The Hermes-managed Node tree at %HERMES_HOME%\node is destructively
rewritten while the desktop app's Node processes execute from it:
the Node-26 heal did shutil.rmtree + move, the EBADENGINE repair ran
npm install --global --prefix into the tree, and install.ps1's
Test-Node did Remove-Item + Move-Item. Windows rejects those writes
with PermissionError: [WinError 5] on npm.cmd.
- _heal_managed_node_windows: stage the fully-downloaded tree in a
sibling node.new-* dir, then rename-swap (live tree -> node.old-*,
staged -> node). The live tree is never deleted before its
replacement is ready, so an interrupted heal cannot gut it; a
refused rename is the OS-level in-use signal and defers (returns
None) instead of forcing the write.
- heal_hermes_managed_node: an in-use deferral does not record the
once-per-process attempt, so the heal retries once the tree is free.
- managed_node_tree_in_use: cheap psutil pre-check (Windows only) that
avoids pointless 30-50MB re-downloads in long-lived processes.
- upgrade_managed_npm: defer the in-place npm self-upgrade while the
tree is in use, with a notice.
- install.ps1: Test-ManagedNodeInUse guard around Update-ManagedNpm and
the Test-Node install branch, which now rename-swaps instead of
delete-then-move.
An in-use-but-outdated tree keeps serving the old runnable Node (old
Node beats no Node), and every npm resolution re-evaluates the heal, so
the upgrade applies automatically on the next update with the app
closed.
David Metcalfe
e4d0e4c3d8