Qubes OS 4.3.0-rc2 is available for testing

[Andrew David Wong]

Dear Qubes Community,

We're pleased to announce that the second release candidate (RC) for Qubes OS 4.3.0 is now available for testing. This minor release includes many new features and improvements over Qubes OS 4.2.

## What's new in Qubes 4.3?

- Dom0 upgraded to Fedora 41 ([#9402](https://github.com/QubesOS/qubes-issues/issues/9402)).
- Xen upgraded to version 4.19 ([#9420](https://github.com/QubesOS/qubes-issues/issues/9420)).
- Default Fedora template upgraded to Fedora 42 (versions older than release 41 not supported).
- Default Debian template upgraded to Debian 13 (versions older than release 12 not supported).
- Default Whonix templates upgraded to Whonix 17.4.3 (versions older than release 17 not supported).
- Preloaded disposables ([#1512](https://github.com/QubesOS/qubes-issues/issues/1512))
- Device "self-identity oriented" assignment (a.k.a. New Devices API) ([#9325](https://github.com/QubesOS/qubes-issues/issues/9325))
- Qubes Windows Tools reintroduced with improved features ([#1861](https://github.com/QubesOS/qubes-issues/issues/1861)).

These are just a few highlights from the many changes included in this release. For a more comprehensive list of changes, see the [Qubes OS 4.3 release notes](https://doc.qubes-os.org/en/latest/developer/releases/4_3/release-notes.html).

## When is the stable release?

That depends on the number of bugs discovered in this RC and their severity. As explained in our [release schedule](https://doc.qubes-os.org/en/latest/developer/releases/version-scheme.html#release-schedule) documentation, our usual process after issuing a new RC is to collect bug reports, triage the bugs, and fix them. If warranted, we then issue a new RC that includes the fixes and repeat the process. We continue this iterative procedure until we're left with an RC that's good enough to be declared the stable release. No one can predict, at the outset, how many iterations will be required (and hence how many RCs will be needed before a stable release), but we tend to get a clearer picture of this as testing progresses.

At this time, we expect that there will likely be a third release candidate.

## How to test Qubes 4.3.0-rc2

Thanks to those who tested 4.3.0-rc1 and [reported bugs they encountered](https://doc.qubes-os.org/en/latest/introduction/issue-tracking.html), 4.3.0-rc2 now includes fixes for several bugs that were present in the first release candidate!

If you'd like to help us [test](https://doc.qubes-os.org/en/latest/user/downloading-installing-upgrading/testing.html) this release candidate, you can [upgrade to Qubes 4.3.0-rc2](https://doc.qubes-os.org/en/latest/user/downloading-installing-upgrading/upgrade/4_3.html) with either a clean installation or an in-place upgrade from Qubes 4.2. (Note for in-place upgrade testers: `qubes-dist-upgrade` now requires `--releasever=4.3` and may require `--enable-current-testing` for testing releases like this RC.) As always, we strongly recommend [making a full backup](https://doc.qubes-os.org/en/latest/user/how-to-guides/how-to-back-up-restore-and-migrate.html) beforehand and [updating Qubes OS](https://doc.qubes-os.org/en/latest/user/how-to-guides/how-to-update.html) immediately afterward in order to apply all available bug fixes.

Existing 4.3.0-rc1 users can [update normally](https://doc.qubes-os.org/en/latest/user/how-to-guides/how-to-update.html) with [`current-testing` enabled](https://doc.qubes-os.org/en/latest/user/downloading-installing-upgrading/testing.html#updates) in order to make their systems effectively equivalent to 4.3.0-rc2.

Please help us improve the eventual stable release by [reporting any bugs you encounter](https://doc.qubes-os.org/en/latest/introduction/issue-tracking.html). If you're an experienced user, we encourage you to [join the testing team](https://forum.qubes-os.org/t/joining-the-testing-team/5190).

## Known issues in Qubes OS 4.3.0-rc2

It is possible that templates restored in 4.3.0-rc2 from a pre-4.3 backup may continue to target their original Qubes OS release repos. This does not affect fresh templates on a clean 4.3.0-rc2 installation. For more information, see issue [#8701](https://github.com/QubesOS/qubes-issues/issues/8701).

[View the full list of known bugs affecting Qubes 4.3](https://github.com/QubesOS/qubes-issues/issues?q=is%3Aissue%20type%3ABug%20label%3Aaffects-4.3%20-label%3A%22R%3A%20cannot%20reproduce%22%20-label%3A%22R%3A%20declined%22%20-label%3A%22R%3A%20duplicate%22%20-label%3A%22R%3A%20not%20applicable%22%20-label%3A%22R%3A%20self-closed%22%20-label%3A%22R%3A%20upstream%20issue%22) in our [issue tracker](https://doc.qubes-os.org/en/latest/introduction/issue-tracking.html).

## What's a release candidate?

A release candidate (RC) is a software build that has the potential to become a stable release, unless significant bugs are discovered in testing. RCs are intended for more advanced (or adventurous!) users who are comfortable testing early versions of software that are potentially buggier than stable releases. You can read more about Qubes OS [supported releases](https://doc.qubes-os.org/en/latest/user/downloading-installing-upgrading/supported-releases.html) and the [version scheme](https://doc.qubes-os.org/en/latest/developer/releases/version-scheme.html) in our documentation.

## What's a minor release?

The Qubes OS Project uses the [semantic versioning](https://semver.org/) standard. Version numbers are written as `[major].[minor].[patch]`. Hence, releases that increment the second value are known as "minor releases." Minor releases generally include new features, improvements, and bug fixes that are backward-compatible with earlier versions of the same major release. See our [supported releases](https://doc.qubes-os.org/en/latest/user/downloading-installing-upgrading/supported-releases.html) for a comprehensive list of major and minor releases and our [version scheme](https://doc.qubes-os.org/en/latest/developer/releases/version-scheme.html) documentation for more information about how Qubes OS releases are versioned.


This announcement is also available on the Qubes website:
https://www.qubes-os.org/news/2025/09/19/qubes-os-4-3-0-rc2-available-for-testing/