fix(filesystem): handle Windows EPERM on file rename when target is locked#3632
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ctonneslan wants to merge 1 commit intomodelcontextprotocol:mainfrom
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…ocked On Windows, fs.rename() throws EPERM when the target file is locked by another process (e.g., open in VS Code or Notepad). This breaks both write_file and edit_file operations. Added an atomicReplace() helper that falls back to copyFile + unlink on Windows when rename fails with EPERM. This preserves the atomic write semantics on Linux/macOS while working around the Windows file locking limitation. Fixes modelcontextprotocol#3199
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Problem
On Windows,
fs.rename()throwsEPERMwhen the target file is locked by another process (e.g., open in VS Code, Notepad, or any editor). This breaks bothwrite_fileandedit_fileoperations with:This works fine on Linux and macOS where rename atomically replaces the target regardless of read locks.
Fix
Added an
atomicReplace()helper function that:fs.rename()first (preserves atomic semantics on Linux/macOS)EPERM+process.platform === 'win32'), falls back tofs.copyFile()+fs.unlink()of the temp fileApplied to both write locations in
lib.ts:writeFileSecure()(used bywrite_filetool)applyFileEdits()(used byedit_filetool)The fallback is only triggered on Windows and only when the specific
EPERMerror occurs, so behavior on other platforms is unchanged.Fixes #3199