numpy on linux default to freethreaded Python in new environment

[hoxbro]

Solution to issue cannot be found in the documentation.

• I checked the documentation.

Issue

Not sure if this is the right place to report the problem, but when running the following conda create -n tmp numpy==2.4.2 it will pull in free-threaded Python version. Whereas 2.4.1 pulled in the non free threaded version.

❯ conda create -n tmp numpy==2.4.2
Retrieving notices: done
Channels:
 - conda-forge
Platform: linux-64
Collecting package metadata (repodata.json): done
Solving environment: done

## Package Plan ##

  environment location: /home/shh/.local/conda/envs/tmp

  added / updated specs:
    - numpy==2.4.2


The following packages will be downloaded:

    package                    |            build
    ---------------------------|-----------------
    numpy-2.4.2                |  py314hd4f4903_1         8.6 MB  conda-forge
    python-3.14.3              |he1279bd_1_cp314t        45.4 MB  conda-forge
    python_abi-3.14            |         8_cp314t           7 KB  conda-forge
    ------------------------------------------------------------
                                           Total:        53.9 MB

The following NEW packages will be INSTALLED:

  _openmp_mutex      conda-forge/linux-64::_openmp_mutex-4.5-20_gnu
  bzip2              conda-forge/linux-64::bzip2-1.0.8-hda65f42_9
  ca-certificates    conda-forge/noarch::ca-certificates-2026.2.25-hbd8a1cb_0
  icu                conda-forge/linux-64::icu-78.2-h33c6efd_0
  ld_impl_linux-64   conda-forge/linux-64::ld_impl_linux-64-2.45.1-default_hbd61a6d_101
  libblas            conda-forge/linux-64::libblas-3.11.0-5_h4a7cf45_openblas
  libcblas           conda-forge/linux-64::libcblas-3.11.0-5_h0358290_openblas
  libexpat           conda-forge/linux-64::libexpat-2.7.4-hecca717_0
  libffi             conda-forge/linux-64::libffi-3.5.2-h3435931_0
  libgcc             conda-forge/linux-64::libgcc-15.2.0-he0feb66_18
  libgfortran        conda-forge/linux-64::libgfortran-15.2.0-h69a702a_18
  libgfortran5       conda-forge/linux-64::libgfortran5-15.2.0-h68bc16d_18
  libgomp            conda-forge/linux-64::libgomp-15.2.0-he0feb66_18
  liblapack          conda-forge/linux-64::liblapack-3.11.0-5_h47877c9_openblas
  liblzma            conda-forge/linux-64::liblzma-5.8.2-hb03c661_0
  libmpdec           conda-forge/linux-64::libmpdec-4.0.0-hb03c661_1
  libopenblas        conda-forge/linux-64::libopenblas-0.3.30-pthreads_h94d23a6_4
  libsqlite          conda-forge/linux-64::libsqlite-3.51.2-hf4e2dac_0
  libstdcxx          conda-forge/linux-64::libstdcxx-15.2.0-h934c35e_18
  libuuid            conda-forge/linux-64::libuuid-2.41.3-h5347b49_0
  libzlib            conda-forge/linux-64::libzlib-1.3.1-hb9d3cd8_2
  ncurses            conda-forge/linux-64::ncurses-6.5-h2d0b736_3
  numpy              conda-forge/linux-64::numpy-2.4.2-py314hd4f4903_1
  openssl            conda-forge/linux-64::openssl-3.6.1-h35e630c_1
  python             conda-forge/linux-64::python-3.14.3-he1279bd_1_cp314t
  python_abi         conda-forge/noarch::python_abi-3.14-8_cp314t
  readline           conda-forge/linux-64::readline-8.3-h853b02a_0
  tk                 conda-forge/linux-64::tk-8.6.13-noxft_h366c992_103
  tzdata             conda-forge/noarch::tzdata-2025c-hc9c84f9_1
  zstd               conda-forge/linux-64::zstd-1.5.7-hb78ec9c_6

❯ conda create -n tmp numpy==2.4.1
Retrieving notices: done
Channels:
 - conda-forge
Platform: linux-64
Collecting package metadata (repodata.json): done
Solving environment: done

## Package Plan ##

  environment location: /home/shh/.local/conda/envs/tmp

  added / updated specs:
    - numpy==2.4.1


The following packages will be downloaded:

    package                    |            build
    ---------------------------|-----------------
    numpy-2.4.1                |  py314h2b28147_0         8.5 MB  conda-forge
    ------------------------------------------------------------
                                           Total:         8.5 MB

The following NEW packages will be INSTALLED:

  _openmp_mutex      conda-forge/linux-64::_openmp_mutex-4.5-20_gnu
  bzip2              conda-forge/linux-64::bzip2-1.0.8-hda65f42_9
  ca-certificates    conda-forge/noarch::ca-certificates-2026.2.25-hbd8a1cb_0
  icu                conda-forge/linux-64::icu-78.2-h33c6efd_0
  ld_impl_linux-64   conda-forge/linux-64::ld_impl_linux-64-2.45.1-default_hbd61a6d_101
  libblas            conda-forge/linux-64::libblas-3.11.0-5_h4a7cf45_openblas
  libcblas           conda-forge/linux-64::libcblas-3.11.0-5_h0358290_openblas
  libexpat           conda-forge/linux-64::libexpat-2.7.4-hecca717_0
  libffi             conda-forge/linux-64::libffi-3.5.2-h3435931_0
  libgcc             conda-forge/linux-64::libgcc-15.2.0-he0feb66_18
  libgfortran        conda-forge/linux-64::libgfortran-15.2.0-h69a702a_18
  libgfortran5       conda-forge/linux-64::libgfortran5-15.2.0-h68bc16d_18
  libgomp            conda-forge/linux-64::libgomp-15.2.0-he0feb66_18
  liblapack          conda-forge/linux-64::liblapack-3.11.0-5_h47877c9_openblas
  liblzma            conda-forge/linux-64::liblzma-5.8.2-hb03c661_0
  libmpdec           conda-forge/linux-64::libmpdec-4.0.0-hb03c661_1
  libopenblas        conda-forge/linux-64::libopenblas-0.3.30-pthreads_h94d23a6_4
  libsqlite          conda-forge/linux-64::libsqlite-3.51.2-hf4e2dac_0
  libstdcxx          conda-forge/linux-64::libstdcxx-15.2.0-h934c35e_18
  libuuid            conda-forge/linux-64::libuuid-2.41.3-h5347b49_0
  libzlib            conda-forge/linux-64::libzlib-1.3.1-hb9d3cd8_2
  ncurses            conda-forge/linux-64::ncurses-6.5-h2d0b736_3
  numpy              conda-forge/linux-64::numpy-2.4.1-py314h2b28147_0
  openssl            conda-forge/linux-64::openssl-3.6.1-h35e630c_1
  python             conda-forge/linux-64::python-3.14.3-h32b2ec7_101_cp314
  python_abi         conda-forge/noarch::python_abi-3.14-8_cp314
  readline           conda-forge/linux-64::readline-8.3-h853b02a_0
  tk                 conda-forge/linux-64::tk-8.6.13-noxft_h366c992_103
  tzdata             conda-forge/noarch::tzdata-2025c-hc9c84f9_1
  zstd               conda-forge/linux-64::zstd-1.5.7-hb78ec9c_6

Installed packages

# packages in environment at /home/shh/.local/conda:
#
# Name                           Version          Build                 Channel
_openmp_mutex                    4.5              20_gnu                conda-forge
_python_abi3_support             1.0              hd8ed1ab_2            conda-forge
anyio                            4.12.1           pyhcf101f3_0          conda-forge
archspec                         0.2.5            pyhd8ed1ab_0          conda-forge
argon2-cffi                      25.1.0           pyhd8ed1ab_0          conda-forge
argon2-cffi-bindings             25.1.0           py314h5bd0f2a_2       conda-forge
arrow                            1.4.0            pyhcf101f3_0          conda-forge
asttokens                        3.0.1            pyhd8ed1ab_0          conda-forge
async-lru                        2.2.0            pyhcf101f3_0          conda-forge
attrs                            25.4.0           pyhcf101f3_1          conda-forge
babel                            2.18.0           pyhcf101f3_0          conda-forge
backports.zstd                   1.3.0            py314h680f03e_0       conda-forge
beautifulsoup4                   4.14.3           pyha770c72_0          conda-forge
bleach                           6.3.0            pyhcf101f3_1          conda-forge
bleach-with-css                  6.3.0            hbca2aae_1            conda-forge
boltons                          25.0.0           pyhd8ed1ab_0          conda-forge
brotli-python                    1.2.0            py314h3de4e8d_1       conda-forge
bs4                              4.14.3           hd8ed1ab_0            conda-forge
bzip2                            1.0.8            hda65f42_9            conda-forge
c-ares                           1.34.6           hb03c661_0            conda-forge
ca-certificates                  2026.2.25        hbd8a1cb_0            conda-forge
cached-property                  1.5.2            hd8ed1ab_1            conda-forge
cached_property                  1.5.2            pyha770c72_1          conda-forge
certifi                          2026.2.25        pyhd8ed1ab_0          conda-forge
cffi                             2.0.0            py314h4a8dc5f_1       conda-forge
chardet                          5.2.0            pyhd8ed1ab_3          conda-forge
charset-normalizer               3.4.4            pyhd8ed1ab_0          conda-forge
click                            8.3.1            pyh8f84b5b_1          conda-forge
comm                             0.2.3            pyhe01879c_0          conda-forge
conda                            26.1.0           py314hdafbbf9_0       conda-forge
conda-build                      26.1.0           pyh31ec981_2          conda-forge
conda-index                      0.7.0            pyhd8ed1ab_0          conda-forge
conda-libmamba-solver            25.11.0          pyhd8ed1ab_1          conda-forge
conda-package-handling           2.4.0            pyh7900ff3_2          conda-forge
conda-package-streaming          0.12.0           pyhd8ed1ab_0          conda-forge
cpp-expected                     1.3.1            h171cf75_0            conda-forge
cpython                          3.14.3           py314hd8ed1ab_101     conda-forge
debugpy                          1.8.20           py314h42812f9_0       conda-forge
decorator                        5.2.1            pyhd8ed1ab_0          conda-forge
defusedxml                       0.7.1            pyhd8ed1ab_0          conda-forge
distro                           1.9.0            pyhd8ed1ab_1          conda-forge
evalidate                        2.0.5            pyhe01879c_0          conda-forge
exceptiongroup                   1.3.1            pyhd8ed1ab_0          conda-forge
executing                        2.2.1            pyhd8ed1ab_0          conda-forge
filelock                         3.24.3           pyhd8ed1ab_0          conda-forge
fmt                              12.1.0           hff5e90c_0            conda-forge
fqdn                             1.5.1            pyhd8ed1ab_1          conda-forge
frozendict                       2.4.7            py314h5bd0f2a_0       conda-forge
h11                              0.16.0           pyhcf101f3_1          conda-forge
h2                               4.3.0            pyhcf101f3_0          conda-forge
hpack                            4.1.0            pyhd8ed1ab_0          conda-forge
httpcore                         1.0.9            pyh29332c3_0          conda-forge
httpx                            0.28.1           pyhd8ed1ab_0          conda-forge
hyperframe                       6.1.0            pyhd8ed1ab_0          conda-forge
icu                              78.2             h33c6efd_0            conda-forge
idna                             3.11             pyhd8ed1ab_0          conda-forge
importlib-metadata               8.7.0            pyhe01879c_1          conda-forge
ipykernel                        7.2.0            pyha191276_1          conda-forge
ipython                          9.10.0           pyh53cf698_0          conda-forge
ipython_pygments_lexers          1.1.1            pyhd8ed1ab_0          conda-forge
isoduration                      20.11.0          pyhd8ed1ab_1          conda-forge
jedi                             0.19.2           pyhd8ed1ab_1          conda-forge
jinja2                           3.1.6            pyhcf101f3_1          conda-forge
json5                            0.13.0           pyhd8ed1ab_0          conda-forge
jsonpatch                        1.33             pyhd8ed1ab_1          conda-forge
jsonpointer                      3.0.0            pyhcf101f3_3          conda-forge
jsonschema                       4.26.0           pyhcf101f3_0          conda-forge
jsonschema-specifications        2025.9.1         pyhcf101f3_0          conda-forge
jsonschema-with-format-nongpl    4.26.0           hcf101f3_0            conda-forge
jupyter-lsp                      2.3.0            pyhcf101f3_0          conda-forge
jupyter_client                   8.8.0            pyhcf101f3_0          conda-forge
jupyter_core                     5.9.1            pyhc90fa1f_0          conda-forge
jupyter_events                   0.12.0           pyh29332c3_0          conda-forge
jupyter_server                   2.17.0           pyhcf101f3_0          conda-forge
jupyter_server_terminals         0.5.4            pyhcf101f3_0          conda-forge
jupyterlab                       4.5.5            pyhd8ed1ab_0          conda-forge
jupyterlab_code_formatter        3.0.3            pyhd8ed1ab_0          conda-forge
jupyterlab_pygments              0.3.0            pyhd8ed1ab_2          conda-forge
jupyterlab_server                2.28.0           pyhcf101f3_0          conda-forge
keyutils                         1.6.3            hb9d3cd8_0            conda-forge
krb5                             1.22.2           ha1258a1_0            conda-forge
lark                             1.3.1            pyhd8ed1ab_0          conda-forge
ld_impl_linux-64                 2.45.1           default_hbd61a6d_101  conda-forge
libarchive                       3.8.5            gpl_hc2c16d8_100      conda-forge
libblas                          3.11.0           5_h4a7cf45_openblas   conda-forge
libcblas                         3.11.0           5_h0358290_openblas   conda-forge
libcurl                          8.18.0           hcf29cc6_1            conda-forge
libedit                          3.1.20250104     pl5321h7949ede_0      conda-forge
libev                            4.33             hd590300_2            conda-forge
libexpat                         2.7.4            hecca717_0            conda-forge
libffi                           3.5.2            h9ec8514_0            conda-forge
libgcc                           15.2.0           he0feb66_18           conda-forge
libgcc-ng                        15.2.0           h69a702a_18           conda-forge
libgfortran                      15.2.0           h69a702a_18           conda-forge
libgfortran5                     15.2.0           h68bc16d_18           conda-forge
libgomp                          15.2.0           he0feb66_18           conda-forge
libiconv                         1.18             h3b78370_2            conda-forge
liblapack                        3.11.0           5_h47877c9_openblas   conda-forge
liblief                          0.17.1           hecca717_0            conda-forge
liblzma                          5.8.2            hb03c661_0            conda-forge
libmamba                         2.5.0            hd28c85e_0            conda-forge
libmamba-spdlog                  2.5.0            h12fcf84_0            conda-forge
libmambapy                       2.5.0            py314hcbd71af_0       conda-forge
libmpdec                         4.0.0            hb03c661_1            conda-forge
libnghttp2                       1.67.0           had1ee68_0            conda-forge
libnsl                           2.0.1            hb9d3cd8_1            conda-forge
libopenblas                      0.3.30           pthreads_h94d23a6_4   conda-forge
libsodium                        1.0.18           h36c2ea0_1            conda-forge
libsolv                          0.7.35           h9463b59_0            conda-forge
libsqlite                        3.51.2           h0c1763c_0            conda-forge
libssh2                          1.11.1           hcf80075_0            conda-forge
libstdcxx                        15.2.0           h934c35e_18           conda-forge
libstdcxx-ng                     15.2.0           hdf11a46_18           conda-forge
libuuid                          2.41.3           h5347b49_0            conda-forge
libxcrypt                        4.4.36           hd590300_1            conda-forge
libxml2                          2.15.1           he237659_1            conda-forge
libxml2-16                       2.15.1           hca6bf5a_1            conda-forge
libxslt                          1.1.43           h711ed8c_1            conda-forge
libzlib                          1.3.1            hb9d3cd8_2            conda-forge
lxml                             6.0.2            py314hae3bed6_2       conda-forge
lz4-c                            1.10.0           h5888daf_1            conda-forge
lzo                              2.10             h280c20c_1002         conda-forge
mamba                            2.5.0            h9835478_0            conda-forge
markdown-it-py                   4.0.0            pyhd8ed1ab_0          conda-forge
markupsafe                       3.0.3            pyh7db6752_0          conda-forge
matplotlib-inline                0.2.1            pyhd8ed1ab_0          conda-forge
mbedtls                          3.6.3.1          h5888daf_0            conda-forge
mdurl                            0.1.2            pyhd8ed1ab_1          conda-forge
menuinst                         2.4.2            py314hdafbbf9_0       conda-forge
mistune                          3.2.0            pyhcf101f3_0          conda-forge
msgpack-python                   1.1.2            py314h9891dd4_1       conda-forge
nbclient                         0.10.4           pyhd8ed1ab_0          conda-forge
nbconvert-core                   7.17.0           pyhcf101f3_0          conda-forge
nbformat                         5.10.4           pyhd8ed1ab_1          conda-forge
ncurses                          6.5              h2d0b736_3            conda-forge
nest-asyncio                     1.6.0            pyhd8ed1ab_1          conda-forge
nlohmann_json-abi                3.12.0           h0f90c79_1            conda-forge
nomkl                            1.0              h5ca1d4c_0            conda-forge
notebook-shim                    0.2.4            pyhd8ed1ab_1          conda-forge
numpy                            2.4.2            py314h2b28147_1       conda-forge
openssl                          3.6.1            h35e630c_1            conda-forge
overrides                        7.7.0            pyhd8ed1ab_1          conda-forge
packaging                        26.0             pyhcf101f3_0          conda-forge
pandas                           3.0.1            py314hb4ffadd_0       conda-forge
pandocfilters                    1.5.0            pyhd8ed1ab_0          conda-forge
parso                            0.8.6            pyhcf101f3_0          conda-forge
patch                            2.8              hb03c661_1002         conda-forge
patchelf                         0.17.2           h58526e2_0            conda-forge
pexpect                          4.9.0            pyhd8ed1ab_1          conda-forge
pip                              26.0.1           pyh145f28c_0          conda-forge
pkginfo                          1.12.1.2         pyhd8ed1ab_0          conda-forge
platformdirs                     4.9.2            pyhcf101f3_0          conda-forge
pluggy                           1.6.0            pyhf9edf01_1          conda-forge
prometheus_client                0.24.1           pyhd8ed1ab_0          conda-forge
prompt-toolkit                   3.0.52           pyha770c72_0          conda-forge
psutil                           7.2.2            py314h0f05182_0       conda-forge
ptyprocess                       0.7.0            pyhd8ed1ab_1          conda-forge
pure_eval                        0.2.3            pyhd8ed1ab_1          conda-forge
py-lief                          0.17.1           py314ha160325_0       conda-forge
pybind11-abi                     11               hc364b38_1            conda-forge
pycosat                          0.6.6            py314h5bd0f2a_3       conda-forge
pycparser                        2.22             pyh29332c3_1          conda-forge
pygments                         2.19.2           pyhd8ed1ab_0          conda-forge
pysocks                          1.7.1            pyha55dd90_7          conda-forge
python                           3.14.3           h32b2ec7_101_cp314    conda-forge
python-dateutil                  2.9.0.post0      pyhe01879c_2          conda-forge
python-fastjsonschema            2.21.2           pyhe01879c_0          conda-forge
python-gil                       3.14.3           h4df99d1_101          conda-forge
python-json-logger               2.0.7            pyhd8ed1ab_0          conda-forge
python-libarchive-c              5.3              pyhe01879c_1          conda-forge
python-tzdata                    2025.3           pyhd8ed1ab_0          conda-forge
python_abi                       3.14             8_cp314               conda-forge
pytz                             2025.2           pyhd8ed1ab_0          conda-forge
pyyaml                           6.0.3            py314h67df5f8_1       conda-forge
pyzmq                            27.1.0           py312hda471dd_2       conda-forge
readline                         8.3              h853b02a_0            conda-forge
referencing                      0.37.0           pyhcf101f3_0          conda-forge
reproc                           14.2.5.post0     hb9d3cd8_0            conda-forge
reproc-cpp                       14.2.5.post0     h5888daf_0            conda-forge
requests                         2.32.5           pyhcf101f3_1          conda-forge
rfc3339-validator                0.1.4            pyhd8ed1ab_1          conda-forge
rfc3986-validator                0.1.1            pyh9f0ad1d_0          conda-forge
rfc3987-syntax                   1.1.0            pyhe01879c_1          conda-forge
rich                             14.3.3           pyhcf101f3_0          conda-forge
rich-click                       1.9.7            pyh8f84b5b_0          conda-forge
ripgrep                          15.1.0           hdab8a38_0            conda-forge
rpds-py                          0.30.0           py314h2e6c369_0       conda-forge
ruamel.yaml                      0.18.17          py314h0f05182_2       conda-forge
ruamel.yaml.clib                 0.2.15           py314h0f05182_1       conda-forge
send2trash                       2.1.0            pyha191276_1          conda-forge
setuptools                       82.0.0           pyh332efcf_0          conda-forge
simdjson                         4.2.4            hb700be7_0            conda-forge
six                              1.17.0           pyhe01879c_1          conda-forge
sniffio                          1.3.1            pyhd8ed1ab_2          conda-forge
soupsieve                        2.8.3            pyhd8ed1ab_0          conda-forge
spdlog                           1.17.0           hab81395_1            conda-forge
stack_data                       0.6.3            pyhd8ed1ab_1          conda-forge
terminado                        0.18.1           pyhc90fa1f_1          conda-forge
tinycss2                         1.4.0            pyhd8ed1ab_0          conda-forge
tk                               8.6.13           noxft_ha0e22de_103    conda-forge
tomli                            2.4.0            pyhcf101f3_0          conda-forge
tornado                          6.5.4            py314h7b0bd38_0       conda-forge
tqdm                             4.67.3           pyh8f84b5b_0          conda-forge
traitlets                        5.14.3           pyhd8ed1ab_1          conda-forge
truststore                       0.10.4           pyhcf101f3_0          conda-forge
typing-extensions                4.15.0           h396c80c_0            conda-forge
typing_extensions                4.15.0           pyhcf101f3_0          conda-forge
typing_utils                     0.1.0            pyhd8ed1ab_1          conda-forge
tzdata                           2025c            hc9c84f9_1            conda-forge
uri-template                     1.3.0            pyhd8ed1ab_1          conda-forge
urllib3                          2.6.3            pyhd8ed1ab_0          conda-forge
wcwidth                          0.6.0            pyhd8ed1ab_0          conda-forge
webcolors                        25.10.0          pyhd8ed1ab_0          conda-forge
webencodings                     0.5.1            pyhd8ed1ab_3          conda-forge
websocket-client                 1.9.0            pyhd8ed1ab_0          conda-forge
wheel                            0.46.3           pyhd8ed1ab_0          conda-forge
yaml                             0.2.5            h280c20c_3            conda-forge
yaml-cpp                         0.8.0            h3f2d84a_0            conda-forge
zeromq                           4.3.5            h59595ed_1            conda-forge
zipp                             3.23.0           pyhcf101f3_1          conda-forge
zstandard                        0.25.0           py314h0f05182_1       conda-forge
zstd                             1.5.7            hb78ec9c_6            conda-forge

Environment info

active environment : base
    active env location : /home/shh/.local/conda
            shell level : 0
       user config file : /home/shh/.condarc
 populated config files : /home/shh/.local/conda/.condarc
                          /home/shh/.config/conda/.condarc
          conda version : 26.1.0
    conda-build version : 26.1.0
         python version : 3.14.3.final.0
                 solver : libmamba (default)
       virtual packages : __archspec=1=zen3
                          __conda=26.1.0=0
                          __cuda=13.1=0
                          __glibc=2.43=0
                          __linux=6.18.9=0
                          __unix=0=0
       base environment : /home/shh/.local/conda  (writable)
      conda av data dir : /home/shh/.local/conda/etc/conda
  conda av metadata url : None
           channel URLs : https://conda.anaconda.org/conda-forge/linux-64
                          https://conda.anaconda.org/conda-forge/noarch
          package cache : /home/shh/.local/conda/pkgs
                          /home/shh/.conda/pkgs
       envs directories : /home/shh/.local/conda/envs
                          /home/shh/.conda/envs
    temporary directory : /tmp
               platform : linux-64
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                UID:GID : 1000:1000
             netrc file : None
           offline mode : False

[h-vetinari]

Generally, I think you should specify a python version yourself. Just relying that conda create -n tmp numpy brings in a specific python version is not a reasonable expectation IMO.

That said,

python-feedstock/recipe/meta.yaml

Lines 135 to 138 in 02184ce

	track_features:
	{% if freethreading == "yes" %}
	- py_freethreading
	{% endif %}

should ensure that the non-freethreading version gets priority.

[hoxbro]

I just reduced the problem down, this also conda create -n tmp numpy==2.4.2 python=3.14 pulls in free-threaded python, whereas this does not conda create -n tmp numpy==2.4.1 python=3.14

We noticed the problem in our CI https://github.com/holoviz/panel/actions/runs/22447620548/job/65006543402#step:3:520

[isuruf]

@hoxbro, this seems like a solver issue since it's not reproducible with classic conda solver. For libmamba: https://github.com/mamba-org/mamba and for rattler https://github.com/conda/rattler. I could reproduce with both these solvers.

[LourensVeen]

I'm running into this with netcdf4. It seems that these packages have multiple builds, some with python_abi 3.14.* *_cp314t (the free threading Python) and some with python_abi 3.14.* *_cp314 (the GIL one). The versions and build numbers are the same, and conda/conda#5770 suggests that conda will then sort by timestamp.

For numpy 2.4.1, the build numbers are all 0, and the most recent timestamp is that of py314hda7dee8_0, which is a non-free threading one. For numpy 2.4.2, the highest build number is 1, and the most recent build is py314hd4f4903_1, which is a free-threading one.

So if you install python numpy==2.4.1, then you get a GIL Python, and if you install python numpy==2.4.2 then you get a free threading Python. NetCDF4 1.7.4 has a similar issue, with the free threading build being slightly newer than than the GIL one.

Considering that there are likely Python packages that don't work with a free threading implementation, shouldn't the default be to install the GIL version, with conda installing a free threading version only if requested explicitly via conda install python-freethreading? That's what I would expect to happen at least.

[isuruf]

As I said in my comment above, please open an issue in https://github.com/mamba-org/mamba and https://github.com/conda/rattler

[LourensVeen]

I read that, but I don't see how it would help.

Conda currently sorts packages either by build string or first by timestamp and then by build string, and perhaps mamba and rattler do it differently (and if so then I guess that's a bug that I can report), but since the timestamp and build id are essentially random, the results will seem random from the user perspective regardless.

If the solution is for everyone to stop doing conda install python and instead always do either conda install python-gil or conda install python-freethreading then I'll start teaching my users to do that.

But given that there's probably a lot of Python software out there that doesn't work correctly on a free threading Python, having the GIL version be the default (i.e. build number 100+n) may be a good idea?

Apologies, I see now that we actually have this. I'll make a mamba issue.