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.
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.
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.
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 string in place of a function. The expression must evaluate to a step name from choices.

Selector Function Signatures

Basic Signature

def selector(step_input: StepInput) -> Union[str, Step, List[Step]]:
    ...

Extended Signature (with step_choices)

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)

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:

async def selector(step_input: StepInput, step_choices: list) -> Union[str, Step, List[Step]]:
    ...