YAML pipelines — quick notes

Fact	Detail
Hierarchy	pipeline → stages → jobs → steps
Job default order	parallel; `dependsOn` creates the graph/order
Stage default order	sequential
Agent-pool job	Steps run sequentially on one assigned agent; server jobs are agentless
Classic release pipelines	Job dependencies not supported; jobs run in sequence
Custom `condition`	replaces implicit `succeeded()`
`always()`	True after cancellation, but cannot run inside a skipped parent
Deployment strategies	`runOnce`, `rolling`, `canary`
`rolling`	VM-only; phases iterate per `maxParallel` batch, steps execute per VM target
Hook order	`preDeploy` → `deploy` → `routeTraffic` → `postRouteTraffic` → `on:`
`template:`	Composes by inserting content
`extends:`	Constrains consumer structure
Enforcement	Required template check on a protected resource enforces `extends:` adoption
Template parameter types	`string`, `number`, `boolean`, `object`, `step`/`stepList`, `job`/`jobList`, `deployment`/`deploymentList`, `stage`/`stageList`; no `stringList` in templates

Traps

“Jobs run top to bottom” is false in YAML but true in classic release.
always() survives cancellation only within a parent that is scheduled.
Rolling has three batches for six VMs at two per batch, but a per-VM step runs six times.
Bare extends: constrains a consumer that uses it; the protected-resource check enforces use.

Primary sources