[BUG] OAuth login hangs when Cloudflare challenges CLI requests

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Environment:

Windows (native, not WSL)
Claude Code version: 2.0.76
Location: France (Orange/Wanadoo ISP)

Description:
Running /login hangs indefinitely. No browser window opens, no URL is printed to the terminal.
Diagnosis:

Root cause:
Cloudflare blocks the CLI's requests because they cannot execute JavaScript challenges. Browser requests pass because they can.

What Should Happen?

The OAuth flow should either bypass the challenge (allowlisted user agent?) or gracefully fall back to printing a URL for manual browser authentication.

Error Messages/Logs

PS C:\Users\horas>    curl https://claude.ai
curl :
<div class="h2"><span id="challenge-error-text">Enable JavaScript and cookies to continue</span></div>
(function(){window._cf_chl_opt = {cvId: '3',cZone: 'claude.ai',cType: 'managed',cRay: '9baf90f478450f1e',cH: 'EJgXgRxY4
si8zocBLqvvKf8FePmwwqq6Uy1ym4xoKWQ-1767915902-1.2.1.1-2zDFOSgqPc2xC0r8I_wgjXRxJkclrLSyMA6BwKcpXNT52ee0wfPaiC4F_ftzgXYa'
,cUPMDTk:"\/?__cf_chl_tk=Nm1YW_F0flA2XCeTLowWmWo84J4up6EgJeypim0dYdg-1767915902-1.0.1.1-sU88WRe3dsW3NWT9ZeV5vwMi4ZvB9YP
QxJgIfA5S4lA",cFPWv: 'g',cITimeS: '1767915902',cTplC:0,cTplV:5,cTplB: '0',fa:"\/?__cf_chl_f_tk=Nm1YW_F0flA2XCeTLowWmWo8
4J4up6EgJeypim0dYdg-1767915902-1.0.1.1-sU88WRe3dsW3NWT9ZeV5vwMi4ZvB9YPQxJgIfA5S4lA",md: 'E_4rnmVqJvLi0.C59zK9b76tgreKjy
AFoI4XLVRcRK0-1767915902-1.2.1.1-D6jVc5fc8aPxu0IOQ0_BEb5tAeIe.guix9W2DmN_un_h12Of1iX9P.Pz7B6ZT_74ypwI9ELBukvyCZj8WswVgd
LG_9pU0tbJVza57lG7gRIyvqdC5Alvi8pr1cn8uwzm3fjVKnnP.1djVzUMjvXKQoAieDqvQNMSs4.la6OlF6cxOJYwjEktG9vhCcUlRaGBwOKK4PBum5lHe
Xs1MnYOloxBZLBDTBARYPqJAYmymWDnOyuHdQYbkD67WqzNgukqucPv59h9_gbBEY_Z2FbCBXINyYSZwdZy04d5wYwi1jpxiYBUHf4eLDmTkChlCUu1ZzkW
bu3MNcvZjT7asWemVnRa2zXehPexnF.OPy9CpbbMHpAol7E7Uec3DbhwIp75jFAzdvGiER496o1lbzKB56TnazyqnH2bj5vIC1.FFcEqemJBvzv0cFGVCG3
VcjIA7sHu5Io4i_.WpaYO0IHKClGWyuJTuiTv_d.BcCb1WJcHaoa.eHfTvqwp.HMPGYPIj6pubqeZqVQm7ZB7eedt7jFGb5GVfVc51W5k_cW5s_JSMMOsyD
Rm2X9nv9wS337i1cWaPZ3LW8BSahfFj14c8VV7Ce9ohRvW3KsCaSS3aVJJlWJAKisCgFZ1qOLlK2hbv5IN4PN_OUQI.gQjJXpdHFZrpCAxVrqAEuV6vog0v
eRuozQ.cHY.CDnd52OZkGrM3ChNxbjBr2k4H9MRmMWTsayPkno8vx11PJLbiSFzXgOuM5ZNp_rUvmbbesYgb5z8eoHIDxI.968a0.L5HVgXOKUbudSAxhQO
rMatRkYafEEux.emFPcwBNsQvy83dBx9HFH3Ag1c4iPo2Ns_3E2OkK1F5Ul71Ccd3W_tbhA8F9anEg_9sPBkOxJK9pg9x_0x7_zrGIiPdKpBx4d6FtzCsIP
Odo590jAayJYAEJLPs4GFyEVoS8TLSaLwgZukNRd5D_jfQLsJVOQL6O02bOGtI8aetIF8qa4Pz2dnVolXuK9tV18r0iB0bqkrBICoUOFkBGUOuN9MfHsYJm
2n1QNIjFPeLdpzdi7QHHHYKuN4A_0',mdrd: 'OIdQKbcKV6Z6AxKIxibu5Ef7w.nVF3H.MXY0vsM9ADo-1767915902-1.2.1.1-B.x8jfEmKaDmfZY4Rk
2EE7Yopfgt22yAokU0ZMYmX6otMDa4A8sqx9BhVc0jlombBvBEDFjORuOOuhdgWdhY.cZjujj1a66Y2kdg_1ZYOjT1nCAa4SH5J4UhNp0s04VhVh48vAiUA
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QrVw8HVfuxSO99uWNhfrU15SsGpaa5HC2KJADSz.ezjxFYnTB_N888n1mE1tgJhjss1bBONJ_kjoP2SWJCX6Kr3s7Ho4Rap61QADnfrYsQWX.HledWd9Zkj
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oiFfHw0odgF3sJ3oX6hyK6KtQ5mE4hAM7KssXHqWXb8e0dMRGq0Kgc1459T7pEAljLxtbOGKfe2IEhOqiNKm9GeA0B2H0ZdxSn3NKOQ.naQB7Nq3ZV4sQbl
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document.createElement('script');a.src =
'/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=9baf90f478450f1e';window._cf_chl_opt.cOgUHash =
location.hash === '' && location.href.indexOf('#') !== -1 ? '#' : location.hash;window._cf_chl_opt.cOgUQuery =
location.search === '' && location.href.slice(0, location.href.length -
window._cf_chl_opt.cOgUHash.length).indexOf('?') !== -1 ? '?' : location.search;if (window.history &&
window.history.replaceState) {var ogU = location.pathname + window._cf_chl_opt.cOgUQuery +
window._cf_chl_opt.cOgUHash;history.replaceState(null, null,"\/?__cf_chl_rt_tk=Nm1YW_F0flA2XCeTLowWmWo84J4up6EgJeypim0d
Ydg-1767915902-1.0.1.1-sU88WRe3dsW3NWT9ZeV5vwMi4ZvB9YPQxJgIfA5S4lA"+ window._cf_chl_opt.cOgUHash);a.onload =
function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(a);}());
At line:1 char:4
+    curl https://claude.ai
+    ~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-WebRequest], WebExc
   eption
    + FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeWebRequestCommand

Steps to Reproduce

1. PowerShell curl https://claude.ai from the same machine returns a Cloudflare JavaScript challenge (Enable JavaScript and cookies to continue)
2. Browser access to claude.ai works normally on the same network/IP
3. IP is not flagged on AbuseIPDB
4. Traceroute shows normal routing to Cloudflare

Deleting %USERPROFILE%\.claude\.credentials.json and retrying does not help

1. CLI hangs, /logout followed by /login does not help

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Worked fine 10 hours ago

Claude Code Version

2.0.76 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

<img width="709" height="518" alt="Image" src="https://github.com/user-attachments/assets/d9292c1e-d792-457a-a368-7d14a21b77d2" />