Concurrent Claude Code instances corrupt .claude.json on Windows (JSON Parse error: Unexpected EOF)

Bug Report

Version: v2.1.59
OS: Windows 11 Pro (PowerShell / pwsh)

Description

When running Claude Code in one PowerShell terminal and then opening a second PowerShell terminal to run another Claude Code instance concurrently, the second instance fails with:

C:\Users\satoshi\.claude.json is corrupted: JSON Parse error: Unexpected EOF

Steps to Reproduce

1. Open a PowerShell (pwsh) terminal
2. Run claude (Claude Code starts normally)
3. While the first instance is still running, open a second PowerShell terminal
4. Run claude in the second terminal
5. The second instance throws the JSON parse error

Expected Behavior

Both Claude Code instances should be able to run concurrently without corrupting the shared .claude.json config file. The file access should be properly synchronized (e.g., file locking or atomic writes).

Actual Behavior

The second instance encounters a corrupted .claude.json file, likely due to a race condition where one instance is writing to the file while the other tries to read it simultaneously.

Additional Context

This appears to be a file locking / concurrent access issue on Windows. The .claude.json file is shared across instances and lacks proper synchronization for concurrent read/write operations.