Fix: Windows Ctrl+C Terminal Corruption Issue

[weegens-aaron]

Fix: Windows Ctrl+C Terminal Corruption Issue

Summary

This PR fixes a critical Windows-specific terminal corruption issue that occurs when users interrupt long-running operations with Ctrl+C. The problem manifested as corrupted terminal display with stuck formatting and unresponsive input, significantly degrading the user experience on Windows systems.

Changes Made

Main.py Changes

• Pre-prompt cleanup: Added Windows-specific terminal state reset before user input prompts to ensure clean state
• Post-cancellation cleanup: Implemented terminal state restoration after task cancellation to prevent corruption
• Platform detection: Used platform.system() == "Windows" to apply fixes only on Windows systems
• Graceful degradation: Wrapped all Windows-specific code in try-catch blocks to prevent crashes on non-Windows systems

Console Spinner Changes

• Comprehensive cleanup: Added multi-step terminal restoration when Rich's Live display stops
• ANSI reset: Reset all ANSI formatting codes for both stdout and stderr
• Line clearing: Clear current line and reposition cursor properly
• Keyboard buffer flush: Clear any stuck keys from the input buffer using Windows-specific msvcrt functions
• Defensive programming: Handle ImportError gracefully for non-Windows Python implementations

Technical Details

Root Cause Analysis

The issue stemmed from two main problems:

1. Rich's Live Display: The Rich library's Live display can leave the Windows terminal in a corrupted state after interruption
2. ANSI state accumulation: Unhandled Ctrl+C interrupts leave ANSI formatting codes active, causing display corruption

Implementation Approach

• Layered cleanup: Applied terminal resets at multiple points (before input, after cancellation, spinner cleanup)
• Minimal invasiveness: Changes only affect Windows systems, with no impact on Unix-like systems
• Fail-safe design: All Windows-specific code wrapped in exception handlers to prevent cascading failures

Design Patterns Used

• Platform-specific implementation: Clean conditional logic for platform detection
• Defensive programming: Comprehensive error handling with silent failure
• Resource cleanup: Proper terminal state management following RAII principles

Files Modified

code_puppy/main.py

• Lines ~478-487: Added pre-prompt terminal reset before user input
• Lines ~650-661: Added post-cancellation terminal reset after task interruption
• Purpose: Prevents terminal corruption during user interaction

code_puppy/messaging/spinner/console_spinner.py

• Lines ~79-106: Added comprehensive Windows terminal cleanup in spinner stop method
• Purpose: Restores terminal state after Rich's Live display operations
• Added import: platform module for platform detection

Testing

Manual Testing Scenarios

1. Ctrl+C interruption: Start a long-running agent task and interrupt with Ctrl+C
2. Multiple interrupts: Rapid Ctrl+C presses during task execution
3. Spinner cancellation: Cancel operations that show the console spinner
4. Cross-platform verification: Confirmed no regression on non-Windows systems

Testing Approach

• Visual verification: Manual testing on Windows 10/11 terminals (cmd, PowerShell, Windows Terminal)
• Graceful degradation: Verified no impact on Unix-like systems
• Error handling: Confirmed no crashes when terminal operations fail

Recommended Testing

• Test on multiple Windows terminal emulators
• Verify behavior with different Python implementations (CPython, PyPy)
• Test with and without Rich console coloring enabled

Breaking Changes

None - This is a purely additive fix that only affects Windows systems and doesn't change any existing interfaces or behavior.

Additional Notes

Windows Terminal Compatibility

• Tested on Windows 10/11 with Command Prompt, PowerShell, and Windows Terminal
• Compatible with both legacy Windows consoles and modern terminal emulators
• No dependency on specific Windows terminal features

Future Considerations

• Consider adding automated tests for Windows terminal state management
• Could be extended to handle other platform-specific terminal issues
• May benefit from additional terminal capability detection

Related Issues

• Fixes terminal corruption during Ctrl+C interruptions
• Resolves display issues with Rich's Live display on Windows
• Improves overall CLI experience for Windows users

Performance Impact

• Negligible: Terminal reset operations are minimal and only executed on Windows
• No overhead: Conditional checks are simple string comparisons
• User benefit: Significantly improves UX by preventing corrupted displays

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Reviewer Checklist:

• Changes only affect Windows systems as intended
• No regression on Unix-like systems
• Error handling is robust and doesn't mask real issues
• Code follows existing project patterns and style
• Documentation is clear and comprehensive