Type Safety

Reflow tracks types through the entire workflow chain — most mistakes are compile errors, not runtime surprises.

• Workflow name is a string-literal type ('order-fulfillment', not string).
• Input is validated by your schema library and inferred at the type level.
• Step chaining — each step's prev is typed as the return value of the previous step.
• steps — typed access to every prior step's output by name.
• Engine — enqueue() only accepts registered workflow names with matching input.
• Test engine — run() returns typed step results keyed by step name.

// These are all compile-time errors:
engine.enqueue('typo', {})              // 'typo' is not a registered workflow
engine.enqueue('order-fulfillment', {}) // missing required input fields
workflow.step('x', async ({ prev }) => {
  prev.nonexistent                      // property doesn't exist on prev
})

How it flows

createWorkflow captures the name as a literal and the input type from your Standard Schema. Each .step() returns a new Workflow type that records the step's output, so the next handler's prev and the accumulated steps map stay accurate. createEngine collects the registered workflows into a map, which is what makes enqueue() reject unknown names and mismatched input.

Inference helpers

For building typed wrappers around Reflow, several helper types are exported — InferInput, InferSteps, WorkflowInputMap, WorkflowStepsMap, and the StepContext / StepConfig / EngineEvent types. See the Types reference.