**Context:**
I’m running n8n self-hosted on Render, managing workflows via the **n8n MCP server** (Model Context Protocol for AI-assisted automation). The underlying issue is WAF blocking REST API calls, but the symptom first appeared as MCP tool failures.
**The Issue:**
When updating workflows that contain multiple Code nodes (3+) with JavaScript, requests return 403 Forbidden with a Cloudflare WAF block page. Smaller payloads with the same structure succeed.
**How it manifests:**
- **Via n8n MCP:** `n8n_update_full_workflow` or `n8n_create_workflow` fails with 403
- **Via REST API:** PUT `/api/v1/workflows/{id}` returns Cloudflare block page
- **Via n8n UI:** Works fine (same operations succeed)
**What I’ve Tried:**
- Smaller payloads (1-2 Code nodes): Works
- Manual updates via n8n UI: Works
- Incremental node addition via MCP: Sometimes blocked mid-sequence
**Environment:**
- n8n self-hosted on Render (Hobby plan)
- n8n MCP server for programmatic workflow management
- Also affects direct REST API calls
**Error:**
- HTTP 403 Forbidden
- Cloudflare WAF block page (not n8n API error)
- CF-RAY: `9c88dd08b97a0731`
**Questions:**
1. Anyone else using n8n MCP or REST API on Render hitting this?
2. Any known workarounds for programmatic workflow management?
3. Is there a way to request WAF tuning for specific endpoints?
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## How to Check if You’re Affected
1. Host n8n on Render
2. Use n8n MCP or REST API to create/update a workflow
3. Include 3+ Code nodes with `jsCode` parameters (~500+ chars each)
4. Total payload ~2.5KB+
5. Check if you get HTTP 403 with Cloudflare block page
**How to get your CF-RAY (trace ID):**
```bash
curl -i -X PUT “https://[your-service].onrender.com/api/v1/workflows/[id]” \
-H “Content-Type: application/json” \
-H “X-N8N-API-KEY: [key]” \
-d ‘{“name”:“test”,“nodes”:[…]}’ 2>&1 | grep -i “cf-ray”
```
Or check MCP error output - the CF-RAY may be in the response body.
**If you hit this issue**, please reply with:
- Your CF-RAY ID
- Your use case (n8n MCP, direct API, Claude Code, etc.)
More data points help Render prioritize a fix.
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**Support ticket submitted:** Via Render chatbox. no ticket number provided.