Why Claude's Custom Connector Failed on Cloudflare (and How I Fixed It)

TL;DR

I built a custom connector API on Cloudflare Workers that worked perfectly with ChatGPT but failed with Claude. The culprit? Cloudflare's "AI Bot" blocking feature. Turning it off in Security → Bots fixed the issue instantly.

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The Problem

I was building a custom connector that works with both ChatGPT and Claude. Hosted it on Cloudflare Workers, tested with ChatGPT—worked fine. Then I tried Claude with the exact same setup. Connection error. Every. Single. Time.

Same API, same endpoint, same configuration. Why would Claude fail when ChatGPT succeeded?

The Solution

Cloudflare's security settings were blocking Claude.

Specifically, under Security → Bots, the "Block AI Bots" option was set to "Block on all pages." Switching this to "Off" allowed Claude to connect immediately.

The Debugging Journey

Here's how I tracked down the issue:

Step 1: Initial Setup

Created the connector API on Cloudflare Workers and deployed it to a custom domain. Configured ChatGPT's connector feature, ran the connection test. Success. Requests were logged, responses were correct.

Step 2: Claude Fails

Set up Claude with the identical endpoint. Connection test failed with a generic "Cannot connect" error—no details, no hints.

Checked my configuration multiple times. Everything looked correct.

Step 3: Checking the Logs

This is where things got interesting. I opened Cloudflare Workers logs and found that Claude's requests never reached the Worker. ChatGPT's requests were logged, but nothing from Claude.

Step 4: Ruling Out Application Code

Maybe my code had some edge case? I rebuilt the entire app from scratch—just authentication, nothing else. Deployed it. Same result. Claude still couldn't connect.

So the application code wasn't the problem.

Step 5: The Breakthrough

On a hunch, I tried connecting using the default *.workers.dev URL instead of my custom domain.

It worked.

Same app, same Claude configuration—different URL. That was the clue I needed. The issue had to be domain-specific.

Step 6: Finding the Setting

Went to Cloudflare Dashboard → Security → Bots. Found "Block AI Bots" enabled with "Block on all pages" selected.

Changed it to "Off," saved, and ran Claude's connection test again.

Success. Finally.

Why This Happened

Cloudflare treats different AI services' User-Agents differently. ChatGPT apparently wasn't flagged, but Claude was. This makes sense for protecting regular websites from AI scraping, but it breaks legitimate API integrations.

The *.workers.dev domain doesn't inherit your custom domain's security settings, which is why it worked as a bypass.

Key Takeaway

If you're hosting a custom connector on Cloudflare and Claude won't connect:

1. Go to Security → Bots in your Cloudflare dashboard
2. Find "Block AI Bots"
3. Set it to Off

That's it. A 30-second fix for hours of debugging.

Conclusion

The frustrating part was that ChatGPT worked fine, which sent me down the wrong debugging path. I assumed the issue was Claude-specific—maybe different auth requirements, maybe a bug in my code.

Turns out it was just Cloudflare doing its job a little too well.

Hope this saves someone else the headache.