Migrating Classic Build Pipelines to YAML After March 2023 Deprecation

Goal: Determine whether existing classic build pipelines will continue to run after the announced September 2024 cutoff for classic pipeline creation and editing, and understand any differences between Azure DevOps Services and Azure DevOps Server.

The March 2023 update deprecated the classic UI editor, introduced a compatibility shim that permits existing pipelines to operate until the cutoff, and noted that the exact date may vary between the cloud service and on‑premises server. Organizations also need to consider that migration assistant output is advisory and that extensions relying on the classic pipeline API must adopt the new REST endpoints.

What is the precise date after which classic pipelines are blocked from execution in Azure DevOps Services? Does the cutoff differ for Azure DevOps Server, and if so, what is the Server‑specific timeline? After the cutoff, will existing classic pipelines continue to run until manually disabled, or will they be stopped automatically?