Use reconciliation branches when reverse-sync preview identity conflicts

General lesson: a protected-branch reverse sync may need a short-lived reconciliation branch when preview infrastructure keys ephemeral resources to the PR head branch. Create the branch from the target, merge the source with a regular two-parent merge, verify both parents and the final ancestry, and PR the reconciliation branch back to the target. This preserves release ancestry while giving preview systems an isolated branch identity. It applies to long-lived staging/production branches with per-PR database or deployment previews; it does not justify changing the repository's required merge strategy or bypassing failed checks.

A related failure mode occurs when merging the prerequisite PR triggers both push and pull-request CI on the same commit. Fixed local ports or other runner-scoped resources can collide between overlapping runs. Distinguish infrastructure collisions from code failures, wait for overlapping work to settle, and require a clean final run on the exact release head. A genuine code-quality failure still requires a separate fix and a fresh release-head validation.

Applies when: synchronizing long-lived release branches that use per-PR previews and overlapping push/PR CI. Keywords: release branch sync ancestry preview environment CI port collision reconciliation