Plugin install fails with EXDEV on systems where /tmp is tmpfs

Bug description

Plugin installation fails with EXDEV: cross-device link not permitted when /tmp is a tmpfs (RAM-backed) filesystem and ~/.claude/ is on a disk-backed filesystem.

The installer appears to use fs.rename() to move between these paths, which fails across filesystem boundaries.

Error message

Error: Failed to install: EXDEV: cross-device link not permitted, rename
'/home/jack/.claude/plugins/cache/faire' -> '/tmp/claude-plugin-temp-1770502820948'

Root cause

fs.rename() uses the rename(2) syscall, which cannot move files across mount points. On this system:

• ~/.claude/plugins/cache/ → ext4 on /dev/mapper/luks-... (mounted at /)
• /tmp → tmpfs (RAM-backed, separate filesystem)

This is a common Linux setup — many distributions (Arch, Fedora, etc.) mount /tmp as tmpfs by default.

Suggested fix

Replace fs.rename() with a cross-device-safe move, e.g.:

• fs.cp() + fs.rm() (Node 16.7+)
• or fs.rename() with an EXDEV fallback to copy+delete

Alternatively, create temp files on the same filesystem as the destination (e.g., in ~/.claude/plugins/tmp/) instead of using the system /tmp.

Workaround (confirmed)

Setting TMPDIR to a path on the same filesystem works:

export TMPDIR=~/.claude/tmp
mkdir -p ~/.claude/tmp

Environment

• Claude Code: 2.1.37
• OS: Arch Linux, kernel 6.12.53-1-lts
• /tmp: tmpfs
• /home: ext4 on LUKS-encrypted NVMe