> ## Documentation Index
> Fetch the complete documentation index at: https://agno-v2-docs-scavio-google-v2.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Router Steps

> Constructor parameters for the workflow Router class, which dynamically selects steps to execute.

## Parameters

| Parameter                   | Type                                                                    | Default         | Description                                                                                                                       |
| --------------------------- | ----------------------------------------------------------------------- | --------------- | --------------------------------------------------------------------------------------------------------------------------------- |
| `selector`                  | `Callable[[StepInput], ...] \| Callable[[StepInput, list], ...] \| str` | `None`          | Function or CEL expression string to select steps dynamically. Functions can optionally accept `step_choices` as second parameter |
| `choices`                   | `WorkflowSteps`                                                         | Required        | Available steps for selection. Supports nested lists (becomes Steps container)                                                    |
| `name`                      | `Optional[str]`                                                         | `None`          | Name of the router step                                                                                                           |
| `description`               | `Optional[str]`                                                         | `None`          | Description of the router step                                                                                                    |
| `human_review`              | `Optional[HumanReview]`                                                 | `None`          | All HITL settings in a single config. See [HumanReview Config](/workflows/hitl/human-review).                                     |
| `requires_confirmation`     | `bool`                                                                  | `False`         | Pause for user confirmation before executing selected route                                                                       |
| `confirmation_message`      | `Optional[str]`                                                         | `None`          | Message shown to user when requesting confirmation                                                                                |
| `requires_user_input`       | `bool`                                                                  | `False`         | Pause for user to select route(s) instead of using selector. See [Router HITL](/workflows/hitl/router#user-selection).            |
| `user_input_message`        | `Optional[str]`                                                         | `None`          | Message shown to user when requesting route selection                                                                             |
| `allow_multiple_selections` | `bool`                                                                  | `False`         | Allow user to select multiple routes                                                                                              |
| `user_input_schema`         | `Optional[List[Dict[str, Any]]]`                                        | `None`          | Custom input schema for the user-input pause. If unset, the pause presents the available `choices` for route selection            |
| `requires_output_review`    | `bool`                                                                  | `False`         | Pause after the selected route completes to review its output. See [Output Review](/workflows/hitl/output-review).                |
| `output_review_message`     | `Optional[str]`                                                         | `None`          | Message shown to user during output review                                                                                        |
| `hitl_max_retries`          | `int`                                                                   | `3`             | Max re-executions when an output review is rejected with `OnReject.retry`                                                         |
| `on_reject`                 | `Union[OnReject, str]`                                                  | `OnReject.skip` | Action when rejected: `skip`, `cancel`, `retry`                                                                                   |

## Selector Return Types

The selector function can return any of the following:

| Return Type  | Description                                           |
| ------------ | ----------------------------------------------------- |
| `str`        | Step name as string - Router resolves it from choices |
| `Step`       | Step object directly                                  |
| `List[Step]` | List of steps for chaining execution                  |

`selector` also accepts a [CEL expression](/examples/workflows/cel-expressions/router/cel-ternary) string in place of a function. The expression must evaluate to a step name from `choices`.

## Selector Function Signatures

### Basic Signature

```python theme={null}
def selector(step_input: StepInput) -> Union[str, Step, List[Step]]:
    ...
```

### Extended Signature (with step\_choices)

```python theme={null}
def selector(step_input: StepInput, step_choices: list) -> Union[str, Step, List[Step]]:
    ...
```

The `step_choices` parameter provides access to the prepared Step objects from `Router.choices`, enabling dynamic selection based on available options.

### Extended Signature (with session\_state)

```python theme={null}
def selector(step_input: StepInput, session_state: dict) -> Union[str, Step, List[Step]]:
    ...
```

If the selector accepts a `session_state` parameter, the workflow's session state is passed to it at call time.

### Async Support

All selector signatures support async functions:

```python theme={null}
async def selector(step_input: StepInput, step_choices: list) -> Union[str, Step, List[Step]]:
    ...
```