValue1) AND (`width` = :dcValue2) AND (`height` = :dcValue3) AND (`mimetype_id` = :dcValue4) AND (`cropped` = :dcValue5) AND (`version_id` = :dcValue6)",
          {
            "dcValue1": 137,
            "dcValue2": 1024,
            "dcValue3": 576,
            "dcValue4": 10,
            "dcValue5": false,
            "0": "And 1 more entries, set log level to debug to see all entries"
          },
          {
            "dcValue1": 2,
            "dcValue2": 2,
            "dcValue3": 2,
            "dcValue4": 2,
            "dcValue5": 2,
            "0": "And 1 more entries, set log level to debug to see all entries"
          }
        ]
      },
(...)
}
```
</details>

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Uh oh!

No preview in public conversations when not logged in (guest) #19247

How to use GitHub

Steps to reproduce

Expected behaviour

Actual behaviour

Talk app

Browser

Browser log

Server configuration

Server log (data/nextcloud.log)

Metadata

Assignees

Labels

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Projects

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Relationships

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Uh oh!

No preview in public conversations when not logged in (guest) #19247

Description

How to use GitHub

Steps to reproduce

Expected behaviour

Actual behaviour

Talk app

Browser

Browser log

Server configuration

Server log (data/nextcloud.log)

Activity

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions