Bug: Claude Code freezes indefinitely on Windows after installing Ponytail

[VingadorMode]

🐛 Bug: Claude Code freezes indefinitely on Windows after installing Ponytail

💻 Environment

• OS: Windows 10 (PowerShell 5.1)
• Node.js: v18+
• Claude Code: Latest (VSCode extension)
• Ponytail: Installed via npm install -g @dietrichgebert/ponytail

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🛑 Symptoms

After installing Ponytail, Claude Code freezes completely when submitting any prompt. The terminal becomes unresponsive — no spinner, no output, no error. Only Ctrl+C recovers the session.

A secondary issue occurs on first launch:

Failed to set model: Unexpected token '', "{ "p"... is not valid JSON

This is caused by a UTF-8 BOM prepended by PowerShell when writing settings.json.

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🔍 Root Cause Analysis

Two distinct issues were identified during investigation:

1. Stdin EOF deadlock (Critical — causes the freeze)

ponytail-mode-tracker.js (the UserPromptSubmit hook) reads stdin using the following pattern:

process.stdin.on('data', chunk => { input += chunk; });
process.stdin.on('end', () => {
  // parse JSON, process command, exit
});

[DietrichGebert]

The freeze is fixed in #477 (reconciled from @Hasnan42 #453). Root cause was the UserPromptSubmit hook: on Windows it runs through a PowerShell if {} wrapper that can swallow the piped prompt JSON, so stdin never reaches node, the 'end' event never fires, and the hook waits on stdin forever, blocking the session. The hook is now non-blocking, with a 1s fallback that exits cleanly if EOF never arrives, so it can not hang the session again. Verified on Windows: the never-closing-stdin case now exits in about a second instead of hanging.

The secondary settings.json BOM error you spotted (Failed to set model ... not valid JSON) is a separate issue, tracked in #375. Thanks for the sharp root-cause writeup.