Child workflows follow the same execution pattern as activities.

Serial Execution:

Using multiple yield statements ensures that each child workflow executes only after the previous one completes.

return [
    yield ChildWorkflowStub::make(MyChildWorkflow1::class),
    yield ChildWorkflowStub::make(MyChildWorkflow2::class),
    yield ChildWorkflowStub::make(MyChildWorkflow3::class),
];

Here, MyChildWorkflow1 must finish before MyChildWorkflow2 starts, and so on.

Parallel Execution:

Using ChildWorkflowStub::all() executes all child workflows concurrently and waits for all results before proceeding.

return yield ChildWorkflowStub::all([
    ChildWorkflowStub::make(MyChildWorkflow1::class),
    ChildWorkflowStub::make(MyChildWorkflow2::class),
    ChildWorkflowStub::make(MyChildWorkflow3::class),
]);

This approach is useful when child workflows don't have dependencies on each other.

Since child workflows mirror activity execution, you can mix and match these approaches, just like activities, to balance performance and dependencies.

Perfect, thank you.

I have one more question: how about compensation of parallel child workflow or activities? Because ChildWorkflowStub::all is an array, there is no option to define $this->compensate. Maybe Saga pattern should not be used with parallelism?

Thank you for help.

Saga pattern is only covered inside a workflow boundary.