mamba sometimes solves differently (and incorrectly) WRT channel priority, compared to conda #4092
Description
Troubleshooting docs
- My problem is not solved in the Troubleshooting docs
Anaconda default channels
- I do NOT use the Anaconda default channels (pkgs/* etc.)
How did you install Mamba?
Mambaforge or latest Miniforge
Search tried in issue tracker
Yes
Latest version of Mamba
- My problem is not solved with the latest version
Tried in Conda?
I do not have this problem with Conda, just with Mamba
Describe your issue
In certain circumstances, the mamba tool doesn't respect channel priority, in cases where the conda tool does.
I am trying to use a scientific piece of software that layers flyem-forge on top of conda-forge, and some packages in conda-forge are missing dynamic libraries in their builds that the scientific software needs). The ideal is that if a package exists in flyem-forge, it's used, otherwise conda-forge is used.
Command:
CONDA_SUBDIR=osx-64 mamba create -y -n neutu --strict-channel-priority -c flyem-forge -c conda-forge neutu-develop --dry-run
VS
CONDA_SUBDIR=osx-64 conda create -y -n neutu --strict-channel-priority -c flyem-forge -c conda-forge neutu-develop --dry-run
The former (with mamba) has it prefer, for no good reason, the conda-forge version of draco, while the latter behaves as expected and has it use the flyem-forge version. Note that it is possible to force mamba to use the flyem-forge versions of packages using flyem-forge::draco and whatnot, but that's messy/noisy.
mamba info / micromamba info
libmamba version : 2.3.3
mamba version : 2.3.3
curl version : libcurl/8.16.0 OpenSSL/3.5.4 zlib/1.3.1 zstd/1.5.7 libssh2/1.11.1 nghttp2/1.67.0
libarchive version : libarchive 3.8.2 zlib/1.3.1 liblzma/5.8.1 bz2lib/1.0.8 liblz4/1.10.0 libzstd/1.5.7 liblzo2/2.10 CommonCrypto/system libb2/bundled
envs directories : /Users/pgunn/miniforge3/envs
package cache : /Users/pgunn/miniforge3/pkgs
/Users/pgunn/.mamba/pkgs
environment : base
env location : /Users/pgunn/miniforge3
user config files : /Users/pgunn/.mambarc
populated config files : /Users/pgunn/miniforge3/.condarc
virtual packages : __unix=0=0
__osx=15.2=0
__archspec=1=arm64
channels : https://conda.anaconda.org/conda-forge/noarch
https://conda.anaconda.org/conda-forge/osx-arm64
base environment : /Users/pgunn/miniforge3
platform : osx-arm64Logs
skuld:~ pgunn$ CONDA_SUBDIR=osx-64 mamba create -y -n managed_neutu -v --strict-channel-priority -c flyem-forge -c conda-forge neutu-develop --dry-run
info libmamba Searching index cache file for repo 'conda-forge/noarch'
info libmamba Valid cache found for 'conda-forge/noarch': 1
conda-forge/noarch Using cache
info libmamba Searching index cache file for repo 'conda-forge/osx-64'
info libmamba Valid cache found for 'conda-forge/osx-64': 1
conda-forge/osx-64 Using cache
info libmamba Searching index cache file for repo 'flyem-forge/noarch'
info libmamba Valid cache found for 'flyem-forge/noarch': 0
info libmamba Expired cache (or invalid mod/etag headers) found at '"/Users/pgunn/miniforge3/pkgs"'
info libmamba Searching index cache file for repo 'flyem-forge/osx-64'
info libmamba Valid cache found for 'flyem-forge/osx-64': 0
info libmamba Expired cache (or invalid mod/etag headers) found at '"/Users/pgunn/miniforge3/pkgs"'
info libmamba Checking for CA certificates at the root prefix: "/Users/pgunn/miniforge3/ssl/cacert.pem"
info libmamba Using CA certificates from `conda-forge::ca-certificates` installed in the root prefix (i.e "/Users/pgunn/miniforge3/ssl/cacert.pem")
[+] 0.1s
flyem-forge/noarch ━━━━━━━━━━━╸━━━━━━━━━━━━━━━╸━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 0.0 B / ??.?MB @ ??.?MB/s 0.0s
flyem-forge/osx-64 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╸━━━━━━━━━━━━━━━╸━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 0.0 B / ??.?MB @ ??.?MB/s 0.0sinfo libmamba Attempting to read libsolv solv file "/Users/pgunn/miniforge3/pkgs/cache/eb045dd1.solv" for repo https://conda.anaconda.org/conda-forge/noarch
info libmamba Expecting solv metadata : {"etag":"\"51fa274ca148416d4f1024a4356efb52\"","mod":"Wed, 05 Nov 2025 17:19:58 GMT","tool_version":"2.0_0.7.35","url":"https://conda.anaconda.org/conda-forge/noarch"}
info libmamba Loaded solv metadata : {"etag":"\"51fa274ca148416d4f1024a4356efb52\"","mod":"Wed, 05 Nov 2025 17:19:58 GMT","tool_version":"2.0_0.7.35","url":"https://conda.anaconda.org/conda-forge/noarch"}
info libmamba Metadata from solv are valid, loading successful
info libmamba Attempting to read libsolv solv file "/Users/pgunn/miniforge3/pkgs/cache/cfe2df73.solv" for repo https://conda.anaconda.org/conda-forge/osx-64
info libmamba Expecting solv metadata : {"etag":"\"4adb98ea76d677a55de018588c226d45\"","mod":"Wed, 05 Nov 2025 17:21:06 GMT","tool_version":"2.0_0.7.35","url":"https://conda.anaconda.org/conda-forge/osx-64"}
info libmamba Loaded solv metadata : {"etag":"\"4adb98ea76d677a55de018588c226d45\"","mod":"Wed, 05 Nov 2025 17:21:06 GMT","tool_version":"2.0_0.7.35","url":"https://conda.anaconda.org/conda-forge/osx-64"}
info libmamba Metadata from solv are valid, loading successful
info libmamba Attempting to read libsolv solv file "/Users/pgunn/miniforge3/pkgs/cache/20d9a1b0.solv" for repo https://conda.anaconda.org/flyem-forge/noarch
info libmamba Expecting solv metadata : {"etag":"","mod":"Wed, 22 Oct 2025 21:15:42 GMT","tool_version":"2.0_0.7.35","url":"https://conda.anaconda.org/flyem-forge/noarch"}
info libmamba Loaded solv metadata : {"etag":"","mod":"Wed, 22 Oct 2025 21:15:42 GMT","tool_version":"2.0_0.7.35","url":"https://conda.anaconda.org/flyem-forge/noarch"}
info libmamba Metadata from solv are valid, loading successful
info libmamba Attempting to read libsolv solv file "/Users/pgunn/miniforge3/pkgs/cache/630e7a55.solv" for repo https://conda.anaconda.org/flyem-forge/osx-64
info libmamba Expecting solv metadata : {"etag":"","mod":"Wed, 22 Oct 2025 21:15:42 GMT","tool_version":"2.0_0.7.35","url":"https://conda.anaconda.org/flyem-forge/osx-64"}
info libmamba Loaded solv metadata : {"etag":"","mod":"Wed, 22 Oct 2025 21:15:42 GMT","tool_version":"2.0_0.7.35","url":"https://conda.anaconda.org/flyem-forge/osx-64"}
info libmamba Metadata from solv are valid, loading successful
info libmamba Loading site packages
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