Use default latest Python for extra sessions

.github/workflows/test.yml

@@ -41,7 +41,6 @@ jobs:
     runs-on: ${{ matrix.os }}
     continue-on-error: true
     env:
-      NOXPYTHON: ${{ matrix.python-version }}
       NOXSESSION: ${{ matrix.session }}
     strategy:
       fail-fast: false
@@ -57,17 +56,18 @@ jobs:
         - "3.13"
         sqlalchemy: ["2"]
         include:
-        - { session: tests,   python-version: "3.13", os: "ubuntu-latest", sqlalchemy: "1" }
-        - { session: doctest, python-version: "3.13", os: "ubuntu-latest", sqlalchemy: "2" }
-        - { session: mypy,    python-version: "3.12",  os: "ubuntu-latest", sqlalchemy: "2" }
-        - { session: deps,    python-version: "3.12",  os: "ubuntu-latest", sqlalchemy: "2" }
+        - { session: tests,   python-version: "3.x", os: "ubuntu-latest", sqlalchemy: "1" }
+        - { session: doctest, python-version: "3.x", os: "ubuntu-latest", sqlalchemy: "2" }
+        - { session: mypy,    python-version: "3.x",  os: "ubuntu-latest", sqlalchemy: "2" }
+        - { session: deps,    python-version: "3.x",  os: "ubuntu-latest", sqlalchemy: "2" }
 
     steps:
     - uses: actions/checkout@v4
       with:
         fetch-depth: 0
 
     - uses: actions/setup-python@v5
+      id: setup-python
       with:
         python-version: ${{ matrix.python-version }}
         allow-prereleases: true
@@ -94,6 +94,7 @@ jobs:
 
     - name: Run Nox
       env:
+        NOXPYTHON: ${{ steps.setup-python.outputs.python-version }}
         SQLALCHEMY_VERSION: ${{ matrix.sqlalchemy }}
         PIP_PRE: "1"
         UV_PRERELEASE: allow

noxfile.py

@@ -32,7 +32,7 @@
     "3.9",
     "3.8",
 ]
-main_python_version = "3.12"
+main_python_version = "3.13"
 locations = "singer_sdk", "tests", "noxfile.py", "docs/conf.py"
 nox.options.sessions = (
     "mypy",