I've encountered an intermittent deployment issue when deploying a monorepo application on Railway. Although the service is configured to use the backend/ directory as the root, some deployments appear to ignore the configured rootDirectory during the Nixpacks build step.

Environment

Railway

GitHub integration

Monorepo structure

Backend: Flask + Gunicorn

Frontend: React (separate directory)

Repository Structure

project/

├── frontend/

└── backend/

├── app.py

├── requirements.txt

└── railway.json

Expected Behavior

Railway should consistently build from the configured backend/ directory.

Actual Behavior

Occasionally, Nixpacks scans the repository root instead of the configured backend directory.

This results in build failures such as:

Unable to locate requirements.txt

Build image creation failure

Deployment stops before startup

Steps to Reproduce

Create a GitHub monorepo.

Place the backend inside a backend/ directory.

Configure Railway to use that directory as the root.

Push a commit.

Observe that some deployments build correctly while others ignore the configured root.