Public API endpoints return "Invalid URL" while openapi.yml and UI endpoints work

[leolionart]

Bug description

On a self-hosted n8n instance, every tested Public API endpoint under /api/v1/* returns:

{"message":"Invalid URL"}

At the same time:

• /api/v1/openapi.yml returns successfully
• /healthz returns successfully
• UI/internal endpoints like /rest/settings return successfully

This makes the Public API unusable for tools like n8n-mcp, even though the instance itself is reachable and the OpenAPI spec is served correctly.

To reproduce

Environment is self-hosted behind reverse proxy. Public host has been redacted below.

Example requests:

curl -i -H "X-N8N-API-KEY: <redacted>" "http://172.16.x.x:5678/api/v1/workflows?limit=3"
curl -i -H "X-N8N-API-KEY: <redacted>" "http://172.16.x.x:5678/api/v1/projects"
curl -i -H "X-N8N-API-KEY: <redacted>" "http://172.16.x.x:5678/api/v1/users"

All of the above return:

HTTP/1.1 400 Bad Request
Content-Type: application/json; charset=utf-8

{"message":"Invalid URL"}

But these succeed:

curl -i "http://172.16.x.x:5678/healthz"
curl -i "http://172.16.x.x:5678/rest/settings"
curl -i "http://172.16.x.x:5678/api/v1/openapi.yml"

Expected behavior

Public API endpoints such as /api/v1/workflows, /api/v1/projects, /api/v1/users, etc. should return valid JSON responses instead of 400 Invalid URL.

Observed behavior

• GET /api/v1/openapi.yml -> 200 OK
• GET /healthz -> 200 OK
• GET /rest/settings -> 200 OK
• All tested GET /api/v1/* resource endpoints -> 400 {\"message\":\"Invalid URL\"}

n8n setup

Self-hosted with env vars along these lines:

N8N_HOST=n8n.example.com
N8N_PROTOCOL=https
N8N_PORT=5678
WEBHOOK_URL=https://n8n.example.com/
N8N_EDITOR_BASE_URL=https://n8n.example.com
N8N_PROXY_HOPS=1

Also tested direct internal access by IP (http://172.16.x.x:5678) to bypass CDN / external proxy behavior. Same result.

Additional context

This does not appear to be caused by Cloudflare/CDN or the external reverse proxy, because reproducing directly against the internal IP shows the same behavior.

It also does not seem limited to the workflows route. The same Invalid URL response happens for multiple Public API resources.

If useful, I can provide sanitized logs from the main n8n container.

[n8n-assistant]

Hey @leolionart,

Thank you for reaching out! We’ve received your issue and are looking into it. To help us track this internally, we’ve created a Linear ticket with the reference: "GHC-7566".

We’ll keep you updated as we make progress, but if you have any additional details or context to share, feel free to add them here - it’s always helpful!

Thanks for your patience and for bringing this to our attention.

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For INTERNAL use only: GHC-7566