Executor MCP on Cloudflare Access

Live deployment

Worker URL

https://executor-cloudflare.davis-benjamin41902.workers.dev

MCP endpoint

https://executor-cloudflare.davis-benjamin41902.workers.dev/mcp

Access application

executor-cloudflare

Access team domain

bitter-term-c4e1.cloudflareaccess.com

Host checkout

/Users/davis/Developer/executor-pr877/apps/host-cloudflare

Fast path: the checklist

1. In Cloudflare Zero Trust, create or open the self-hosted Access app for executor-cloudflare.davis-benjamin41902.workers.dev.
2. Add an Allow policy for the intended email address or domain.
3. Copy the Access application’s Application Audience (AUD) Tag.
4. Set ACCESS_TEAM_DOMAIN, ACCESS_AUD, and ADMIN_EMAILS in the Worker config, then redeploy.
5. Edit the Access app and enable Advanced settings → Managed OAuth.
6. Within Managed OAuth, enable Allow localhost clients and Allow loopback clients.
7. Verify that Cloudflare advertises both cloudflared and oauth.
8. Register Codex with both --url and --oauth-resource, using the same MCP URL for each.
9. Complete browser login, then verify the MCP server in Codex.

1. Create the Cloudflare Access application

Open Cloudflare Zero Trust, then navigate to:

Access controls
→ Applications
→ Add an application
→ Self-hosted

Configure the application:

Do not include https:// in the application-domain field.

Add an Access policy for the intended users. A simple personal deployment can use:

Action:  Allow
Include: Emails → your email address

2. Copy the Access application AUD tag

Open the new executor-cloudflare Access application and copy its:

Application Audience (AUD) Tag

The Worker validates Cloudflare Access JWTs itself, so it needs both the team domain and the application audience.

3. Tell the Worker about Cloudflare Access

Open the Cloudflare host checkout:

cd /Users/davis/Developer/executor-pr877/apps/host-cloudflare

Update the vars block in wrangler.jsonc with the real Access values:

"vars": {
  "ACCESS_TEAM_DOMAIN": "bitter-term-c4e1.cloudflareaccess.com",
  "ACCESS_AUD": "<your Access application AUD tag>",
  "ADMIN_EMAILS": "<your email address>"
}

Redeploy the Worker:

bunx wrangler deploy

4. Enable Managed OAuth for non-browser clients

A basic Access application is sufficient for browser login, but it is not sufficient for Codex and other cross-device MCP clients.

Edit the same Access application:

Access controls
→ Applications
→ executor-cloudflare
→ Edit
→ Advanced settings
→ Managed OAuth

Enable all three settings:

• Managed OAuth
• Allow localhost clients
• Allow loopback clients

Worker deployment and Zero Trust configuration are separate control planes. Running wrangler deploy again cannot enable Managed OAuth. A Wrangler login can be authorized to deploy Workers and manage D1/R2 while still lacking permission to edit Access applications.

5. Verify Managed OAuth at the HTTP boundary

Check Cloudflare’s protected-resource metadata:

curl -fsS \
  https://executor-cloudflare.davis-benjamin41902.workers.dev/.well-known/cloudflare-access-protected-resource/mcp

Before enabling Managed OAuth, Cloudflare advertised only:

[
  "cloudflared"
]

After enabling Managed OAuth correctly, it advertises both:

[
  "cloudflared",
  "oauth"
]

Also inspect the unauthenticated MCP response:

curl -i \
  https://executor-cloudflare.davis-benjamin41902.workers.dev/mcp

The post-fix 401 is expected. It protects the endpoint while giving OAuth-capable clients enough metadata to authenticate.

6. Register Executor in Codex with an OAuth resource indicator

Cloudflare Managed OAuth requires the OAuth resource parameter. If the server was previously registered without it, remove the stale Codex entry:

codex mcp remove executor

Re-add the remote MCP server with the exact MCP URL for both flags:

codex mcp add executor \
  --url https://executor-cloudflare.davis-benjamin41902.workers.dev/mcp \
  --oauth-resource https://executor-cloudflare.davis-benjamin41902.workers.dev/mcp

Use the same URL, including /mcp, for --url and --oauth-resource.

If Codex adds the server without opening the browser automatically, run:

codex mcp login executor

OAuth provider returned `invalid_target`: No+resource+parameter+found

7. Verify the Codex connection

Check the registered MCP servers:

codex mcp list

Then launch Codex:

codex

Inside the Codex TUI, run:

/mcp

Executor should appear as an authenticated remote MCP server.

Troubleshooting map

Reusable copy-paste block

For an existing Worker whose Access vars are already correct:

# Cloudflare dashboard:
# Access controls → Applications → executor-cloudflare → Edit
# → Advanced settings → Managed OAuth
# → Enable Allow localhost clients
# → Enable Allow loopback clients
# → Save

curl -fsS \
  https://executor-cloudflare.davis-benjamin41902.workers.dev/.well-known/cloudflare-access-protected-resource/mcp

codex mcp remove executor

codex mcp add executor \
  --url https://executor-cloudflare.davis-benjamin41902.workers.dev/mcp \
  --oauth-resource https://executor-cloudflare.davis-benjamin41902.workers.dev/mcp

codex mcp login executor
codex mcp list

What was non-obvious

1. Cloudflare Access setup is separate from Worker deployment.
2. Cross-device MCP clients need Managed OAuth, not merely a browser Access policy.
3. Codex’s temporary browser callback requires both localhost and loopback allowances.
4. Codex must send an explicit resource value through --oauth-resource.
5. A healthy protected MCP endpoint returns an unauthenticated 401 Bearer challenge after Managed OAuth is enabled; that is success, not an exposure or deployment failure.

Reference

• Cloudflare Managed OAuth documentation
• OpenAI Codex MCP documentation