diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 5ce5aed..2d0b647 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -19,7 +19,11 @@ pypi-twine:
     - tags
   script:
     - pip install --upgrade pip
-    - pip install twine
+    # Pin twine <6 — newer twine auto-detects GitLab CI and refuses to
+    # fall back to ~/.pypirc on the runner, requiring PYPI_ID_TOKEN
+    # (Trusted Publishing OIDC). Until we migrate to Trusted Publishing,
+    # stick with the classic ~/.pypirc auth on the build runner.
+    - pip install "twine<6"
     - python3 setup.py sdist bdist_wheel
     - twine check dist/*
     - twine upload --non-interactive dist/*