Vyuh Workflow Engine

Business Process Orchestration

A powerful, extensible workflow engine for Dart and Flutter applications. Build complex business processes, approval flows, and stateful automations with a clean, composable API.

Why Workflow Engine?

Visual Process Modeling

Define workflows using a fluent builder API with support for sequences, parallels, and gateways.

Human-in-the-Loop

Built-in support for user tasks, approvals, and signal-based interactions.

Persistent State

Pluggable storage adapters for reliable workflow state persistence and recovery.

Fully Extensible

Type registries for custom task executors, conditions, signals, and more.

Getting Started

InstallationAdd to your Dart or Flutter project

Quick StartBuild your first workflow

ArchitectureUnderstand the engine design

Core Concepts

• Workflow — The blueprint for your business process
• Workflow Instance — A running execution of a workflow
• Workflow Descriptor — Register executors with the engine
• Tokens — Track execution position through the graph
• Data Flow — How data moves through your workflow
• Type Registries — Extend the engine with custom executors

Node Types

Node	Purpose
Start/End	Entry and exit points
Task	Automated tasks
User Task	Human interactions
Signal Wait	Wait for external events
Gateways	Branching and merging

Patterns & Examples

Control FlowBranching, looping, and parallel executionApprovalsMulti-level approval workflowsError HandlingCompensation and retry strategiesSimple ApprovalBasic approval workflow exampleParallel TasksConcurrent task execution

Quick Example

// Create deserialization context and engine
final context = RegistryDeserializationContext(
  descriptors: [DefaultWorkflowDescriptor()],
);
final engine = WorkflowEngine(
  context: context,
  storage: InMemoryStorage(context: context),
);
await engine.initialize();

// Define a simple approval workflow
final workflow = WorkflowBuilder('expense-approval', 'Expense Approval')
    .start('begin')
    .task('validate-expense', execute: (ctx) async {
      return {'valid': true};
    })
    .userTask('manager-review',
        signal: 'approval_decision',
        schemaType: 'approvalTask',
        assignToRole: 'managers',
        storeAs: 'approvalResult')
    .oneOf('decision', [
      Branch.whenTrue('approvalResult.approved', then: 'process-payment'),
      Branch.otherwise(then: 'notify-rejection'),
    ])
    .task('process-payment', execute: (ctx) async {
      return {'processed': true};
    })
    .end('completed')
    .from('decision').to('notify-rejection')
    .task('notify-rejection', execute: (ctx) async {
      return {'notified': true};
    })
    .end('rejected')
    .build();

// Register and start the workflow
engine.registerWorkflow(workflow);
final instance = await engine.startWorkflow(
  workflowCode: workflow.code,
  input: {'amount': 500, 'description': 'Conference travel'},
);