> ## Documentation Index
> Fetch the complete documentation index at: https://docs.definable.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Running Workflows

> Execute workflows and access step results.

## Basic Execution

```python theme={null}
result = await workflow.arun("Research AI trends")

result.content       # Final step's content
result.success       # True if all steps succeeded
result.duration_ms   # Total execution time
result.step_outputs  # List[StepOutput] for each step
```

<Note>
  `Workflow.arun()` returns a `WorkflowOutput`, which is different from `RunOutput`. It includes step-level results.
</Note>

## Accessing Step Results

```python theme={null}
# By name
research = result.get_step_output("researcher")
print(research.content)
print(research.duration_ms)

# Iterate all steps
for step_output in result.step_outputs:
    print(f"{step_output.step_name}: {step_output.duration_ms:.0f}ms")
```

## Step Context

Each step receives a `StepInput` with context from previous steps:

```python theme={null}
from definable.agent.workflow import StepInput

async def custom_step(ctx: StepInput):
    original = ctx.input                         # Original workflow input
    prev = ctx.get_last_step_content()           # Previous step's output
    research = ctx.get_step_content("researcher")  # Specific step by name
    api_key = ctx.session_state.get("api_key")   # Shared session state
    return f"Processed: {research}"
```

## Session State

Share data across steps:

```python theme={null}
workflow = Workflow(
    name="stateful",
    steps=[...],
    session_state={"api_key": "...", "mode": "production"},
)

# Override per-run
result = await workflow.arun("Go", session_state={"mode": "staging"})
```

## Events

| Event                       | When                        |
| --------------------------- | --------------------------- |
| `WorkflowRunStartedEvent`   | Workflow begins             |
| `WorkflowRunCompletedEvent` | Workflow completes          |
| `WorkflowRunErrorEvent`     | Workflow fails              |
| `StepStartedEvent`          | A step begins               |
| `StepCompletedEvent`        | A step completes            |
| `StepErrorEvent`            | A step fails                |
| `StepSkippedEvent`          | A step is skipped           |
| `LoopIterationEvent`        | Loop completes an iteration |

```python theme={null}
from definable.agent.workflow import StepCompletedEvent

workflow.events.on(StepCompletedEvent, lambda e: print(f"{e.step_name}: {e.duration_ms:.0f}ms"))
```

## Imports

```python theme={null}
from definable.agent.workflow import (
    Workflow, Step, Steps, Parallel, Loop, Condition, Router,
    StepInput, StepOutput, WorkflowOutput,
)
```