[BUG] WebFetch Blocks Legitimate Academic/Research Domains

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?

# Bug Report: WebFetch Blocks Legitimate Academic/Research Domains

## Summary
The WebFetch tool incorrectly blocks access to legitimate academic and research domains, preventing users from conducting research tasks.

## Affected Domains (confirmed blocked)

• arxiv.org - Preprint server for scientific papers
• eprint.iacr.org - International Association for Cryptologic Research
• docs.anthropic.com - Anthropic's own documentation
• platform.claude.com - Anthropic's own platform docs

## Error Message
``
Unable to verify if domain [domain] is safe to fetch. This may be due to network restrictions or enterprise security policies blocking claude.ai.
``

## Impact

• Cannot read academic papers for research tasks
• Cannot access Anthropic's own documentation
• Severely limits Claude Code's usefulness for research workflows
• Forces users to manually copy/paste content

## Expected Behavior
WebFetch should allow fetching from well-known academic domains:

• arxiv.org
• eprint.iacr.org
• acm.org
• ieee.org
• researchgate.net
• semanticscholar.org
• github.com
• docs.anthropic.com

## Steps to Reproduce

1. Ask Claude Code to fetch any arxiv paper
2. Use WebFetch tool with url like https://arxiv.org/abs/2502.20589
3. Observe "Unable to verify if domain is safe" error

## Environment

• Claude Code v2.1.12
• Opus 4.5

## Suggested Fix
Add academic/research domains to an allowlist, or implement proper domain verification that doesn't falsely flag legitimate sites.

## Workaround
User must manually fetch content and paste into conversation, defeating the purpose of the tool.

What Should Happen?

..

Error Messages/Logs

Steps to Reproduce

..

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

0.0

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Xterm

Additional Information

_No response_