Can't open OnlyOffice viewer/editor inside of Sync-In

[AkilisUi]

Hey,
First off, thanks for the wonderful app. It works flawlessly and I really look forward to use it more in depth.

I've been facing this issue for a few days now, though. I can't get to show OnlyOffice inside of Sync-In as the browser will show an error that basically says "OnlyOffice (docs.domain.tld) won't let the browser show the page if it is integrated in another website.". I've tried it on Firefox and Opera so far, using a distro based on Ubuntu 25.

I've setup an external OnlyOffice docker container, enabled it in Sync-in with the right options through the env and compose files and it seems to communicate. OnlyOffice Docs works fine on its own. So I guess I'm missing something crucial to allow Sync-In to integrate and show OnlyOffice.

My Sync-In compose :

#include:
#  - ./config/nginx/docker-compose.nginx.yaml
#  - ./config/onlyoffice/docker-compose.onlyoffice.yaml
#  - ./config/collabora/docker-compose.collabora.yaml
#  - ./config/sync-in-desktop-releases/docker-compose.sync-in-desktop-releases.yaml

name: sync-in
services:
  sync_in:
    image: syncin/server:1
    container_name: sync-in
    restart: always
    environment:
      - INIT_ADMIN
      - INIT_ADMIN_PASSWORD
      - INIT_ADMIN_LOGIN
      - PUID=${PUID:-8888}
      - PGID=${PGID:-8888}
    ports:
      - "380:8080"
    volumes:
      - ./environment.yaml:/app/environment/environment.yaml
      - data:/app/data
      - desktop_releases:/app/static/releases:ro
    depends_on:
      - mariadb
    logging:
      driver: json-file
      options:
        max-size: "25m"
        max-file: "5"
    networks:
      - sync_in_network

  mariadb:
    image: mariadb:11
    container_name: mariasyncin
    restart: always
    command: --innodb_ft_cache_size=16000000 --max-allowed-packet=1G
    environment:
      MYSQL_ROOT_PASSWORD: secret
      MYSQL_DATABASE: sync_in
    volumes:
      - mariadb_data:/var/lib/mysql
    networks:
      - sync_in_network

networks:
  sync_in_network:
    driver: bridge

volumes:
  data:
  mariadb_data:
  desktop_releases:

My Sync-In env file :

mysql:
  url: mysql://root:secret@mariadb:3306/sync_in
auth:
  encryptionKey: secret
  token:
    access:
      secret: secret
    refresh:
      secret: secret
applications:
  files:
    dataPath: /app/data
    collabora:
      enabled: false
    onlyoffice:
      enabled: true
      externalServer: https://docs.elikaserver.ovh
      verifySSL: true
      secret: secret

My OnlyOffice compose :

services:
  onlyoffice-documentserver:
    build:
      context: .
    image: onlyoffice/documentserver #[-de,-ee]
    container_name: onlyoffice-documentserver
    depends_on:
      - onlyoffice-postgresql
      - onlyoffice-rabbitmq
    environment:
      - DB_TYPE=postgres
      - DB_HOST=onlyoffice-postgresql
      - DB_PORT=5432
      - DB_NAME=onlyoffice
      - DB_USER=onlyoffice
      - AMQP_URI=amqp://guest:guest@onlyoffice-rabbitmq
      # Uncomment strings below to enable the JSON Web Token validation.
      - JWT_ENABLED=true
      - JWT_SECRET=secret
      - JWT_HEADER=Authorization
      - JWT_IN_BODY=true
    entrypoint:
     - "sh"
     - "-c"
     - |
       echo 'change nginx conf to req https..'
       sed -i "s/[$]the_scheme[;]/https;/g" /etc/onlyoffice/documentserver/nginx/includes/http-common.conf
       echo 'done! starting server...'
       /app/ds/run-document-server.sh
    ports:
      - '580:80'
      - '5443:443'
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:8000/info/info.json"]
      interval: 30s
      retries: 5
      start_period: 60s
      timeout: 10s
    stdin_open: true
    restart: always
    stop_grace_period: 60s
    volumes:
       - /var/www/onlyoffice/Data
       - /var/log/onlyoffice
       - /var/lib/onlyoffice/documentserver/App_Data/cache/files
       - /var/www/onlyoffice/documentserver-example/public/files
       - /usr/share/fonts

  onlyoffice-rabbitmq:
    container_name: onlyoffice-rabbitmq
    image: rabbitmq:3
    restart: always
    expose:
      - '5672'
    healthcheck:
      test: ["CMD", "rabbitmq-diagnostics", "status"]
      interval: 10s
      retries: 3
      start_period: 10s
      timeout: 10s

  onlyoffice-postgresql:
    container_name: onlyoffice-postgresql
    image: postgres:15
    environment:
      - POSTGRES_DB=onlyoffice
      - POSTGRES_USER=onlyoffice
      - POSTGRES_HOST_AUTH_METHOD=trust
    restart: always
    expose:
      - '5432'
    volumes:
      - postgresql_data:/var/lib/postgresql
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U onlyoffice"]
      interval: 10s
      retries: 3
      start_period: 10s
      timeout: 10s

volumes:
  postgresql_data:

I thought the situation was similar to #28 but I had no luck trying to integrate the OnlyOffice part inside of the Sync-In compose and adding the "entrypoint" thingy didn't work out for me either.

Any kind of help appreciated !

[AkilisUi]

After a few more digging into this subject, I finally found an answer to my questions and problems.

I'm using CosmosCloud (incredible project, check it out) for managing my dockers instances (more or less) and reverse proxying the apps.
I had to disable the headers hardening option in the settings of my OnlyOfficeDocs URL (the one that's reverse proxied). It then lets Sync-In integrate the OnlyOfficeDocs interface without any issue.

If anyone's having problems with this kind of configuration (with NPM, Pangolin or whatever), find a way to tweak the headers thingy. I've come across multiple topics for multiple reverse proxy apps across my journey.