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ROOT

ANALYTICS
Velocity6.3

Data analysis framework for large scale scientific data processing

root.cern ↗

ROOT 6.42 rebuilds its Python interface on cppjit and moves Cling to LLVM 22.

hepscientific-computingpython-bindingsllvmcerncpp
◆Current state
CERN's ROOT has published the first release candidate of 6.42.00, with the final scheduled for the end of November 2026. The release notes name two large changes: Cling, ROOT's C++ interpreter, moves to LLVM 22, and the Python interface is completely overhauled to rely on cppjit, which the team says brings more functionality, better runtime performance and simpler code. More than 180 tracker items were addressed. Until now the feed had been 6.40 LTS patches and backports to older series.
◆Where it's heading
After a stretch of LTS maintenance, 6.42 is a foundational release: the interpreter and the Python bindings are the two layers most analysis code runs through. Replacing the PyROOT machinery is the change most users will notice, since much HEP analysis is now written in Python. The older series keep receiving patches, so 6.40 LTS users won't be forced to move.
◆Prediction
The release candidate exists to test these changes, so expect further rc builds or a 6.42.00 final around the end of November, with Python-interface fixes the most likely content of the first 6.42 patches.

◆Recent moves

  1. 11d ago

    6.42 rc1: Python interface rebuilt on cppjit, Cling on LLVM 22

    ⚡ SPARK

    The first 6.42 release candidate ends the LTS-patch stretch with a foundational change: Cling on LLVM 22 and a rebuilt Python interface on cppjit, with more than 180 tracker items addressed. Final release is scheduled for the end of November.

    View source ↗
  2. 11d ago

    Version bump to 6.41.99 ahead of the 6.42 RC

    Version files bumped to 6.41.99, the placeholder tag before the 6.42 release candidate. No user-facing change.

    View source ↗
  3. 2mo ago

    ROOT 6.36.14: minor patch for STS series

    A minor patch for the 6.36 series with details linked externally. The 6.36 line is a short-term support series now superseded by 6.40 LTS; continued patches here serve users who haven't migrated yet.

    View source ↗
  4. 2mo ago

    v6-40-04

    The 6.40.04 patch addresses 25+ tracked issues across the LTS series, most notably a CMake 4.4 configuration failure that was blocking builds on newer toolchains. Substantive correctness fixes land in RooFit (RooBinIntegrator, ExtendPdf range fits), NTuple (double-free on RVec resize, wrong type name in streamer fields), and Minuit2 (Hessian robustness). This is a meaningful patch with real impact on analysis correctness, not just infrastructure tidying.

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  5. 4mo ago

    ROOT 6.32.24: minor patch for STS series

    Minor fixes for the 6.32 STS series, details at the release notes link. A legacy maintenance drop for users on an older supported branch.

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  6. 4mo ago

    ROOT 6.30.12: minor patch for STS series

    Minor fixes for the 6.30 STS series. A legacy maintenance drop for users on an older supported branch.

    View source ↗