diff --git a/.github/scripts/test.sh b/.github/scripts/test.sh
index 1fdc349e8..77500cd46 100755
--- a/.github/scripts/test.sh
+++ b/.github/scripts/test.sh
@@ -6,11 +6,11 @@ run_tests() {
   echo TESTING PYTHON $PYTHON_VERSION
   env=python-$PYTHON_VERSION
   devpkgs=$(jq .packages.dev[] recipe/meta.json | tr -d ' "')
-  conda create --yes --name $env --quiet python=$PYTHON_VERSION $devpkgs
+  conda create --yes --name $env --quiet $devpkgs
   conda activate $env
+  conda install --yes python=$PYTHON_VERSION
   . notebooks/install-deps
   set -x
-  python --version
   git clean -dfx
   pip install --editable src # sets new Python version in entry-point scripts
   make test && make test-nb
diff --git a/recipe/meta.json b/recipe/meta.json
index 73b1e8a5a..e69d64c76 100644
--- a/recipe/meta.json
+++ b/recipe/meta.json
@@ -8,19 +8,19 @@
       "docformatter ==1.7.*",
       "f90nml ==1.4.*",
       "iotaa ==1.1.*",
-      "isort ==5.13.*",
+      "isort ==6.0.*",
       "jinja2 ==3.1.*",
       "jq ==1.7.*",
       "jsonschema >=4.18,<4.24",
-      "lxml ==5.3.*",
+      "lxml ==5.2.*",
       "make ==4.4.*",
-      "mypy ==1.14.*",
+      "mypy ==1.15.*",
       "pip",
       "pylint ==3.3.*",
       "pytest ==8.3.*",
       "pytest-cov ==6.0.*",
       "pytest-xdist ==3.6.*",
-      "python >=3.9,<3.13",
+      "python <3.13,==3.9,>=3.9",
       "pyyaml ==6.0.*",
       "requests ==2.32.*",
       "setuptools"
@@ -30,7 +30,7 @@
       "iotaa ==1.1.*",
       "jinja2 ==3.1.*",
       "jsonschema >=4.18,<4.24",
-      "lxml ==5.3.*",
+      "lxml ==5.2.*",
       "python >=3.9,<3.13",
       "pyyaml ==6.0.*",
       "requests ==2.32.*"
diff --git a/recipe/meta.yaml b/recipe/meta.yaml
index 0f8b60a1d..dab5c3850 100644
--- a/recipe/meta.yaml
+++ b/recipe/meta.yaml
@@ -1,4 +1,5 @@
 {% set info = load_file_data("uwtools/resources/info.json") %}
+{% set pymin = "3.9" %}
 
 package:
   name: uwtools
@@ -10,29 +11,31 @@ build:
   noarch: python
   number: {{ info["buildnum"] }}
 requirements:
-  build:
+  host:
     - pip
+    - python {{ pymin }}
     - setuptools
   run:
     - f90nml 1.4.*
     - iotaa 1.1.*
     - jinja2 3.1.*
     - jsonschema >=4.18,<4.24
-    - lxml 5.3.*
-    - python >=3.9,<3.13
+    - lxml 5.2.*
+    - python >={{ pymin }},<3.13
     - pyyaml 6.0.*
     - requests 2.32.*
 test:
   requires:
     - black 24.10.*
     - docformatter 1.7.*
-    - isort 5.13.*
+    - isort 6.0.*
     - jq 1.7.*
     - make 4.4.*
-    - mypy 1.14.*
+    - mypy 1.15.*
     - pylint 3.3.*
     - pytest 8.3.*
     - pytest-cov 6.0.*
     - pytest-xdist 3.6.*
+    - python {{ pymin }}
 about:
   license: LGPL
diff --git a/recipe/run_test.sh b/recipe/run_test.sh
index 17bd3b8e1..15079fdb1 100755
--- a/recipe/run_test.sh
+++ b/recipe/run_test.sh
@@ -51,6 +51,7 @@ unittest() {
 }
 
 test "${CONDA_BUILD:-}" = 1 && cd ../test_files || cd $(dirname $0)/../src
+python --version
 if [[ -n "${1:-}" ]]; then
   # Run single specified code-quality tool.
   $1