`nodefaults` channels take forever to "download" even though they should be the fastest

[corneliusroemer]

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?

Micromamba

Search tried in issue tracker

nodefaults

Latest version of Mamba

• My problem is not solved with the latest version

Tried in Conda?

I didn't try

Describe your issue

I use nodefaults in my channel list to ensure that I don't use the default anaconda channels (see https://docs.conda.io/projects/conda/en/4.6.1/user-guide/tasks/manage-environments.html#creating-an-environment-file-manually)

nodefaults should just be a sentinel - a sign for micromamba to not load defaults. It should be seamless.

Yet, it can sometimes take dozens of seconds to download the "nodefaults" - that makes no sense. It should be the fastest of all channel indexes to load.

$ micromamba update --all
bioconda/osx-arm64                                 357.3kB @ 226.2kB/s  0.1s
bioconda/noarch                                      5.0MB @  18.9MB/s  0.2s
conda-forge/osx-arm64                               18.7MB @  30.1MB/s  0.6s
conda-forge/noarch                                  23.1MB @  34.4MB/s  0.6s
nodefaults/osx-arm64                               125.0 B @ 132.0 B/s  0.9s
nodefaults/noarch                                  116.0 B @   3.0 B/s 35.2s

mamba info / micromamba info

micromamba info

       libmamba version : 2.3.3
     micromamba version : 2.3.3
           curl version : libcurl/8.14.1 (OpenSSL/3.5.4) SecureTransport 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 bz2lib/1.0.8 libzstd/1.5.7 CommonCrypto/system libb2/bundled
       envs directories : /Users/cr/micromamba/envs
          package cache : /Users/cr/micromamba/pkgs
                          /Users/cr/.mamba/pkgs
            environment : base
           env location : /Users/cr/micromamba
      user config files : /Users/cr/.mambarc
 populated config files : /Users/cr/.mambarc
                          /Users/cr/.condarc
       virtual packages : __unix=0=0
                          __osx=26.0.1=0
                          __archspec=1=arm64
               channels : https://conda.anaconda.org/conda-forge/noarch
                          https://conda.anaconda.org/conda-forge/osx-arm64
                          https://conda.anaconda.org/bioconda/noarch
                          https://conda.anaconda.org/bioconda/osx-arm64
                          https://conda.anaconda.org/nodefaults/noarch
                          https://conda.anaconda.org/nodefaults/osx-arm64
       base environment : /Users/cr/micromamba
               platform : osx-arm64

Logs

environment.yml

~/.condarc

# .mambarc

repodata_use_zst: true
always_yes: false
show_channel_urls: true
solver: libmamba
changeps1: False
channels:
  - conda-forge
  - bioconda
  - nodefaults
channel_priority: strict


---
# .condarc

always_yes: true
show_channel_urls: true
solver: libmamba