[Bug] Anthropic API Error: 403 Cloudflare Challenge Block

Resolved 💬 3 comments Opened Mar 3, 2026 by inakov Closed Mar 7, 2026

Bug Description
API Error: 403 <!DOCTYPE html><html lang="en-US"><head><title>Just a moment...</title><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=Edge"><meta name="robots"
content="noindex,nofollow"><meta name="viewport"
content="width=device-width,initial-scale=1"><style>*{box-sizing:border-box;margin:0;padding:0}html{line-height:1.15;-webkit-text-size-adjust:100%;color:#313131;font-family:system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica
Neue",Arial,"Noto Sans",sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol","Noto Color Emoji"}body{display:flex;flex-direction:column;height:100vh;min-height:100vh}.main-content{margin:8rem
auto;padding-left:1.5rem;max-width:60rem}@media (width <= 720px){.main-content{margin-top:4rem}}#challenge-error-text{background-image:url("data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSIzMiIgaGVpZ2h0PSIzMiIg
ZmlsbD0ibm9uZSI+PHBhdGggZmlsbD0iI0IyMEYwMyIgZD0iTTE2IDNhMTMgMTMgMCAxIDAgMTMgMTNBMTMuMDE1IDEzLjAxNSAwIDAgMCAxNiAzbTAgMjRhMTEgMTEgMCAxIDEgMTEtMTEgMTEuMDEgMTEuMDEgMCAwIDEtMTEgMTEiLz48cGF0aCBmaWxsPSIjQjIwRjAzIiBkPSJNMTcuMDM4IDE4LjYxNUgxNC44N0wxNC41NjMgOS
41aDIuNzgzem0tMS4wODQgMS40MjdxLjY2IDAgMS4wNTcuMzg4LjQwNy4zODkuNDA3Ljk5NCAwIC41OTYtLjQwNy45ODQtLjM5Ny4zOS0xLjA1Ny4zODktLjY1IDAtMS4wNTYtLjM4OS0uMzk4LS4zODktLjM5OC0uOTg0IDAtLjU5Ny4zOTgtLjk4NS40MDYtLjM5NyAxLjA1Ni0uMzk3Ii8+PC9zdmc+");background-repeat:no-
repeat;background-size:contain;padding-left:34px}</style><meta http-equiv="refresh" content="360"></head><body><div class="main-wrapper" role="main"><div class="main-content"><noscript><div class="h2"><span id="challenge-error-text">Enable JavaScript
and cookies to continue</span></div></noscript></div></div><script>(function(){window._cf_chl_opt = {cvId: '3',cZone: 'api.anthropic.com',cType: 'managed',cRay: '9d69f6c29982d0ef',cH: '6RJbAoPVaRqU6cXtNAPvfLFQ6gE4J144ZSv4ilWBAXk-1772554778-1.2.1.1-O
qTnZw0eET_kD_.7sEXo6yJvYx94xwU5Qyboxg9N6zYe0Tvt3B2Vucws0Q8DXfpK',cUPMDTk:"/v1/messages?beta=true&__cf_chl_tk=gSmm.070Zg1pPQRCj3pbHfryo1R2KDNQs3e.91SB7kY-1772554778-1.0.1.1-Bt8TqDXyJ2NESirUNdRO049EDab7LWKKsvKcMh1N358",cFPWv: 'g',cITimeS:
'1772554778',cTplC:0,cTplV:5,cTplB: '0',fa:"/v1/messages?beta=true&__cf_chl_f_tk=gSmm.070Zg1pPQRCj3pbHfryo1R2KDNQs3e.91SB7kY-1772554778-1.0.1.1-Bt8TqDXyJ2NESirUNdRO049EDab7LWKKsvKcMh1N358",md:
'LzcXcKms71xUMTTeUJM0JwGQU4cCztuW9j29nObiP6Y-1772554778-1.2.1.1-NxH9jJcpinvKZaugeixik1oCxlSu8TNBd0Qoq8cSA6wSj2lREq0MOXlYJEB7YUxg4oSWDUUW7G_bvr3uZ6KbNPmD9gm1cob36.M.ZGqtOZbhoGFaybpDxsn3RT.GbjSK3Udfxn0lm7gQZckSvxoNQdJAcZTQL8lucIVRA.GmiHQ41Ua6cqj4vV326A
_DSI7HSO9oReyxalFZL9E4Rsi6w8n79JniYWhJBXrJtDLp9.lTd2iw8y4lMf4yshp0yIF26O7HD_cJudsCWNgOnUsunzpLmqQY9FlVq2AADjHuDUnf4R5W23FG.VVQyPTAJ0jMI2jpFW9MlyTyGZiEkoIsjjWJxdVxoKjA7iPuKgeKqfrbzDc36jtVUAAgoGM8kyskpduHvVUhqlRZ7HmrVZpQzi6BjTyFTmRhXMMbnHP4gU9KBYCU_OtR
rfVCsLoUgQ_R4rDX4WrFPf2tpTGZBUf7nkBaVDHILgZnp1516QPUbuT826YXJMmz7Srvl5GC5KLuUPxPN3xXS7QKfwL1XYk7PV4Y95ZKp2Gdq1XzonZh7AAH04XtPqch23O52HlOs4aqCyKc2o5g1YxR3ukMuRz.ibO0rO.0TBHXeeBzDi0ijhCeNgI.qa0COhXLbUhn3bnaIoly8QW4bTp55XzCQ7SbOJSYOvWNqb285pjzFkXlea2QNb
BfRiWADSuVQL2C19xM9OVBb3bd4zXMUagAIpzBcmwOXbyGK5WZiGyqB7qRMKLfWA91d9YZtSaNsiUhYHyKGXgjkFK9XUqVJbzpEmAjaMiZKBE4T_NuF7eIkhT5EboO89uYBwqhnG1Ed35K9ipu',mdrd: '',};var a = document.createElement('script');a.src =
'/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=9d69f6c29982d0ef';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,"/v1/messages?beta=true&__cf_chl_rt_tk=gSmm.070Zg1pPQRCj3pbHfryo1R2KDNQs3e.91SB7kY-1772554778-1.0.1.1-Bt8TqDXyJ2NESirUNdRO049EDab7LWKKsvKcMh1N358"+ window._cf_chl_opt.cOgUHash);a.onload =
function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(a);}());</script></body></html>

Environment Info

Platform: darwin
Terminal: ghostty
Version: 2.1.63
Feedback ID: 46fddb0e-6835-4c91-819c-2e7d14e6e6b9

Errors

[{"error":"Error\n    at YM (/$bunfs/root/claude:92:1144)\n    at <anonymous> (/$bunfs/root/claude:93:10067)\n    at emit (node:events:92:22)\n    at endReadableNT (internal:streams/readable:861:50)\n    at processTicksAndRejections (native:7:39)\n    at request (/$bunfs/root/claude:95:2149)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-03-03T16:17:59.461Z"},{"error":"Error\n    at YM (/$bunfs/root/claude:92:1144)\n    at <anonymous> (/$bunfs/root/claude:93:10067)\n    at emit (node:events:92:22)\n    at endReadableNT (internal:streams/readable:861:50)\n    at processTicksAndRejections (native:7:39)\n    at request (/$bunfs/root/claude:95:2149)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-03-03T16:17:59.462Z"},{"error":"Error\n    at YM (/$bunfs/root/claude:92:1144)\n    at <anonymous> (/$bunfs/root/claude:93:10067)\n…

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