Lesson Plan Children

LessonPlan is the only current parent modality. It implements the HasChildren trait, managing child whiteboard sessions via the Slot container.

HasChildren

impl HasChildren for LessonPlan {
    type ChildModality = Whiteboard;
    type ChildSessionIntent = SessionIntent<WhiteboardIntent>;

    fn children(&self) -> &HashMap<String, Slot<
        Session<Whiteboard, SessionIntent<WhiteboardIntent>>,
        Vec<WhiteboardElement>,
    >> { &self.children }

    fn children_mut(&mut self) -> &mut HashMap<...> { &mut self.children }

    fn selected_child_id(&self) -> Option<&str> {
        // returns the currently focused slide ID
    }

    fn reconcile_children(&mut self) {
        // create Cold slots for new placements, remove stale ones
    }
}

reconcile_children() is called inside the ReduceIntent impl after modality reduce, before the lifecycle runs.

Hot/Cold Lifecycle

All children start Cold when the session opens. The Slot enum manages the transition:

pub enum Slot<C, O> {
    Cold(O),    // cached compiled output, no recompilation
    Hot(C),     // full component (Session), can recompile
}

Lifecycle Steps

1. Open — all children start Cold (cached output from parent’s synced state or empty).
2. Navigate — Dart dispatches ParentSessionIntent::WarmChild { id }.
3. Load — WarmChild spawns fx.spawn(backend.load) which returns ParentSessionFeedback::ChildWarmed { id, bytes }.
4. Hot — a full Session<Whiteboard, SessionIntent<WhiteboardIntent>> is created from the loaded bytes and inserted into the slot.
5. Dispatch — child intents arrive via ParentSessionIntent::Child { id, intent }, which calls child_session.dispatch().
6. Close — session persists children internally (Hot sessions export their docs).

Dispatching to a Cold slot is an error — the child must be warmed first.

Child AI Subagents

Each Hot child session has its own SessionEphemeral (its own AI state). During AI generation:

1. Parent warms child: WarmChild { id } —> backend load —> ChildWarmed
2. Parent dispatches to child: Child { id, intent: SessionIntent::Ai(SendMessage) }
3. Child runs its own reduce cycle independently
4. Parent recompiles after child completes

Related

• Overview — struct, types, compilation, parent dispatch
• Whiteboard — the child modality embedded in each slide
• Slot — the hot/cold container
• Children — session-level children reference