claude update and claude doctor hang indefinitely due to Cloudflare challenge on version check endpoint

Description

claude update and claude doctor hang indefinitely. The root cause is that the version check endpoint (https://claude.ai/api/cli/latest-version) is returning a Cloudflare managed challenge (HTTP 403) instead of the expected JSON response. The CLI's HTTP client cannot solve the JS challenge, so it hangs waiting for a valid response.

Steps to Reproduce

1. Run claude update — hangs at "Checking for updates to latest version..."
2. Run claude doctor — also hangs (it performs the same version check)

Evidence

$ curl -sI https://claude.ai/api/cli/latest-version | head -5
HTTP/2 403
content-type: text/html; charset=UTF-8
cf-mitigated: challenge

The response body is a Cloudflare "Just a moment..." challenge page requiring JavaScript execution.

Meanwhile, the npm registry is reachable and healthy:

$ curl -sI https://registry.npmjs.org/@anthropic-ai/claude-code/latest | head -2
HTTP/2 200
content-type: application/json

Environment

• Claude Code version: 2.1.37
• Platform: macOS (Darwin 24.6.0, arm64)
• Install method: curl -fsSL https://claude.ai/install.sh | bash (standalone binary via ~/.local/share/claude/versions/)

Workarounds

• curl -fsSL https://claude.ai/install.sh | bash works for updating (uses a different code path)
• npm install -g @anthropic-ai/claude-code@latest also works (hits npm registry directly)

Analysis

The Cloudflare WAF rules on claude.ai appear to be blocking the CLI's own programmatic requests to its version check API. The cf-mitigated: challenge header confirms this is a Cloudflare managed challenge, not a server error. The CLI has no mechanism to solve JS challenges or time out gracefully, so it hangs forever.