diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 619c1b25..22d356e6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,7 +19,7 @@ jobs:
             TARGET_PLATFORM: osx-arm64
             OS_NAME: "MacOSX"
 
-          - os: macos-latest
+          - os: macos-13  # Force Intel
             ARCH: x86_64
             TARGET_PLATFORM: osx-64
             OS_NAME: "MacOSX"
diff --git a/Miniforge3/construct.yaml b/Miniforge3/construct.yaml
index f6b596bf..fbdd2659 100644
--- a/Miniforge3/construct.yaml
+++ b/Miniforge3/construct.yaml
@@ -1,5 +1,5 @@
-{% set version = os.environ.get("MINIFORGE_VERSION", "25.3.0-3") %}
-{% set conda_libmamba_solver_version = "25.3.0" %}
+{% set version = os.environ.get("MINIFORGE_VERSION", "25.5.1-1") %}
+{% set conda_libmamba_solver_version = "25.4.0" %}
 # This file is parsed by the scripts to define
 #   - `MICROMAMBA_VERSION` in `scripts/build.sh`
 #   - `MAMBA_VERSION` in `scripts/test.sh`
@@ -16,6 +16,11 @@ channels:
   - conda-forge
 
 write_condarc: True
+condarc: |
+  channels:
+    - conda-forge
+  default_activation_env: default-env
+
 # keep pkgs for space-saving implications for hardlinks when create new environments
 # and keep the same with Miniconda
 keep_pkgs: True
@@ -36,12 +41,18 @@ user_requested_specs:
 
 specs:
   - python 3.12.*
-  - conda {{ version.split("-")[0] }}
-  - mamba {{ mamba_version }}
+  - conda {{ version.split("-")[0] }}.*
+  - mamba {{ mamba_version }}.*
   - conda-libmamba-solver {{ conda_libmamba_solver_version }}
   - pip
   - miniforge_console_shortcut 1.*  # [win]
 
+extra_envs:
+  default-env:
+    specs:
+      - python 3.12.*
+      - pip
+
 virtual_specs:
   - __glibc >=2.17 # [linux]
   - __osx >=10.13 # [osx]
diff --git a/scripts/test.sh b/scripts/test.sh
index 34858827..86d7ed5a 100755
--- a/scripts/test.sh
+++ b/scripts/test.sh
@@ -29,22 +29,26 @@ if [[ "$(uname)" == MINGW* ]]; then
 
   echo "***** Setup conda *****"
   # Workaround a conda bug where it uses Unix style separators, but MinGW doesn't understand them
+  # we need condabin in PATH for both conda and mamba
   export PATH=$CONDA_PATH/Library/bin:$PATH
   # shellcheck disable=SC1091
-  source "${CONDA_PATH}/Scripts/activate"
-  conda.exe config --set show_channel_urls true
+  eval "$("$CONDA_PATH/python.exe" -m conda shell.posix hook)"
+  eval "$("$CONDA_PATH/Library/bin/mamba.exe" shell hook)"
+  conda config --set show_channel_urls true
 
   echo "***** Print conda info *****"
-  conda.exe info
-  conda.exe list
+  conda info
+  conda list
+  conda info --envs
+  conda config --show-sources
 
   echo "***** Check if we are bundling packages from msys2 or defaults *****"
-  conda.exe list | grep defaults && exit 1
-  conda.exe list | grep msys2 && exit 1
+  conda list | grep defaults && exit 1
+  conda list | grep msys2 && exit 1
 
   echo "***** Check if we can install a package which requires msys2 *****"
-  conda.exe install r-base --yes --quiet
-  conda.exe list
+  conda install r-base --yes --quiet
+  conda list
 else
   # Test one of our installers in batch mode
   if [[ "${INSTALLER_NAME}" == "Miniforge3" ]]; then
@@ -66,13 +70,18 @@ EOF
 
   echo "***** Setup conda *****"
   # shellcheck disable=SC1091
-  source "${CONDA_PATH}/bin/activate"
+  eval "$("$CONDA_PATH/bin/python" -m conda shell.posix hook)"
+  eval "$("$CONDA_PATH/bin/mamba" shell hook)"
 
   echo "***** Print conda info *****"
   conda info
   conda list
+  conda info --envs
+  conda config --show-sources
 fi
 
+set +x
+
 echo "+ Mamba does not warn (check that there is no warning on stderr) and returns exit code 0"
 mamba --help 2> stderr.log || cat stderr.log
 test ! -s stderr.log
@@ -96,7 +105,13 @@ echo "+ Testing mamba channels"
 mamba info --json | python -c "import sys, json; info = json.loads(sys.stdin.read()); assert any('${MINIFORGE_CHANNEL_NAME}' in c for c in info['channels']), info"
 echo "  OK"
 
+set -x
+
 echo "***** Python path *****"
+# These tests use Python, which does need an active environment
+
+conda activate
+
 python -c "import sys; print(sys.executable)"
 python -c "import sys; assert 'miniforge' in sys.executable"
 
@@ -107,6 +122,29 @@ python -c "import platform; print(platform.system())"
 python -c "import platform; print(platform.machine())"
 python -c "import platform; print(platform.release())"
 
+conda deactivate
+
+echo "***** Check default environment *****"
+
+conda activate
+default_prefix_nameless="$CONDA_PREFIX"
+echo "default_prefix_nameless=$default_prefix_nameless"
+default_python_nameless="$(type python)"
+echo "default_python_nameless=$default_python_nameless"
+python -V
+conda deactivate
+
+conda activate default-env
+default_prefix="$CONDA_PREFIX"
+echo "default_prefix=$default_prefix"
+default_python="$(type python)"
+echo "default_python=$default_python"
+python -V
+conda deactivate
+
+test "$default_prefix_nameless" = "$default_prefix"
+test "$default_python_nameless" = "$default_python"
+
 echo "***** Done: Testing installer *****"
 
 echo "***** Testing the usage of mamba main commands *****"