What's Changed

Platforms

• Add Python 3.14 support.

Dependencies

C++

• abseil-cpp=20250814.1
• Protobuf=v33.1
• HiGHS=v1.12.0
• SCIP=v10.0.0

Routing

• Improved routing performance and search event support (at optimal).
• Improved Doxygen documentation.
• Reworked routing samples (#4590).
• Exported filters update and other improvements from main.

CP-SAT

• Improvements to the no_overlap_2d constraint (presolve, propagation, and cuts).
• Detect, store and use precedences in presolve, propagation, and cuts.
• Extensive work on LRAT proof production and checking.
• Improve linear1 and linear2 encodings and processing.
• Support for set variables and constraints (experimental).
• Extend support for enforcement literals to more constraints.
• Optimize Python layer, speed up proto generation, and improve typing support (#4733).
• Improve support for gil-less Python 3.14.
• Add soft constraint examples.
• Improve shared tree workers and clause sharing.
• Print solution on SIGTERM.
• Fix various bugs and improve heuristics (#4907, #4746, #4839, #4929, #4743, #4693, #4666, #4654).
• Improved scheduling cuts and memory management.

MathOpt

• Pass solution hint to HiGHS from MathOpt (#4737).
• Propagate nullability and add nullability to SolveInterrupter (#4959, #4958).
• Rework GSCIP and solver integration; fix Windows build issues.
• Backport various improvements from main.

Linear Solver

• Refactor MPSolver interface registration to include runtime readiness checks (#4973).
• Add lazy constraints support in XPRESS interface.
• MPSolver-XPRESS: Remove superfluous calls to XPRSloadlp and XPRScreateprob (#4667).
• Support for constant terms in DoubleLinearExpr::AddExpression.
• Added support for Gurobi 12.0.2, 12.0.3, and 13.0.0.
• Fixed XPRESS compilation on Windows and updated Bazel build (#4945, #4956).
• Support SCIP 10.0.0.

Build & Dependencies

• Bumped dependencies: Abseil 20250512.0, Protobuf v31.1, gTest 1.17.0, Benchmark 1.9.2.
• Dropped support for Python 3.8; minimum version is now 3.9.
• Modernize Bazel build and improve Java, .NET, and Julia support (#4885, #4928, #4879).
• Added automated ccache support in CMake.
• Fix Python build with BUILD_TESTING=OFF.

Other

• Added space_saving_most_frequent utility.
• Column generation Bin Packing heuristic based on CFT (#4639).
• Reworked SortedDisjointIntervalList to support copy, deepcopy, and iterators in Python.
• Added ORToolsBinaries.jl for Julia.
• PDLP: Fix test when using pytest 8.4.0.
• Removed fuzztest support from OR-Tools (#4938).%

Changes (PR)

• MPSolver-XPRESS: Remove superfluous calls to XPRSloadlp and XPRScreateprob by @pet-mit in https://github.com/google/or-tools/pull/4667
• cmake: update HiGHS to 1.11 by @galabovaa in https://github.com/google/or-tools/pull/4670
• bazel: Bump HiGHS to 1.11 by @galabovaa in https://github.com/google/or-tools/pull/4671
• cmake: Add support for custom protoc executable via OR_TOOLS_PROTOC_EXECUTABLE by @clementperon in https://github.com/google/or-tools/pull/4679
• Fix compilation with iterator with C++ 17 by @clementperon in https://github.com/google/or-tools/pull/4696
• Fix compat with protobuf < 5.26 by @clementperon in https://github.com/google/or-tools/pull/4697
• Format py files by @gchatelet in https://github.com/google/or-tools/pull/4702
• Turn some .i files into .swig by @gchatelet in https://github.com/google/or-tools/pull/4712
• Column generation Bin Packing heuristic based on CFT by @c4v4 in https://github.com/google/or-tools/pull/4639
• Add MPConstraint::Clear() to C# wrapper by @rs-blade in https://github.com/google/or-tools/pull/4728
• Backport trivial changes by @gchatelet in https://github.com/google/or-tools/pull/4734
• Backport string_view_migration.h by @gchatelet in https://github.com/google/or-tools/pull/4735
• Fix bazel load rules by @gchatelet in https://github.com/google/or-tools/pull/4740
• Fix load statements by @gchatelet in https://github.com/google/or-tools/pull/4742
• Pass solution hint to HiGHS from mathopt by @pavlomuts in https://github.com/google/or-tools/pull/4737
• build(deps): bump urllib3 from 2.2.2 to 2.5.0 in /bazel in the pip group across 1 directory by @dependabot[bot] in https://github.com/google/or-tools/pull/4700
• math_opt: only run SCIP tests if enabled by @flokli in https://github.com/google/or-tools/pull/4745
• build(deps): bump actions/checkout from 4 to 5 in the github-actions group by @dependabot[bot] in https://github.com/google/or-tools/pull/4752
• Remove unnecessary exports_files by @gchatelet in https://github.com/google/or-tools/pull/4757
• build(deps): bump actions/setup-java from 4 to 5 in the github-actions group by @dependabot[bot] in https://github.com/google/or-tools/pull/4763
• build(deps): bump the github-actions group with 2 updates by @dependabot[bot] in https://github.com/google/or-tools/pull/4817
• build(deps): bump actions/checkout from 5 to 6 in the github-actions group by @dependabot[bot] in https://github.com/google/or-tools/pull/4925
• build(deps): bump jupyterlab from 4.4.3 to 4.4.8 in /bazel in the pip group across 1 directory by @dependabot[bot] in https://github.com/google/or-tools/pull/4927

New Contributors

• @clementperon made their first contribution in https://github.com/google/or-tools/pull/4679
• @rs-blade made their first contribution in https://github.com/google/or-tools/pull/4728
• @pavlomuts made their first contribution in https://github.com/google/or-tools/pull/4737
• @flokli made their first contribution in https://github.com/google/or-tools/pull/4745

Known issues

Wrappers (.Net, Java, Python)

• routing: SetAllowedVehiclesForIndex not working in wrappers (changed parameters) #4982

• sat: solver.status_name() raises TypeError: 'ortools.sat.python.cp_model_helper.CpSolverStatus' object is not callable #4985

• sat: CpSolver.Solve() callback breaking argument change #4988

MacOS

You must use swig <= 4.3.1 to avoid Director issue on python, unfortunately homebrew only provides the "broken" swig 4.4.1 to install swig manually: first download swig 4.3.1: https://sourceforge.net/projects/swig/files/swig/swig-4.3.1/

# Optional uninstall brew version if any
brew uninstall swig

# Build swig from source and install it
cd /tmp
tar xzvf ~/Downloads/swig-4.3.1.tar.gz
cd swig-4.3.1/
./configure --prefix=${HOME}/swig-4.3.1
make
make install
export PATH="${HOME}/swig-4.3.1/bin:$PATH"
# To check
command -v swig
swig --version

ref: https://github.com/swig/swig/issues/3279

Full Changelog: https://github.com/google/or-tools/compare/v9.14...v9.15