[BUG] /compact fails with 400 when session history contains "advisor" server_tool_use blocks

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?

Running /compact fails with a 400 API error when the session history contains
server_tool_use blocks from the advisor tool.

What Should Happen?

Compaction should strip server_tool_use blocks from the history before sending it to
the compaction API — the same way #26188 fixed the PDF crash by stripping document blocks.
The fix belongs on the Claude Code side, not the user side, since these blocks are written
automatically and there's no way to avoid them.

More importantly: /compact is the only escape hatch when the context limit is hit.
If it throws a 400 and dies, the session is dead. There's no recovery path other than
/clear and losing everything. That's the real problem here.

Error Messages/Logs

Error: Error during compaction: Error: API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.19.content.2.server_tool_use.name: Input should be
      'web_search', 'web_fetch', 'code_execution', 'bash_code_execution', 'text_editor_code_execution', 'tool_search_tool_regex',
     'tool_search_tool_bm25'"},"request_id":""}

Steps to Reproduce

1. Add a rule to the system prompt instructing Claude to call advisor before substantive work
2. Start a session and let Claude invoke advisor at least once (e.g. before a code change)
3. Run /compact or wait for auto-compact to trigger
4. 400 error occurs

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.84

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

_No response_