Configuration injection into MCP Servers run by Docker MCP Gateway

Based on information available in the Docker documentation I created a Docker compose file for Docker Gateway that works together with Claude Code running in the container.

name: Test

networks:
  development:
    name: development
    driver: bridge

services:
  traefik:
    container_name: traefik
    isolation: default
    image: traefik:v3.3.0-rc2
    command:
      - "--log.level=DEBUG"
      - "--accesslog=true"
      - "--api"
      - "--api.debug=true"
      - "--api.dashboard=true"
      - "--api.insecure=true"
      - "--providers.docker=true"
      - "--providers.docker.exposedbydefault=false"
      - "--providers.file.directory=/etc/traefik"
      - "--entryPoints.web.address=:80"
      - "--entryPoints.web.http.redirections.entryPoint.to=websecure"
      - "--entryPoints.websecure.address=:443"
      - "--entryPoints.websecure.proxyProtocol.insecure=true"
      - "--entryPoints.sqlserver.address=:1433"
      - "--entryPoints.sqlserver.proxyProtocol.insecure=true"
    ports:
      - "80:80"
      - "443:443"
      - "1433:1433"
      - "8080:8080"
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
      - ./traefik/config/dynamic/dynamic.yaml:/etc/traefik/dynamic.yaml:ro
      - ./certs:/etc/certs:ro
    networks:
      - development
    healthcheck:
      test: ["CMD", "traefik", "healthcheck", "--ping"]
    extra_hosts:
      - "host.docker.internal:host-gateway"
  
  claude:
    container_name: claude
    isolation: default
    build:
      dockerfile: .Dockerfile
      context: ./build/claude
      args:
        TZ: "America/Los_Angeles"
        CLAUDE_CODE_VERSION: "latest"
        GIT_DELTA_VERSION: "0.18.2"
        ZSH_IN_DOCKER_VERSION: "1.2.0"
    cap_add:
      - NET_ADMIN
      - NET_RAW
    user: node
    volumes:
      - ./data/claude/delegated:/delegated
      - ./data/claude/claude-code-bashhistory:/commandhistory
      - ./data/claude/claude-code-config:/home/node/.claude
      - ./data/claude/claude-root:/root/.claude
    environment:
      NODE_OPTIONS: "--max-old-space-size=4096"
      CLAUDE_CONFIG_DIR: "/home/node/.claude"
      POWERLEVEL9K_DISABLE_GITSTATUS: "true"
      MCP_HOST: http://mcp-gateway:8811/sse
    stdin_open: true
    tty: true
    restart: always
    networks:
      - development
    depends_on:
      - mcp-gateway
    extra_hosts:
      - "host.docker.internal:host-gateway"
  mcp-gateway:
    image: docker/mcp-gateway:latest
    ports:
      - 8811:8811
    use_api_socket: true
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    command:
      - --transport=sse
      - --port=8811
      - --servers=fetch,brave,curl,context7,playwright
      - --config=/mcp_config
      - --secrets=docker-desktop:/run/secrets/mcp_secret
      - --verbose
    configs:
      - mcp_config
    secrets:
      - mcp_secret
    networks:
      - development
    extra_hosts:
      - "host.docker.internal:host-gateway"
configs:
  mcp_config:
    content: |
      servers:
        fetch:
          ignore_robots_txt: true
          networks:
            - development
          extra_hosts:
            - "host.docker.internal:host-gateway"
        brave:
          networks:
            - development
          extra_hosts:
            - "host.docker.internal:host-gateway"
        curl:
          networks:
            - development
          extra_hosts:
            - "host.docker.internal:host-gateway"
        context7:
          networks:
            - development
          extra_hosts:
            - "host.docker.internal:host-gateway"
        playwright:
          networks:
            - development
          extra_hosts:
            - "host.docker.internal:host-gateway"

secrets:
  mcp_secret:
    file: ./data/mcp-gateway/mcp.env

I am trying to inject some configuration into the containers created by Docker MCP Gateway with MCP servers like one for Fetch MCP Server. No matter what I try it seems that configuration is kind of ignored.

Containers are created, Claude connects to MCPs too. Any suggestions?