RMT Reference: Validation and Transitions

Validation declaratively blocks actions. Transitions describe the change between surface groups.

Syntax

Operator	Form	Allowed contexts	Parameters	Function	Diagnostics	Related operators
mode blocking	mode blocking	validation	mode blocking	Blocks target actions while fields are invalid.	Unknown modes are reported.	target action
target action	target action submit	validation	action reference	Selects which action is validated.	Target kind and reference must be present.	action
field	field app.email required email	validation	state path, rules	Declares a validated field.	Only known rules are allowed.	required, message
required	required	field	flag	Field must have a value.	Only valid in field.	message
email	email	field	flag	Field must have email shape.	Only valid in field.	pattern
minLength	minLength 3	field	number	Sets minimum length.	Value must follow.	maxLength
maxLength	maxLength 80	field	number	Sets maximum length.	Value must follow.	minLength
pattern	pattern "^[a-z]+$"	field	string	Declares a pattern contract.	Value must follow.	email
message	message "Enter email"	field	string	Provides a usable validation message.	Value must follow.	field
include	include shared.email	validation	validation reference	Includes another validation group.	Reference must exist.	validation
trigger action	trigger action submit	transition	action reference	Starts the surface change after an action.	Trigger kind must be present.	action
from surfaces	from surfaces [form]	transition	array or value	Declares outgoing surface group.	Value must parse.	to surfaces
to surfaces	to surfaces [done]	transition	array or value	Declares incoming surface group.	Value must parse.	from surfaces
use animation	use animation app.motion	transition	animation reference	Reuses a named AnimationEngine preset.	Reference must name an animation record.	animation
effect	effect slide-left	transition	effect name	Selects the visual change.	Unknown effects can be catalog diagnostics.	durationMs
durationMs	durationMs 220	transition	number	Sets duration in milliseconds.	Value must follow.	easing
easing	easing "ease-out"	transition	string	Sets CSS easing.	Value must follow.	effect
timeline	timeline enter then exit	transition	timeline mode	Declares enter/exit sequencing.	Unknown timeline modes are reported.	effect
layoutKey	layoutKey "card"	transition	stable key	Binds shared-element and layout-flip motion to a layout key.	Required for layout-aware effects.	shared-element, layout-flip
interrupt	interrupt replace	transition	cancel, finish or replace	Selects how a running transition is interrupted.	Unknown policies are reported.	trigger action
reducedMotion	reducedMotion fade	transition	instant, fade or none	Declares the fallback for reduced-motion hosts.	Unknown policies are reported.	durationMs
lane transition	lane transition	transition	lane name	Schedules the change on the transition lane.	Lane must exist or be cataloged.	lane

Allowed contexts

Validation clauses belong only in validation. Transition clauses belong only in transition.

Parameters

Validation fields point to state paths. Transitions point to surface identifiers and action triggers.

Description

Validation and transitions stay declarative so form flow and surface changes remain inspectable.

Examples

template reference.validation {
  state contact.email type string initial ""
  state app.status type object preserve {
    initial {
      text "Ready"
    }
  }

  action contact.next {
    input email string
    reduce state.app.status.text = "Next"
    emit contact.nextRequested with email input.email
  }

  validation contact.form {
    mode blocking
    target action contact.next
    field contact.email required email minLength 3 maxLength 80 pattern ".+@.+" message "Enter a valid email."
    include shared.email
  }

  animation contact.motion {
    effect fade
    durationMs 180
    reducedMotion fade
  }

  transition contact.toSummary {
    trigger action contact.next
    from surfaces [contact.form]
    to surfaces [contact.summary]
    use animation contact.motion
    effect slide-left
    durationMs 220
    easing "ease-out"
    timeline enter then exit
    layoutKey "contact-summary"
    interrupt replace
    reducedMotion fade
    lane transition
  }

  portal app.root root "#app" layer surface
  surface contact.form kind form component x-form {
    portal app.root
    lane user-blocking weight 85 {
      mount contact.form from endpoint contact.form
    }
  }
}

Diagnostics

Unknown field rules, missing action targets, incomplete transition targets and missing layoutKey values for layout-aware effects are reported.

Related operators

action, field, surface, lane, effect, payload, animation, use animation.

Related reading

The RMT reference index points from validation and transition records to their related expression forms. The AnimationEngine guide connects these operators to a complete AOT and runtime example. Related article