I’m having a critical issue with Claude Code on Windows where the Bash tool is completely broken across all projects and sessions. This started happening today (Feb 25, 2026) and I’ve tried multiple fixes with no success. Every bash command fails with: EINVAL: invalid argument, open ‘C:\Users\username\AppData\Local\Temp\claude\C–Users-43664\tasks{random}.output’ This happens regardless of which command I run (even simple echo or pwd). The error occurs before the bash command even executes. Environment:
- Windows 11 (MINGW64_NT-10.0-26100)
- Git Bash (MSYS2)
- Claude Code (latest version as of Feb 25) What I’ve Tried: ✗ Restarting Claude Code ✗ Running from a project folder instead of home directory ✗ Updated Claude Code to latest version ✗ Set MSYS_NO_PATHCONV=1 environment variable before launching Claude ✗ Checked Windows Defender protection history (nothing blocked) ✗ Manually created the temp directory ✗ Used alternative tools (Glob, Read, Write) - these work fine Key Details:
- The temp directory exists and is writable (confirmed by other tools)
- This affects ALL sessions - even previously working projects
- Error originates from openSync in the Bun runtime (claude.exe)
- Debug logs show: “Session environment not yet supported on Windows” followed by the EINVAL error Has anyone experienced this? Would appreciate any suggestions! submitted by /u/ReporterCalm6238
Originally posted by u/ReporterCalm6238 on r/ClaudeCode
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