Help: Deploy prebuilt Docker image via GitHub Actions without rebuild

Hi all, I’m trying to automate deployment of my Dockerized app to Railway using GitHub Actions.

Here’s what I’m doing:

1. Build the Docker image in GitHub Actions.
2. Push the image to Docker Hub (crawan/housori-server:latest).
3. Deploy the service on Railway using the Railway CLI with my Project Token.

Workflow snippet:

- name: Install Railway CLI
  run: |
    curl -fsSL https://railway.app/install.sh | sh
    export PATH="$HOME/.railway/bin:$PATH"

- name: Deploy to Railway
  run: railway deploy
  env:
    RAILWAY_TOKEN: ${{ secrets.RAILWAY_PROJECT_TOKEN }}

Problem:

• Railway shows errors in the dashboard:

  Nixpacks build failed
  No template specified

• I do not want Railway to build anything, just pull the Docker image from Docker Hub.
• Tried railway link, --service, --detach with Project Token, but it fails.
• Using User API Key is interactive and not safe for CI/CD.

What I want:

• Programmatically trigger Railway to roll out my prebuilt Docker image from Docker Hub using Project Token, without rebuilding.

Has anyone successfully done this in CI/CD? Any recommended workflow setup?