[BUG] WebFetch fails with 403 on npmjs.com URLs

What went wrong?

The WebFetch tool fails with a 403 Forbidden error when attempting to fetch URLs from npmjs.com. This happens because npm blocks AI agents/bots from accessing their package pages.

Example error:

⏺ Fetch(https://www.npmjs.com/package/sablier)
  ⎿  Error: Request failed with status code 403
     ctrl+b to run in background

What should happen?

Either:

1. Claude Code should not attempt to fetch npmjs.com URLs and inform the user that npm blocks AI agents
2. Or a user-agent workaround could be attempted (though this may violate npm's ToS)

Steps to reproduce

1. Start a Claude Code session
2. Ask Claude to fetch information about any npm package
3. Claude attempts to use WebFetch on https://www.npmjs.com/package/<package-name>
4. WebFetch returns 403 error

Environment

• Version: 2.1.6 (Claude Code)
• OS: macOS 26.2 (Tahoe)
• Terminal: WarpTerminal
• Platform: Anthropic API
• Model: Opus 4.5

Is this a regression?

Don't know - this may have always been the case since npm blocks bots.