GHC 10.0.1-alpha1 is now available

wz1000 - 2026-09-18

The GHC developers are very pleased to announce the availability of the first alpha prerelease of GHC 10.0.1. Binary distributions, source distributions, and documentation are available at downloads.haskell.org and via GHCup.

GHC 10.0 will bring a number of new features and improvements, including:

  • The default language edition is now GHC2024 (GHC Proposal #632, #26039).

  • Type and Constraint are now completely distinct types, just as much as Int and Bool (#24279).

  • The new QualifiedStrings language extension (GHC Proposal #723) allows string literals to be qualified using module qualification syntax, so that M."my string" desugars toM.fromString "my string".

  • The treatment of static forms has been simplified, implementing GHC Proposal #732 (#26556). The free term variables of (static e) must now be bound at top level.

  • -fpolymorphic-specialisation is now (re)enabled by default (#23559),

  • Bytecode can now be written to disk with -fwrite-byte-code and packaged into bytecode libraries with -bytecodelib, which the interpreter can use to satisfy package dependencies (#26298).

  • Executables can now be properly statically linked with the new -fully-static and -static-external flags (#26434).

  • SIMD support in the AArch64 native code generator (#26536).

  • A new poll I/O manager, which is now the default in the single-threaded RTS on all POSIX platforms except macOS (!9677).

  • Version 2 of the GHC Jobserver Protocol for GHC’s -jsem jobserver on Linux and other POSIX platforms (#25087, #27253). This is sadly a necessary breaking change. -jsem requires cabal-install 3.18 or later, and is otherwise ignored with a warning, falling back to sequential compilation.

  • Changes to base:

    • GHC.Num.{BigNat,Integer,Natural} are no longer exposed (CLC #359) and GHC internals in GHC.Num are deprecated (CLC #360).

    • Data.List.init and Data.List.last now carry an x-partial warning (CLC #292).

  • The minimum bootstrap compiler is now GHC 9.10, LLVM versions up to 23 are supported (#26813, #27764), and the Debian 9, Debian 10, Ubuntu 18.04 and Ubuntu 20.04 bindists have been dropped in favour of a new Debian 13 bindist (#25876).

  • … and many more

A full accounting of changes can be found in the release notes. See the migration guide for guidance on migrating programs to this release. As always, GHC’s release status, including planned future releases, can be found on the GHC Wiki status.

Given the many changes in this major release, we would very much appreciate testing on downstream workloads.

GHC development is sponsored by:

We would like to thank 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.