Rule 1 of 8 · Chapter I — Pipeline Design
Pipelines live in YAML, beside the code they build.
Why this rule exists
Classic UI pipelines cannot be reviewed, diffed, reverted, or copied to the next project. The pipeline is code; treat it with the same version control as everything else it builds.
In practice
azure-pipelines.yml at the repo root, changed via pull request like any other file. UI edits are for reading, not writing.