CRITICAL: Real-time text duplication corruption bug in file handling

CRITICAL BUG: Real-time Text Duplication Corruption in Claude Code File Handling

Summary

Claude Code contains a severe file handling bug that causes real-time text duplication corruption of files in active repositories. This bug corrupts files while the user is working, causing catastrophic data integrity issues.

Environment

• Platform: macOS (Darwin 24.6.0)
• Claude Code Version: Latest (as of 2025-09-07)
• Model: claude-sonnet-4-20250514
• Repository Size: 2000+ files
• File Types Affected: R, YAML, JSON, and other text files

Bug Description

While using Claude Code normally for repository operations, files become corrupted in real-time with text duplication patterns. The corruption happens during:

• File reads/writes
• Repository monitoring
• Normal Claude Code operations

Corruption Pattern

Files show repeated text segments, example:

if (!requireNamespace("cli"  if (!requireNamespace("cli"  if (!requireNamespace("cli"  if (!requireNamespace("cli", quietly = TRUE)) {
    message("Installing cli package..."    message("Installing cli package..."    message("Installing cli package..."    message("Installing cli package...")

Reproduction Steps

1. Open Claude Code in a repository with 1000+ files
2. Use Claude Code for normal file operations (read, edit, analyze)
3. Monitor files during operations
4. Observe real-time corruption with text duplication patterns

Evidence Collected

• Active Corruption: Monitoring showed files being modified during Claude Code operations
• Process Analysis: Multiple Claude processes accessing repository files simultaneously
• Pattern Analysis: Consistent text duplication signature across multiple file types
• Timing: Corruption occurs in seconds/minutes, not hours/days

Impact Assessment

• Severity: CRITICAL - Data corruption/loss
• Scope: Repository-wide file corruption
• Persistence: Corruption continues until Claude Code processes are terminated
• Recovery: Requires git reset/restore operations outside Claude Code

Root Cause Analysis

Investigation points to:

1. Race Condition: Multiple Claude processes competing for file access
2. Buffer Corruption: Text duplication suggests memory/buffer issues
3. File Watching: Excessive file system monitoring causing conflicts
4. Git Index Corruption: Repository metadata being damaged

Workaround

• STOP using Claude Code for affected repositories
• Switch to alternative code editor
• Restore files using git outside Claude Code environment
• Monitor file integrity after each Claude Code session

System Information

Working directory: /Users/rmckinney/Documents/GitHub/climate-finance-research
Platform: darwin
OS Version: Darwin 24.6.0
Repository: Git repository with 2000+ files
File types: R, YAML, JSON, CSV, Markdown

Request

This bug requires immediate attention as it causes catastrophic data corruption during normal Claude Code usage. Users should be warned about this issue until a fix is deployed.

Priority: P0 - Critical data corruption bug
Category: File System / Data Integrity