[Bug]: Socket.IO server intercepts Strapi Transfer WebSocket upgrade, causing 504 on proxied host DigitalOcean App Platform)

[otemu]

What issue are you experiencing?

When strapi-plugin-io is enabled on a reverse-proxied host DigitalOcean App Platform, running strapi transfer --to <remote> fails immediately with:

[FATAL] Failed to initialize the connection: Unexpected server response 504

Disabling the plugin (enabled: false) allows the transfer to complete successfully every time, confirming plugin-io is the source of the conflict.

Suspected cause: engine.io attaches a raw upgrade event listener directly to the underlying HTTP server. On a reverse-proxied host this listener appears to intercept WebSocket upgrade requests destined for Strapi's transfer endpoint (/admin/transfer/runner/push) before they can be handled, returning an unexpected response that the proxy surfaces as a 504.

Steps To Reproduce

1. Deploy a Strapi v5 app with strapi-plugin-io enabled to DigitalOcean App Platform
2. Run: yarn strapi transfer --to https://<your-app>.ondigitalocean.app/admin --exclude files
3. See error: [FATAL] Failed to initialize the connection: Unexpected server response 504
4. Set enabled: false on the plugin and repeat step 2 — transfer completes successfully

What version of the plugin are you using?

5.8.2

What strapi version are you using?

5.45.0

[Schero94]

I’ll fix it. Thanks for reaching out. :)