n8n-openai-adapter

An OpenAI-compatible HTTP adapter that exposes self-hosted n8n chat agents behind a standard /v1/chat/completions API, so any OpenAI client (Cursor, LibreChat, the openai SDK, a custom app) can talk to your n8n agents as if they were OpenAI models.

n8n itself does not ship an inbound OpenAI-compatible endpoint (its "AI Gateway" is an outbound proxy to n8n Cloud). This small Elixir service is the bridge: one /v1/chat/completions endpoint, routed to whichever n8n agent you name in the model field.

How it works

Your OpenAI client
   POST /v1/chat/completions {"model":"scholar-agent","thread_id":"abc","messages":[...]}
        |
        v
   n8n-openai-adapter (Plug + Bandit)
     - authorize (Bearer <ADAPTER_API_KEY>)
     - look up "scholar-agent" -> n8n chat webhook URL (AgentRegistry GenServer)
     - take the last user message
     - forward to the n8n webhook {sessionId: thread_id, action: sendMessage, chatInput}
        |
        v
   n8n agent (its MCP tools, memory, etc. run as usual)
        |
        v
   returns OpenAI-shaped {"choices":[{"message":{"role":"assistant","content":...}}]}

Multiple agents = multiple model names, each mapped to a different n8n webhook in the AGENTS env var.

Configuration (env vars)

Var	Required	Purpose
AGENTS	seed	JSON map of model -> n8n chat webhook URL used to seed the store on first boot. e.g. {"scholar-agent":"https://..."}
ADAPTER_API_KEY	yes	Bearer key that OpenAI clients send.
ADMIN_API_KEY	yes	Bearer key for the admin API (manage agents at runtime).
AGENTS_FILE	no	Path to the JSON store (default /var/lib/n8n-openai/agents.json).
PORT	no	HTTP port (default 8000).
CHAT_WEBHOOK_BASIC	no	"user:password" if your n8n Chat Trigger is Basic-auth protected.

Admin API (manage agents at runtime)

Agents are persisted to AGENTS_FILE and can be added/removed without a redeploy, using the ADMIN_API_KEY:

# list
curl -H "Authorization: Bearer $ADMIN_API_KEY" https://openai.bueso.eu/admin/agents

# add / update an agent
curl -X POST -H "Authorization: Bearer $ADMIN_API_KEY" -H "Content-Type: application/json" \
  -d '{"model":"media-agent","webhook":"https://n8n.bueso.eu/webhook/<id>/chat"}' \
  https://openai.bueso.eu/admin/agents

# remove
curl -X DELETE -H "Authorization: Bearer $ADMIN_API_KEY" \
  https://openai.bueso.eu/admin/agents/media-agent

The AGENTS env var only seeds the store on first boot; after that the file is authoritative.

Building & running

mix deps.get
mix compile
ADAPTER_API_KEY=secret AGENTS='{"scholar-agent":"https://n8n.bueso.eu/webhook/<id>/chat"}' \
  PORT=8000 mix run --no-halt

Testing

MIX_ENV=test mix test

Nix

The repo ships a flake.nix exporting overlays.default and a packages.default (the packaged BEAM release), so it can be consumed as a flake input from your NixOS config just like any other flake — e.g.:

inputs.n8n-openai-adapter.url = "git+https://gitea.bueso.eu/<owner>/n8n-openai-adapter";