Starting two VMs can cause failure when VMPal Tools update #97

Description

When two macOS VMs start at the same moment right after a VMPal update that brings new VMPal Tools, one of them can fail to make the shared VMPal Tools folder (~/Library/Application Support/VMPal/VMPal Tools/macOS). Its log says “VMPal Tools” couldn't be copied to “macOS” because an item with the same name already exists. Most likely the other VM's process had just copied the new Install VMPal Tools.app there. VMPal still asks that VM's guest to install the new VMPal Tools, but nothing happens: the guest stays on the old version.

Restarting the VM doesn't help: its VMPalMachine process keeps running across the restart and doesn't try to make the folder again. Only after that process was ended (kill, with the VM shut down) and the VM started again did the update go through, within 8 seconds.

Seen twice, on two Macs, each time when two VMs' processes started within a millisecond of each other at the first start after a VMPal update with new VMPal Tools. Never at other starts, although VMs are often started two at a time here.

Steps to Reproduce

1. Update VMPal to a version with new VMPal Tools (here 0.101 → 0.103, Tools 0.40 → 0.41), with two shut-down macOS VMs that have the old Tools.
2. Before any VM starts, start both at the same time from the command line, e.g. vmpal start "macOS 15" --wait & vmpal start "macOS 26" --wait & wait (a script started them from two threads).
3. Wait for VMPal Tools to update in both VMs.
4. Shut the failed VM down and start it again: still no update.

Current Behavior

• macOS 15 updated to VMPal Tools 0.41 within 2 seconds of connecting.
• macOS 26 logged "The VMPal Tools folder couldn't be made: “VMPal Tools” couldn’t be copied to “macOS” because an item with the same name already exists." 17 ms after its process started (the other VM's process started 1 ms before it). It then logged "VMPal Tools: asked to install VMPal Tools 0.41", but stayed on 0.40 for 10 minutes until it was shut down.
• After two more shut downs and starts by the same VMPalMachine process (pid 52612), VMPal Tools 0.40 connected each time, with no new install attempt.
• After ending that process, the next start (new process 53642) installed 0.41 at once.
• The shared folder afterwards: .version says 0.41, and Install VMPal Tools.app is 0.103's, copied in at 12:04:41.

The same happened on another Mac on 2026-10-15 (MacBook Pro, M5 Pro), with two clones started together by a script at the first start after an update to Tools 0.40: the macOS 15 clone got the error and stayed on 0.39, while the macOS 26 clone, started in the same millisecond, updated.

Nothing showed in VMPal's UI: the VMs were started from the CLI.

Expected Behavior

Both VMs get the new VMPal Tools. If two VMs refresh the shared VMPal Tools folder at once, one waits for the other or uses its result. If making the folder fails, VMPal tries again at the next start or the next install request, rather than only after its VMPalMachine process is restarted.

Environment

• App version: VMPal 0.103 (103)
• Mac: MacBook Air, M5, 32 GB (Mac17,3)
• macOS version: macOS 27.0.1 (26A434)
• VM's OS: macOS 26.6.2 (25G83), the one that failed; started together with macOS 15.6.1 (24G90)

Log

~/Library/Logs/VMPal/macOS 26.log (the VM that failed, 2026-10-27):

2026-10-27 12:04:41.964 VMPalMachine[52612:9937550] The second network card is on the local network, frames up to 1514 bytes
2026-10-27 12:04:41.981 VMPalMachine[52612:9937550] The VMPal Tools folder couldn't be made: “VMPal Tools” couldn’t be copied to “macOS” because an item with the same name already exists.
2026-10-27 12:05:03.618 VMPalMachine[52612:9937550] VMPal Tools 0.40 connected: macOS 26.6.2 (25G83)
2026-10-27 12:05:04.619 VMPalMachine[52612:9937550] VMPal Tools: asked to install VMPal Tools 0.41
2026-10-27 12:15:45.202 VMPalMachine[52612:9937550] Shut Down: an agent on this Mac asked, and VMPal Tools shut the system down
2026-10-27 12:47:17.502 VMPalMachine[52612:9937550] VMPal Tools 0.40 connected: macOS 26.6.2 (25G83)
2026-10-27 12:48:51.174 VMPalMachine[52612:9937550] Shut Down: an agent on this Mac asked, and VMPal Tools shut the system down
2026-10-27 12:49:13.457 VMPalMachine[52612:9937550] VMPal Tools 0.40 connected: macOS 26.6.2 (25G83)
2026-10-27 12:54:05.867 VMPalMachine[52612:9937550] Shut Down: an agent on this Mac asked, and VMPal Tools shut the system down
   (process 52612 ended here with kill -TERM, VM shut down)
2026-10-27 12:54:07.384 VMPalMachine[53642:9966825] The second network card is on the local network, frames up to 1514 bytes
2026-10-27 12:54:27.807 VMPalMachine[53642:9966825] VMPal Tools 0.40 connected: macOS 26.6.2 (25G83)
2026-10-27 12:54:28.834 VMPalMachine[53642:9966825] VMPal Tools: asked to install VMPal Tools 0.41
2026-10-27 12:54:36.230 VMPalMachine[53642:9966825] VMPal Tools 0.41 connected: macOS 26.6.2 (25G83)

~/Library/Logs/VMPal/macOS 15.log (started 1 ms earlier, updated fine):

2026-10-27 12:04:41.965 VMPalMachine[52614:9937590] The second network card is on the local network, frames up to 1514 bytes
2026-10-27 12:04:57.034 VMPalMachine[52614:9937590] VMPal Tools 0.40 connected: macOS 15.6.1 (24G90)
2026-10-27 12:04:58.034 VMPalMachine[52614:9937590] VMPal Tools: asked to install VMPal Tools 0.41
2026-10-27 12:04:59.716 VMPalMachine[52614:9937590] VMPal Tools 0.41 connected: macOS 15.6.1 (24G90)

The other Mac, 2026-10-15: macOS 15 e2e 15.log (failed; no 0.40 followed until the clone was deleted) and macOS 26 e2e 26.log (updated):

2026-10-15 11:50:53.286 VMPalMachine[8087:181613] The second network card is on the local network, frames up to 1514 bytes
2026-10-15 11:50:53.378 VMPalMachine[8087:181613] The VMPal Tools folder couldn't be made: “VMPal Tools” couldn’t be copied to “macOS” because an item with the same name already exists.
2026-10-15 11:51:04.786 VMPalMachine[8087:181613] VMPal Tools 0.39 connected: macOS 15.6.1 (24G90)
2026-10-15 11:51:05.807 VMPalMachine[8087:181613] VMPal Tools: asked to install VMPal Tools 0.40

2026-10-15 11:50:53.286 VMPalMachine[8086:181607] The second network card is on the local network, frames up to 1514 bytes
2026-10-15 11:51:17.113 VMPalMachine[8086:181607] VMPal Tools 0.39 connected: macOS 26.6.2 (25G83)
2026-10-15 11:51:18.115 VMPalMachine[8086:181607] VMPal Tools: asked to install VMPal Tools 0.40
2026-10-15 11:51:21.655 VMPalMachine[8086:181607] VMPal Tools 0.40 connected: macOS 26.6.2 (25G83)