MSI error 1618: another installation is already in progress

Error 1618: Another installation is already in progress. Complete that installation before proceeding with this install. Windows Installer only runs one install at a time.

What it means

Microsoft lists 1618 as ERROR_INSTALL_ALREADY_RUNNING. Windows Installer sets a lock (a mutex named _MSIExecute) while it processes an install. Two installations cannot run in the same process, so a new attempt returns 1618 while the lock is set.

Winget has its own code for the same idea, 0x8A150102: “Another installation is already in progress. Try again later.”

Why it happens

Another MSI installer or updater is running, maybe in the background.
Windows is installing an update.
A previous install is still finishing.
You started two installs or upgrades at the same time.

How Devpit fixes or avoids it

Update Everything runs one package-manager step at a time, so Devpit does not start two installs by itself. If something else on your PC holds the installer, the winget code 0x8A150102 shows in the summary as another install is running, and you can retry when the other install has ended.

The manual fix

Wait a few minutes. If you started an installer, finish it or close it.
Check Windows Update in Settings for an update that is installing.
Run your command again.
If nothing at all is installing and it still fails, restart Windows and try again before you open other programs.

Sources

Common questions

Why do I get 1618 when nothing seems to be installing?

Windows Installer allows one installation at a time. Something else may be running in the background, for example another installer or an update. Winget-cli users have reported 1618 when an MSI installer was running in the background. Wait a few minutes and retry.

Can I run two winget upgrades at once?

It is safer not to. Two MSI installs cannot run at the same time. Devpit runs its package steps one after another for this reason.