// This issue is intentionally created as epic so you can create bugs as needed, but feel free to move away from epic.

To be able to rebase Firefox ESR and Thunderbird ESR to the latest upstream version 153 that is planned for summer we have to have the packages that provide Rust ready in the required version, so they can be used to build the Firefox and Thunderbird packages on the following releases:

• 7.9
• 8.4.0, 8.6.0, 8.8.0, 8.10.0
• 9.2.0, 9.4.0, 9.6.0, 9.8.0, 9.9.0
• 10.0, 10.2, 10.3

Currently the estimated required version of Rust for Firefox 153 is not known, but for 150 - 152 it should be 1.94+ (according to https://firefox-source-docs.mozilla.org/writing-rust-code/update-policy.html#schedule) or newer, but for the latest information please see DESKTOP-3289. We might not need the newest release, but that depends on the minimum supported Rust version for Firefox 153 which is also not yet available.

If you have more information about the required version from your upstream, please let us know in the issue as well.

Please keep in mind that we will need the Rust available on the following platforms as we build Firefox and Thunderbird on these arches and ship it to customers:

• RHEL 7: s390x, ppc64 ppc64le, x86_64 (only Firefox in RHEL 7 ELS)
• RHEL 8: aarch64, ppc64le, s390x, x86_64
• RHEL 9: aarch64, ppc64le, s390x, x86_64
• RHEL 10: aarch64, ppc64le, s390x, x86_64

Your packages will need to be available in all the brew targets (in a format of "rhel-7.9-z-firefox-esr-153-stack-candidate", rhel-8.4.0-z-firefox-esr-153-stack-candidate, ..) for all RHEL releases that are mentioned above (see the linked RHELBLD tickets for more information). Please open a RHELBLD ticket to request the packages to be tagged there. It's enough to tag packages only into Firefox specific targets as the Thunderbird ones inherit from Firefox ones.

We would also like to track the scope of the Firefox/Thunderbird ESR rebase so we would like to ask you to use the "mozilla-esr-153" label in any JIRA tickets that will be related to this request.

The deadline is June 16, 2026 so we can start to build the packages once Mozilla provides us tarballs. For more information about the rebase schedule see RHELBU-3331.