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Werk #19574: Windows agent: drop 32-bit support

Component Checks & agents
Title Windows agent: drop 32-bit support
Date May 20, 2026
Level Major Change
Class New Feature
Compatibility Incompatible - Manual interaction might be required
Checkmk versions & editions
3.0.0b1
Not yet released 		Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT
2.5.0p6 Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT

Checkmk no longer supports 32-bit Windows. Starting with this release, the Windows agent ships as a 64-bit-only build. If you are still running a 32-bit Windows version, you cannot upgrade the agent past this release.

What Changed

  • The Checkmk Agent MSI (check_mk_agent.msi) is now a 64-bit package and refuses to install on 32-bit Windows.
  • The standalone agent executable is now shipped as check_mk_agent.exe (a 64-bit build). The 32-bit standalone is gone, and the separate check_mk_agent-64.exe artefact no longer exists: with only one architecture left, the name no longer carries an architecture suffix. If you previously downloaded check_mk_agent-64.exe, use check_mk_agent.exe instead.
  • cmk-agent-ctl.exe and mk-sql.exe are now native 64-bit binaries. Previously they were built as 32-bit and ran in WOW64 on 64-bit Windows.
  • On a 64-bit Windows host you do not need to do anything: the MSI installs the 64-bit service exactly the way the previous MSI did on 64-bit hosts.

Registry Path Change

The agent's install registry key moves from the 32-bit WOW64 view to the native 64-bit view as a side effect of the MSI now being 64-bit:

  • Before: HKLM\SOFTWARE\WOW6432Node\checkmkservice
  • After: HKLM\SOFTWARE\checkmkservice

The MSI's MajorUpgrade handles this transparently on upgrade — the old key is removed and the new one created at install time. The agent service itself reads the new location.

If you have external tooling (monitoring scripts, inventory collectors, configuration management) that reads the agent's install state directly from the registry, point it at HKLM\SOFTWARE\checkmkservice. Reads via the 64-bit registry view will find it without WOW6432Node in the path.

Migration

If you are running 32-bit Windows hosts, pin them to the last Checkmk release that included 32-bit support, or migrate the host to 64-bit Windows before upgrading the agent.

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