[BUG] WebSearch tool fails with web_search_20250305 tag not recognized (UPSTREAM_LLM_ERROR)

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?

Web search always fails with the following error, regardless of setup (direct Anthropic API or corporate proxy):

API Error: 400
tools.0: Input tag 'web_search_20250305' found using 'type' does not match any of the expected tags:
'bash_20250124', 'custom', 'memory_20250818', 'text_editor_20250124', 'text_editor_20250429',
'text_editor_20250728', 'tool_search_tool_bm25', 'tool_search_tool_bm25_20251119',
'tool_search_tool_regex', 'tool_search_tool_regex_20251119'
errorCode: UPSTREAM_LLM_ERROR

Environment:

Claude Code version: 2.1.149
OS: macOS
Using both VSCode extension and CLI — same error on both
Tested with direct Anthropic API and SAP Hyperspace LLM Proxy

What Should Happen?

Expected behavior: Web search returns results

Actual behavior: Every web search call fails with UPSTREAM_LLM_ERROR — the web_search_20250305 tool type is not in the list of accepted tags

Error Messages/Logs

Steps to Reproduce

Install Claude Code CLI v2.1.149
Open Claude Code (VSCode extension or CLI)
Ask any question that requires web search (e.g. "Search for best restaurants in Singapore")
Observe the error in the response

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.149

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_