[BUG] Claude Code hangs on startup on Windows Server 2022 (no output, ~1 CPU core per process), even with clean CLAUDE_CONFIG_DIR

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?

Claude Code hangs on startup on Windows Server 2022: no output at all, each
claude.exe process uses ~1 full CPU core with ~19 MB RAM (looks like a busy
loop). Happens in Claude Desktop sessions in any folder (incl. an empty one)
and when running claude.exe directly with a clean CLAUDE_CONFIG_DIR.
--version works instantly. Processes accumulate (7 at once observed).
Claude.ai chat in the same app works fine.

What Should Happen?

claude -p "hello" should return a response; Desktop sessions should respond.

Error Messages/Logs

claude.exe -p "hello" --debug -> no output at all, hangs indefinitely
C:\temp\cc-clean after the hang: [empty / contains: ...]

Claude Desktop main.log:
[CCD] Session ... timed out after 991s of inactivity (hadFirstResponse=false, seconds_since_stderr=never, probe_result=no_answer)
[CCD] query.interrupt() did not resolve within 1500ms ... SDK abort not honoured pre-first-byte
[CCD] sendMessage on uninitialized session ... (CLI died before init)
Failed to get commands from temporary query: Temporary query did not answer within 90000ms

Steps to Reproduce

1. Windows Server 2022 (21H2, build 20348.5622), multi-user RDP terminal server (2 users logged in)
2. In cmd: claude.exe --version -> "2.1.295 (Claude Code)" instantly
3. set CLAUDE_CONFIG_DIR=C:\temp\cc-clean
4. cd C:\temp\cc-clean (empty folder)
5. claude.exe -p "hello" -> hangs indefinitely, no output, ~1 CPU core busy
6. Same result with --debug

Ruled out: project config (empty folder), user config/state (clean CLAUDE_CONFIG_DIR),
network (hangs before any request), antivirus/VPN/proxy (none), MCP servers and hooks (none).

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.295 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

• Claude Desktop 2.31226.1, MSIX package (C:\Program Files\WindowsApps\...), downloaded from claude.ai, not Microsoft Store
• 16 GB RAM, x64
• Happy to run a Process Monitor trace or other diagnostics if useful