Concepts & architecture

A workflow describes a unit of work: tasks, transitions, inputs and outputs.

In Quarkus Flow, workflows are defined using the CNCF Workflow Java DSL and exposed as CDI beans.

A Flow is a CDI bean that provides a descriptor() method returning a Workflow.

At build time, Quarkus Flow discovers all Flow beans and generates compiled workflow definitions.

A workflow definition is the compiled representation used at runtime.

A workflow instance is a running execution of that definition with its own data (context) and lifecycle (created, running, completed, failed).

Quarkus scans for Flow beans or YAML definitions.

For each one, it compiles the Java/YAML DSL into a WorkflowDefinition.

The definitions are registered for injection and use at runtime.

Your application code starts instances from injected Flows or definitions.

The engine executes tasks, transitions, and event waits.

Results and errors are exposed through a simple API (as(…​), etc.).

Use HTTP/OpenAPI tasks to call external services from workflows.

See Call HTTP and OpenAPI services.

Integrate with MicroProfile Reactive Messaging to consume and emit CloudEvents.

See Use messaging and events.

Orchestrate AI agents built with LangChain4j as tasks in your workflows.

See Agentic workflows with LangChain4j.