[Bug] Interactive input frozen on startup on Windows 11 PowerShell (v2.1.30–2.1.32)

Description

After upgrading from Claude Code 2.1.29 to 2.1.30 (and persisting through 2.1.31 and 2.1.32), the interactive terminal input is frozen/unresponsive after startup on Windows 11 PowerShell.

Claude Code loads normally — the welcome screen, model info, and input prompt all render correctly — but no keyboard input is accepted. The terminal appears completely frozen.

Workaround

Pressing Shift+? (which opens the shortcuts overlay) and then dismissing it restores input. Pressing arrow keys or Escape can also "wake" the input. This suggests the terminal input handler loses focus during the MCP server child-process spawning at startup.

Observed Behavior

• The Windows Terminal tab title changes to npm exec tsx C:/dev/byggesak-mcp/src/index.ts during startup, even though the MCP server is configured as node C:\dev\byggesak-mcp\dist\index.js. This may indicate that child process spawning is interfering with terminal state.
• A SessionStart:startup hook error message is shown (may or may not be related).
• The issue reproduces in any directory, including an empty test folder with no .mcp.json or project hooks — confirming it's a global issue, not project-specific.
• Version 2.1.29 does not have this issue. The regression started in 2.1.30.

Steps to Reproduce

1. Install Claude Code 2.1.30+ on Windows 11
2. Open Windows PowerShell (not WSL)
3. Run claude in any directory
4. Wait for the welcome screen to fully render
5. Try typing — no input is accepted
6. Press Shift+? or arrow keys to restore input

Environment

• Claude Code: 2.1.32
• OS: Windows 11 (build 10.0.26300)
• Terminal: Windows Terminal + Windows PowerShell
• Node.js: v24.13.0
• Install method: npm global
• MCP servers: 7 servers configured (playwright, github, supabase, context7, memory, lovdata, byggesak — mix of stdio and HTTP)
• Plugins: ~27 enabled plugins

Related Issues

• #18109 — Claude Code hangs indefinitely on Windows PowerShell until keyboard input
• #22103 — Claude Code 2.1.27 freezes after first message (regression)
• #12234 — Claude Code freezes intermittently on Windows Terminal

This appears to be a continuation/variant of #18109 where child-process spawning during MCP server initialization causes the terminal input handler to lose focus on Windows.