As noted in our June 2025 release note, Drush 5 and 7 are no longer available on Pantheon, and pantheon.yml files retaining these retired values would eventually cause a git push to be rejected. That enforcement is now in effect.
Pantheon now rejects git push when drush_version is set to 5 or 7 in pantheon.yml. The supported values are 8, 9, and 10.
Validation runs whenever pantheon.yml changes are detected on push, including reverts. Sites with drush_version: 5 or 7 already committed are unaffected until the file is modified. A git revert or git reset that touches pantheon.yml will also trigger validation and be rejected if the retired values are present.
Action required
Customers with sites configured for Drush 5 or 7 should upgrade the Drush version in pantheon.yml to at least Drush 8:
Sites created with custom upstreams using these versions may also encounter errors on site creation or upstream updates if drush_version is still set to 5 or 7.