# Run.start()

The `.start()` method starts a workflow run with input data, allowing you to execute the workflow from the beginning.

## Usage example

```typescript
const run = await workflow.createRun();

const result = await run.start({
  inputData: {
    value: "initial data",
  },
});
```

## Parameters

**inputData?:** (`z.infer<TInput>`): Input data that matches the workflow's input schema

**requestContext?:** (`RequestContext`): Request Context data to use during workflow execution

**outputWriter?:** (`(chunk: TOutput) => Promise<void>`): Optional asynchronous function to handle output chunks as they are produced

**tracingContext?:** (`TracingContext`): currentSpan?:SpanCurrent span for creating child spans and adding metadata. Use this to create custom child spans or update span attributes during execution.

**tracingOptions?:** (`TracingOptions`): metadata?:Record\<string, any>Metadata to add to the root trace span. Useful for adding custom attributes like user IDs, session IDs, or feature flags.requestContextKeys?:string\[]Additional RequestContext keys to extract as metadata for this trace. Supports dot notation for nested values (e.g., 'user.id').traceId?:stringTrace ID to use for this execution (1-32 hexadecimal characters). If provided, this trace will be part of the specified trace.parentSpanId?:stringParent span ID to use for this execution (1-16 hexadecimal characters). If provided, the root span will be created as a child of this span.tags?:string\[]Tags to apply to this trace. String labels for categorizing and filtering traces.

**outputOptions?:** (`OutputOptions`): includeState?:booleanWhether to include the workflow run state in the result.

## Returns

**result:** (`Promise<WorkflowResult<TState, TOutput, TSteps>>`): A promise that resolves to the workflow execution result containing step outputs and status

**traceId?:** (`string`): The trace ID associated with this execution when Tracing is enabled. Use this to correlate logs and debug execution flow.

## Extended usage example

```typescript
import { RequestContext } from "@mastra/core/request-context";

const run = await workflow.createRun();

const requestContext = new RequestContext();
requestContext.set("variable", false);

const result = await run.start({
  inputData: {
    value: "initial data",
  },
  requestContext,
});
```

## Related

- [Workflows overview](https://mastra.ai/docs/workflows/overview)
- [Workflow.createRun()](https://mastra.ai/reference/workflows/workflow-methods/create-run)