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Exit node — bypass Cloudflare anti-bot for ChatGPT / Claude / Grok / X

Many Cloudflare-protected services flag traffic from Google datacenter IP ranges as bots and serve a Turnstile / interactive CAPTCHA / 502 challenge instead of the actual page. Apps Script's UrlFetchApp.fetch() exits from those Google datacenter IPs, so for sites like:

  • chatgpt.com / openai.com (Cloudflare anti-bot, often blocks GCP IPs)
  • claude.ai (same)
  • grok.com / x.com (CF-fronted, returns 502 on Google IPs)

…the regular mhrv-rs apps_script-mode path returns errors like Relay error: json: key must be a string at line 2 column 1 or 502 Relay error because Code.gs is wrapping a CF challenge HTML page that the client can't make sense of.

The exit node is a small TypeScript HTTP endpoint deployed on a serverless platform (val.town, Deno Deploy, fly.io, etc.) that sits between Apps Script and the destination. The traffic chain becomes:

Browser ─┐                                                    ┌─→ Destination
         │                                                    │   (chatgpt.com)
         ▼                                                    │
    mhrv-rs                                                   │
       │                                                      │
       │  TLS to Google IP, SNI=www.google.com (DPI cover)    │
       ▼                                                      │
   Apps Script (Google datacenter)                            │
       │                                                      │
       │  UrlFetchApp.fetch(EXIT_NODE_URL)                    │
       ▼                                                      │
    val.town (non-Google IP)                                  │
       │                                                      │
       │  fetch(real_url)                                     │
       └──────────────────────────────────────────────────────┘

The destination sees the val.town IP, not Google datacenter. CF's anti-bot heuristic doesn't fire, and you get the actual page.

Crucially: the user-side leg (Iran ISP → Apps Script) is unchanged. The ISP still only sees TLS to a Google IP — the second hop happens entirely inside Apps Script's outbound, invisible from the user's network. So the DPI evasion property mhrv-rs is built around stays intact.

Setup

  1. Sign up at val.town (free tier is fine — the free tier's outbound bandwidth is enough for personal use).
  2. Create a new HTTP val (TypeScript). On val.town: New → HTTP.
  3. Paste the contents of valtown.ts from this directory.
  4. Set the PSK at the top of the file: 
    const PSK = "<your-strong-secret>";
    Generate a strong secret with openssl rand -hex 32 from a terminal. Don't leave the placeholder in production — the val.town code intentionally fails closed (returns 503 on every request) until you replace the placeholder, so you can't accidentally serve as an open relay.
  5. Save the val. Copy the val's public URL — it looks like https://your-handle-mhrv.web.val.run.
  6. In your mhrv-rs config.json, add an exit_node block: 
    "exit_node": {
  "enabled": true,
  "relay_url": "https://your-handle-mhrv.web.val.run",
  "psk": "<the same PSK you set in step 4>",
  "mode": "selective",
  "hosts": ["chatgpt.com", "claude.ai", "x.com", "grok.com", "openai.com"]
}
  7. Restart mhrv-rs (Disconnect + Connect, or kill + restart the binary).
  8. Test — visit chatgpt.com or grok.com from a browser pointed at the mhrv-rs proxy. You should see the actual login page now, not a CF challenge.

A complete example config is at config.exit-node.example.json in the repo root.

How selective vs full mode pick

Mode What it does When to use
selective (default) Only hosts in hosts route via exit node; everything else takes the regular Apps Script path Recommended. The exit-node hop adds ~200-500ms per request, so reserve it for sites that need a non-Google IP.
full Every request routes via exit node Only useful when your entire workload is CF-anti-bot affected, or when the exit node happens to be faster than Apps Script alone for your network path (rare). Burns val.town runtime budget for sites that don't need it.

Failure mode

If the exit node is unreachable, returns a 5xx, or returns a malformed response, mhrv-rs falls back to the regular Apps Script relay automatically. You'll see a warn: exit node failed for ... — falling back to direct Apps Script line in the log. Sites that need the exit node will fail in that case (CF challenge), but other sites work normally — a down exit node doesn't take you fully offline.

Security model

The PSK is the only thing keeping the val.town endpoint from being a public open proxy. Treat it like a password:

  • Don't commit the PSK to source control. The val.town source is private to your account by default; keep it that way.
  • Don't share the PSK publicly. Anyone who has both the URL and the PSK can use your val.town quota as their own proxy.
  • Rotate if you suspect leak. Change the PSK in val.town source, save, then update psk in mhrv-rs config.json and restart.

The val.town script also includes a loop guard (refuses to fetch its own host) and placeholder check (returns 503 if PSK === "CHANGE_ME_TO_A_STRONG_SECRET") so a fresh deploy without setup can't accidentally serve as an open relay.

Alternative platforms

The valtown.ts script is plain TypeScript using web-standard APIs (Request, Response, fetch). It runs on:

  • val.town — easiest, free tier sufficient for personal use
  • Deno Deploy — similar API; deploy with deployctl
  • fly.io — needs a Dockerfile wrapper; gives you a fixed geographic region
  • Cloudflare Workers — won't help (CF Workers exit from CF's own IP space, which CF anti-bot still flags as worker-internal)

For most users, val.town's the right choice. Deno Deploy if you want a non-val.town option for redundancy.

Why not always-on by default

  • Adds 200-500ms per request (extra hop)
  • Burns val.town's free-tier bandwidth budget
  • Offers no benefit for sites that don't have CF anti-bot
  • Setup requires a separate account on a third-party platform

So enabled: false is the default. Users who care about ChatGPT / Claude / Grok specifically opt in; everyone else runs lighter.

Troubleshooting

exit node refused or errored: unauthorized — PSK mismatch. Check that the psk in config.json exactly matches the PSK constant in val.town. Whitespace and quoting matter.

exit node refused or errored: exit_node misconfigured: PSK is still the placeholder — you forgot to replace CHANGE_ME_TO_A_STRONG_SECRET in val.town. Edit + save the val.

exit node failed for ...: connection refused — the val.town URL is wrong or the val isn't deployed. Verify by hitting the URL directly from a browser — it should return {"e":"method_not_allowed"} (val expects POST).

exit node failed for ...: timeout — val.town outbound is slow or the destination is slow. Try a different val.town deployment region, or accept the latency trade-off.

Site still shows CF challenge after enabling exit node — CF is flagging val.town's IP too. Some CF customers explicitly blocklist val.town. Workarounds: try Deno Deploy instead, or add the site to passthrough_hosts (bypasses MITM entirely; uses your real ISP IP).

See also