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October 2025

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GHC 9.12.3 status update
by Zubin Duggal 28 Oct '25

28 Oct '25

Hi all, I'm currently working on the final set of backports for GHC 9.12.3-rc2. This has been delayed due to #26166 making bootstrapping GHC impossible on the new macOS release. I am currently in the process of backporting the fix for this ticket (among a few other patches) to GHC 9.12. I expect to have rc2 out in the next few days, by the end of this week. Cheers, Zubin. #26166: https://gitlab.haskell.org/ghc/ghc/-/issues/26166

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GHC 9.14.1-alpha3 is now available
by Ben Gamari 09 Oct '25

09 Oct '25

The GHC developers are very pleased to announce the availability of the third alpha release of GHC 9.14.1. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org] GHC 9.14 will bring a number of new features and improvements, including: * Significant improvements in specialisation: * The `SPECIALISE` pragma now allows use of type application syntax * The `SPECIALISE` pragma can be used to specialise for expression arguments as well as type arguments. * Specialisation is now considerably more reliable in the presence of `newtype`s * Significant improvements GHCi including: * Correctness and performance improvements in the bytecode interpreter * Features in the GHCi debugger * Support for multiple home units in GHCi * Implementation of the [Explicit Level Imports proposal][levels] * `RequiredTypeArgments` can now be used in more contexts * SSE/AVX2 support in the x86 native code generator backend * A major update of the Windows toolchain * ... and many more A full accounting of changes can be found in the [release notes]. Given the many specialisation improvements and their potential for regression, we would very much appreciate testing and performance characterisation on downstream workloads. Note that while this release makes many improvements in the specialisation optimisation, polymorphic specialisation will remain disabled by default in the final release due to concern over regressions of the sort identified in [#26329]. Users needing more aggressive specialisation can explicitly enable this feature with the `-fpolymorphic-specialisation` flag. Depending upon our experience with 9.14.1, we may enable this feature by default in a later minor release. This is the third alpha release of 9.14.1. This comes later than expected in part due to work on a resolving a regression in the macOS 26 ([#26166]) which threatened the usability of the release. While a complete fix for this issue is not present in this alpha, we have done enough work to have confidence that it will be in finished for the release candidate which we expect should come the week of 27 October. We would like to thank the Zw3rk stake pool, Well-Typed, Mercury, Channable, Tweag I/O, Serokell, SimSpace, the Haskell Foundation, 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 have made the Haskell ecosystem what it is today. As always, do give this release a try and open a [ticket] if you see anything amiss. Cheers, - Ben [downloads.haskell.org] https://downloads.haskell.org/ghc/9.14.1-alpha3 [release notes]: https://downloads.haskell.org/ghc/9.14.1-alpha3/docs/users_guide/9.14.1-not… [ticket]: https://gitlab.haskell.org/ghc/homepage/-/issues/new [#26166]: https://gitlab.haskell.org/ghc/ghc/-/issues/26166 [#26329]: https://gitlab.haskell.org/ghc/ghc/-/issues/26329 [levels]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0682-e…

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