GHC 9.12.3-rc2 is now available

wz1000 - 2025-11-22

The GHC developers are very pleased to announce the availability of the second release candidate for GHC 9.12.3. Binary distributions, source distributions, and documentation are available at downloads.haskell.org and via GHCup.

GHC 9.12.3 is a bug-fix release fixing several issues of a variety of severities and scopes. A full accounting of these fixes can be found in the release notes. As always, GHC’s release status, including planned future releases, can be found on the GHC Wiki status.

This release candidate will have a two-week testing period. If all goes well the final release will be available the week of 24 November 2025.

The changes from the first release candidate are

• Fix a regression resulting in a panic with empty cases (#26442, #25960).
• Fix for a potential segfault in the bytecode interpreter (#23210).
• Fix for a regression with tabs not being allowed in string gaps (#26415).
• Fix for a crash with the non-moving GC (#26204).
• A rework of how internal symbols used by the code-generator are handled to adapt to changes in the Apple toolchain, enabling this release to bootstrap on macOS 26 Tahoe (#26166).

GHC development is sponsored by:

• Juspay
• QBayLogic
• Channable
• Haskell Foundation
• Serokell
• Well-Typed
• Tweag
• Dotcom-Monitor
• LoadView
• Web Hosting Buddy
• Find My Electric
• Standard Chartered
• UpCloud

We would like to that these sponsors and other anonymous contributors whose on-going financial and in-kind support has facilitated GHC maintenance and release management over the years. Finally, this release would not have been possible without the hundreds of open-source contributors whose work comprise this release.

As always, do give this release a try and open a ticket if you see anything amiss.