n8n

Driving CEL from n8n

This page shows how to drive CEL from n8n.

Read docs/adapters-cel-agents.md first if you haven't.

Purpose

n8n is a workflow automation platform. It does not speak MCP natively, so CEL needs a bridge. Two paths:

1. Execute Command node → cellar CLI. Works today. Each step is a shell invocation. Good for deterministic, short workflows.
2. HTTP Request node → cellar-worker. Planned. Uses the Phase 1 worker protocol (docs/worker-protocol.md). Good for long-running goals and remote execution. Not yet shipped — tracked on the roadmap.

This document covers both. Path 1 is usable now.

Ownership

• n8n owns: the workflow graph, branching, error routing, retries, and scheduling.
• CEL owns: execution of each goal or action.
• Adapters own: app-specific truth (Numbers cells etc.).

Because n8n is a workflow engine, not an LLM agent, it typically either:

• (a) hands CEL a full natural-language goal and lets cel_think run_goal drive autonomously, or
• (b) hands CEL discrete actions produced by some upstream LLM node (e.g. an OpenAI node) and composes them with cel_act.

Mode (a) is the simplest integration and is what the examples below show.

Path 1: Execute Command → cellar CLI (works today)

Setup

1. Build CEL on the machine running n8n:

   cd /path/to/cellar && pnpm install && pnpm -r build
   

2. Make sure cellar is on PATH (or reference it by absolute path in the n8n node).
3. Grant macOS Accessibility permission to whichever process n8n uses to shell out (e.g. node, docker, or the n8n desktop app).
4. If you use cel_think run_goal from the CLI, set CEL_LLM_PROVIDER, CEL_LLM_API_KEY, and CEL_LLM_MODEL in the n8n environment.

Example n8n Workflow Snippet

Minimal workflow: manual trigger → Execute Command node that runs a CEL goal → Set node that surfaces the result.

{
  "nodes": [
    {
      "parameters": {},
      "id": "trigger",
      "name": "Manual Trigger",
      "type": "n8n-nodes-base.manualTrigger",
      "typeVersion": 1,
      "position": [240, 300]
    },
    {
      "parameters": {
        "command": "cellar run-goal \"Open Numbers and write BTC in A1\" --json"
      },
      "id": "cel-run",
      "name": "CEL Run Goal",
      "type": "n8n-nodes-base.executeCommand",
      "typeVersion": 1,
      "position": [520, 300]
    },
    {
      "parameters": {
        "values": {
          "string": [
            { "name": "result", "value": "={{ $json.stdout }}" }
          ]
        }
      },
      "id": "result",
      "name": "Result",
      "type": "n8n-nodes-base.set",
      "typeVersion": 2,
      "position": [800, 300]
    }
  ],
  "connections": {
    "Manual Trigger": { "main": [[{ "node": "CEL Run Goal", "type": "main", "index": 0 }]] },
    "CEL Run Goal": { "main": [[{ "node": "Result", "type": "main", "index": 0 }]] }
  }
}