Plugin install fails with EXDEV when /tmp is on different filesystem

Description

Plugin installation fails with EXDEV: cross-device link not permitted when /tmp is mounted on a different filesystem than ~/.claude/plugins/.

Error Message

Error: Failed to install: EXDEV: cross-device link not permitted, rename
'/home/user/.claude/plugins/cache/<plugin>' -> '/tmp/claude-plugin-temp-1768434350964'

Environment

• OS: openSUSE Tumbleweed (also affects Fedora, Arch, and other systemd-based distros)
• Claude Code version: Latest
• Filesystem layout:
• /home on /dev/nvme0n1p3 (ext4/btrfs)
• /tmp on tmpfs (RAM-based)

Root Cause

The plugin installer uses fs.rename() to move files from the plugin cache to a temp directory in /tmp. The rename() syscall fails with EXDEV when source and destination are on different filesystems.

This is a very common Linux configuration - most systemd-based distributions mount /tmp as tmpfs by default for performance and SSD longevity.

Suggested Fix

When rename() fails with EXDEV, fall back to copy + delete:

async function moveFile(src, dest) {
  try {
    await fs.rename(src, dest);
  } catch (err) {
    if (err.code === 'EXDEV') {
      // Cross-device move: copy then delete
      await fs.cp(src, dest, { recursive: true });
      await fs.rm(src, { recursive: true });
    } else {
      throw err;
    }
  }
}

Alternatively, use a temp directory on the same filesystem as the plugin cache (e.g., ~/.claude/plugins/.tmp/).

Workaround

Users can work around this by setting TMPDIR:

TMPDIR=~/.claude/tmp claude

Reproduction Steps

1. Have a system where /tmp is on tmpfs (default on most modern Linux distros)
2. Run Claude Code
3. Try to install any plugin (e.g., /plugin install <plugin>)
4. Observe the EXDEV error