[BUG] WebFetch "Unable to verify domain is safe" error

Environment

• Platform (select one):
• Claude CLI version: 1.0.89 (Claude Code)
• Operating System: macOS (Darwin 24.6.0)
• Terminal: VS Code integrated terminal

Bug Description

WebFetch tool fails to access Microsoft Learn documentation URLs with "Unable to verify if domain is safe to
fetch" error. This appears to be a regression as the functionality worked previously. The issue affects deep URLs
while base domains work correctly.

Steps to Reproduce

1. Open Claude Code in VS Code
2. Use WebFetch tool with command: WebFetch(url: "https://learn.microsoft.com/en-us/semantic-kernel/concepts/plugi

ns/adding-mcp-plugins?pivots=programming-language-python", prompt: "Get documentation content")

1. Observe the error response

Expected Behavior

WebFetch should successfully fetch and process content from Microsoft Learn documentation pages, as it did in
previous versions.

Actual Behavior

Error: Unable to verify if domain learn.microsoft.com is safe to fetch. This may be due to network restrictions or
enterprise security policies blocking claude.ai.
API Error (Request timed out.) · Retrying in 1 seconds… (attempt 1/10)

Full prompt:
read https://learn.microsoft.com/en-us/semantic-kernel/concepts/plugins/adding-mcp-plugins and make sure we are
following this pattern

⏺ I'll read the Microsoft documentation on MCP plugins in Semantic Kernel to ensure we're following the correct
pattern.

⏺ Fetch(https://learn.microsoft.com/en-us/semantic-kernel/concepts/plugins/adding-mcp-plugins)
⎿ Error: Unable to verify if domain learn.microsoft.com is safe to fetch. This may be due to network restrictions
or enterprise security policies blocking claude.ai.

⏺ Let me try a web search instead to find the Microsoft Semantic Kernel MCP plugin documentation.

⏺ Web Search("Microsoft Semantic Kernel MCP plugins adding pattern documentation 2024")
⎿ Did 0 searches in 360ms

Additional Context

Working URLs:

• ✅ https://www.google.com - Works consistently
• ✅ https://learn.microsoft.com (base domain) - Works
• ✅ https://github.com - Works initially but sometimes fails after repeated use

Failing URLs:

• ❌ https://learn.microsoft.com/en-us/semantic-kernel/... (deep URLs with paths)
• ❌ Some GitHub deep URLs after initial usage

Network Verification:

• Local network can access all URLs successfully via curl/browser
• Issue appears to be on Anthropic's infrastructure side, not user network
• Inconsistent behavior suggests rate limiting or domain filtering policies

Impact: This significantly reduces Claude Code effectiveness for searching web for development workflows and
documentation research tasks.