[Bug] Cloudflare HTTP 403 "managed challenge" blocking all API requests from Spectrum ISP IP range

Bug Description
Issue: All HTTPS requests to api.anthropic.com blocked by Cloudflare with HTTP 403 "managed challenge" response. Preventing use of Claude Code for work.

ISP: Spectrum (Charter Communications)
Location: Macedonia, OH
First observed: April 29, 2026, ~13:57 UTC

Confirmed via: curl -v https://api.anthropic.com/v1/messages
Response: HTTP/2 403
Headers: cf-mitigated: challenge, server: cloudflare
Body: Cloudflare JavaScript challenge page

Ruled out:

• No VPN/proxy/DNS filtering
• No system-level proxy (verified via scutil --proxy)
• TLS handshake completes cleanly
• Block occurs at Cloudflare edge before reaching Anthropic servers

Request: Please investigate ray ID and adjust Cloudflare challenge rules for this IP range.

Environment Info

• Platform: darwin
• Terminal: WarpTerminal
• Version: 2.1.123
• Feedback ID: d51cc945-b7b7-4e10-a413-22a1e83e5c12

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/mattelsey/.local/share/claude/versions/2.1.123 (expected in multi-process scenarios)\n    at x86 (/$bunfs/root/src/entrypoints/cli.js:2769:2177)\n    at Jw8 (/$bunfs/root/src/entrypoints/cli.js:2769:1257)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-29T14:23:14.893Z"}]