⚠️ CI failed on Linux_free_threaded.pylatest_free_threaded (last failure: Jan 03, 2026) ⚠️

**CI is still failing on [Linux_free_threaded.pylatest_free_threaded](https://dev.azure.com/scikit-learn/scikit-learn/_build/results?buildId=83868&view=logs&j=c10228e9-6cf7-5c29-593f-d74f893ca1bd)** (Jan 03, 2026)
- test_response_values_output_shape_[estimator10-predict-multiclass-expected_shape10]

COMMENT:
December 23, Segmentation fault [build log](https://dev.azure.com/scikit-learn/scikit-learn/_build/results?buildId=83623&view=logs&jobId=c10228e9-6cf7-5c29-593f-d74f893ca1bd&j=c10228e9-6cf7-5c29-593f-d74f893ca1bd&t=c073cbc0-0094-54ff-6a32-c70e36da1f8e)

```
utils/tests/test_random.py ·····                                         [ 97%]
utils/tests/test_response.py ··········································· [ 97%]
······Fatal Python error: Segmentation fault

<Cannot show all threads while the GIL is disabled>
Stack (most recent call first):
  File "/home/vsts/work/1/s/sklearn/tree/_classes.py", line 534 in predict
  File "/home/vsts/work/1/s/sklearn/utils/_response.py", line 244 in _get_response_values
  File "/home/vsts/work/1/s/sklearn/utils/tests/test_response.py", line 446 in test_response_values_output_shape_
  File "/home/vsts/miniforge3/envs/testvenv/lib/python3.14t/site-packages/pytest_run_parallel/plugin.py", line 80 in closure
  File "/home/vsts/miniforge3/envs/testvenv/lib/python3.14t/threading.py", line 1024 in run
  File "/home/vsts/miniforge3/envs/testvenv/lib/python3.14t/threading.py", line 1082 in _bootstrap_inner
  File "/home/vsts/miniforge3/envs/testvenv/lib/python3.14t/threading.py", line 1044 in _bootstrap

Current thread's C stack trace (most recent call first):
  Binary file "python", at _Py_DumpStack+0x4a [0x556c74277c7f]
  Binary file "python", at +0x16a4a5 [0x556c742824a5]
  Binary file "/lib/x86_64-linux-gnu/libc.so.6", at +0x42520 [0x7f0097442520]
  Binary file "/home/vsts/work/1/s/build/cp314t/sklearn/tree/_tree.cpython-314t-x86_64-linux-gnu.so", at +0x2821b [0x7f007f2d721b]
  Binary file "/home/vsts/work/1/s/build/cp314t/sklearn/tree/_tree.cpython-314t-x86_64-linux-gnu.so", at +0x28e45 [0x7f007f2d7e45]
  Binary file "/home/vsts/work/1/s/build/cp314t/sklearn/tree/_tree.cpython-314t-x86_64-linux-gnu.so", at +0x2c2e5 [0x7f007f2db2e5]
  Binary file "/home/vsts/work/1/s/build/cp314t/sklearn/tree/_tree.cpython-314t-x86_64-linux-gnu.so", at +0x2cb55 [0x7f007f2dbb55]
  Binary file "python", at PyObject_Vectorcall+0x37 [0x556c742bc317]
  Binary file "python", at _PyEval_EvalFrameDefault+0xd95 [0x556c742d1875]
  Binary file "python", at +0x1b5540 [0x556c742cd540]
  Binary file "python", at +0x223a9e [0x556c7433ba9e]
  Binary file "python", at +0x2b2ae8 [0x556c743caae8]
  Binary file "python", at +0x2fca01 [0x556c74414a01]
  Binary file "python", at _PyEval_EvalFrameDefault+0x3a67 [0x556c742d4547]
  Binary file "python", at +0x1b5540 [0x556c742cd540]
  Binary file "python", at +0x223a9e [0x556c7433ba9e]
  Binary file "python", at +0x2fc209 [0x556c74414209]
  Binary file "python", at +0x2fc125 [0x556c74414125]
  Binary file "/lib/x86_64-linux-gnu/libc.so.6", at +0x94ac3 [0x7f0097494ac3]
  Binary file "/lib/x86_64-linux-gnu/libc.so.6", at +0x1268c0 [0x7f00975268c0]

Extension modules: numpy._core._multiarray_umath, numpy.linalg._umath_linalg, sklearn.__check_build._check_build, cython.cimports.libc.math, _cyutility, scipy._cyutility, scipy._lib._ccallback_c, numpy.random._common, numpy.random.bit_generator, numpy.random._bounded_integers, numpy.random._pcg64, numpy.random._mt19937, numpy.random._generator, numpy.random._philox, numpy.random._sfc64, numpy.random.mtrand, scipy.sparse._sparsetools, _csparsetools, scipy.sparse._csparsetools, scipy.special._ufuncs_cxx, scipy.special._ellip_harm_2, scipy.special._special_ufuncs, scipy.special._gufuncs, scipy.special._ufuncs, scipy.special._specfun, scipy.special._comb, scipy.linalg._fblas, scipy.linalg._flapack, scipy.linalg.cython_lapack, scipy.linalg._cythonized_array_utils, scipy.linalg._solve_toeplitz, scipy.linalg._decomp_lu_cython, scipy.linalg._matfuncs_schur_sqrtm, scipy.linalg._matfuncs_expm, scipy.linalg._linalg_pythran, scipy.linalg.cython_blas, scipy.linalg._decomp_update, scipy.sparse.linalg._dsolve._superlu, scipy.sparse.linalg._eigen.arpack._arpack, scipy.sparse.linalg._propack._spropack, scipy.sparse.linalg._propack._dpropack, scipy.sparse.linalg._propack._cpropack, scipy.sparse.linalg._propack._zpropack, scipy.spatial._ckdtree, scipy._lib.messagestream, scipy.spatial._qhull, scipy.spatial._voronoi, scipy.spatial._hausdorff, scipy.spatial._distance_wrap, scipy.spatial.transform._rotation, scipy.spatial.transform._rigid_transform, scipy.optimize._group_columns, scipy.optimize._trlib._trlib, scipy.optimize._lbfgsb, _moduleTNC, scipy.optimize._moduleTNC, scipy.optimize._slsqplib, scipy.optimize._minpack, scipy.optimize._lsq.givens_elimination, scipy.optimize._zeros, scipy._lib._uarray._uarray, scipy.linalg._decomp_interpolative, scipy.optimize._bglu_dense, scipy.optimize._lsap, scipy.optimize._direct, scipy.integrate._odepack, scipy.integrate._quadpack, scipy.integrate._vode, scipy.integrate._dop, scipy.integrate._lsoda, scipy.interpolate._fitpack, scipy.interpolate._dfitpack, scipy.interpolate._dierckx, scipy.interpolate._ppoly, scipy.interpolate._interpnd, scipy.interpolate._rbfinterp_pythran, scipy.interpolate._rgi_cython, scipy.special.cython_special, scipy.stats._stats, scipy.stats._biasedurn, scipy.stats._stats_pythran, scipy.stats._levy_stable.levyst, scipy.stats._ansari_swilk_statistics, scipy.sparse.csgraph._tools, scipy.sparse.csgraph._shortest_path, scipy.sparse.csgraph._traversal, scipy.sparse.csgraph._min_spanning_tree, scipy.sparse.csgraph._flow, scipy.sparse.csgraph._matching, scipy.sparse.csgraph._reordering, scipy.stats._sobol, scipy.stats._qmc_cy, scipy.stats._rcont.rcont, scipy.stats._qmvnt_cy, scipy.ndimage._nd_image, scipy.ndimage._rank_filter_1d, _ni_label, scipy.ndimage._ni_label, sklearn._cyutility, sklearn.utils._isfinite, sklearn.utils.sparsefuncs_fast, sklearn.utils.murmurhash, sklearn.utils._openmp_helpers, sklearn.preprocessing._csr_polynomial_expansion, sklearn.preprocessing._target_encoder_fast, scipy.io.matlab._mio_utils, scipy.io.matlab._streams, scipy.io.matlab._mio5_utils, sklearn.datasets._svmlight_format_fast, sklearn.utils._random, sklearn.utils._vector_sentinel, sklearn.feature_extraction._hashing_fast, _loss, sklearn._loss._loss, sklearn.metrics.cluster._expected_mutual_info_fast, sklearn.metrics._dist_metrics, sklearn.metrics._pairwise_distances_reduction._datasets_pair, sklearn.utils._cython_blas, sklearn.metrics._pairwise_distances_reduction._base, sklearn.metrics._pairwise_distances_reduction._middle_term_computer, sklearn.utils._heap, sklearn.utils._sorting, sklearn.metrics._pairwise_distances_reduction._argkmin, sklearn.metrics._pairwise_distances_reduction._argkmin_classmode, sklearn.metrics._pairwise_distances_reduction._radius_neighbors, sklearn.metrics._pairwise_distances_reduction._radius_neighbors_classmode, sklearn.metrics._pairwise_fast, sklearn.utils._fast_dict, sklearn.cluster._hierarchical_fast, sklearn.cluster._k_means_common, sklearn.cluster._k_means_elkan, sklearn.cluster._k_means_lloyd, sklearn.cluster._k_means_minibatch, sklearn.cluster._dbscan_inner, sklearn.neighbors._partition_nodes, sklearn.neighbors._ball_tree, sklearn.neighbors._kd_tree, sklearn.utils.arrayfuncs, sklearn.utils._seq_dataset, sklearn.linear_model._cd_fast, sklearn.linear_model._sag_fast, sklearn.svm._liblinear, sklearn.svm._libsvm, sklearn.svm._libsvm_sparse, sklearn.utils._weight_vector, sklearn.linear_model._sgd_fast, sklearn.decomposition._online_lda_fast, sklearn.decomposition._cdnmf_fast, sklearn.cluster._hdbscan._tree, sklearn.cluster._hdbscan._linkage, sklearn.cluster._hdbscan._reachability, sklearn._isotonic, sklearn.tree._utils, sklearn.tree._tree, sklearn.tree._partitioner, sklearn.tree._splitter, sklearn.tree._criterion, sklearn.neighbors._quad_tree, sklearn.manifold._barnes_hut_tsne, sklearn.manifold._utils, scipy.cluster._vq, scipy.cluster._hierarchy, scipy.cluster._optimal_leaf_ordering, sklearn.ensemble._gradient_boosting, sklearn.ensemble._hist_gradient_boosting.common, sklearn.ensemble._hist_gradient_boosting._gradient_boosting, sklearn.ensemble._hist_gradient_boosting._binning, sklearn.ensemble._hist_gradient_boosting._bitset, sklearn.ensemble._hist_gradient_boosting.histogram, sklearn.ensemble._hist_gradient_boosting._predictor, sklearn.ensemble._hist_gradient_boosting.splitting, sklearn.svm._newrand, sklearn.utils._typedefs (total: 173)
/home/vsts/work/1/s/build_tools/azure/test_script.sh: line 92:  3262 Segmentation fault      (core dumped) python -m pytest --showlocals --durations=20 --junitxml=test-data.xml -o junit_family=legacy --parallel-threads 2 --iterations 1 --pyargs sklearn

```

Labels: Bug