refactor(core): make KlondikeInstruction the move currency

Remove the (from, to, count) tuple as an internal move-passing wrapper.
Game logic now stays in KlondikeInstruction space end to end:

- Add GameState::apply_instruction, the native apply path. move_cards
  becomes a thin pile-coordinate adapter that converts to an instruction
  and delegates, so move bookkeeping (validation, score/recycle history,
  undo snapshot) lives in one place instead of being duplicated.
- next_auto_complete_move matches DstFoundation directly instead of
  projecting every candidate to pile coordinates.
- proptests and the storage round-trip test apply instructions directly
  rather than round-tripping instruction -> tuple -> move_cards.

The single instruction -> pile decode is renamed instruction_to_highlight
-> instruction_to_piles and kept in core: decoding a tableau run length
needs upstream pile-stack types core does not re-export, so relocating it
would duplicate the logic across engine and wasm. The two rendering edges
(engine hint highlight, wasm debug move list) call this one decoder; the
engine's hint_piles is a thin delegation to it.

Also includes the CardEntityIndex render-side index and a SelectionPlugin
init_resource fix so update_selection_highlight no longer panics in test
harnesses that omit CardPlugin.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

solitaire_core/src/game_state.rs

@@ -826,14 +826,24 @@ impl GameState {
         }
     }
 
-    /// Converts an upstream [`KlondikeInstruction`] into the engine's
+    /// Decodes an upstream [`KlondikeInstruction`] into the `(from, to, count)`
-    /// `(from, to, count)` pile-move form, resolving multi-card tableau moves
+    /// pile coordinates of `solitaire_core`'s own pile model, against the live
-    /// against the live board. Returns `None` for no-op instructions
+    /// board. Returns `None` for no-op instructions (foundation→foundation, or a
-    /// (foundation→foundation, or a tableau move of zero cards).
+    /// tableau move of zero cards).
     ///
-    /// Used by the hint system to render a solver's recommended first move,
+    /// This is the single, canonical translation from the upstream instruction
-    /// and internally by [`Self::possible_instructions`].
+    /// move-currency to core's [`KlondikePile`] vocabulary. It lives in core
-    pub fn instruction_to_move(
+    /// because decoding a tableau-run length requires upstream pile-stack types
+    /// (`KlondikePileStack`/`SkipCards`) that the engine and wasm crates do not
+    /// see — relocating it would duplicate this logic across both crates. The
+    /// two edges that genuinely need on-screen positions call it: the engine's
+    /// hint highlight (which pile to glow) and the wasm debug move list (pile
+    /// names + run length serialized to the browser harness).
+    ///
+    /// Game logic — auto-complete, move application, the property tests — stays
+    /// in instruction space and never calls this; applying a move uses
+    /// [`Self::apply_instruction`].
+    pub fn instruction_to_piles(
         &self,
         instruction: KlondikeInstruction,
     ) -> Option<(KlondikePile, KlondikePile, usize)> {
@@ -931,6 +941,28 @@ impl GameState {
         }
 
         let instruction = self.instruction_for_move(from, to, count)?;
+        self.apply_instruction(instruction)
+    }
+
+    /// Apply an upstream [`KlondikeInstruction`] directly to the live session.
+    ///
+    /// This is the native apply path for moves that already exist in
+    /// instruction form — solver hints, auto-complete, replay, and the property
+    /// tests. User drag-and-drop enters through [`Self::move_cards`], which is a
+    /// thin adapter that converts pile coordinates to an instruction and
+    /// delegates here, so the move bookkeeping (rule validation, score history,
+    /// recycle accounting, undo snapshot) lives in exactly one place.
+    ///
+    /// Returns [`MoveError::RuleViolation`] if the instruction is illegal in the
+    /// current position, or [`MoveError::GameAlreadyWon`] once the game is over.
+    pub fn apply_instruction(
+        &mut self,
+        instruction: KlondikeInstruction,
+    ) -> Result<(), MoveError> {
+        if self.is_won() {
+            return Err(MoveError::GameAlreadyWon);
+        }
+
         let config = self.validation_config();
         if !self
             .session
@@ -941,12 +973,16 @@ impl GameState {
             return Err(MoveError::RuleViolation("move violates rules".into()));
         }
 
-        let (score_delta, _) = self.pre_instruction_score_delta(instruction);
+        let (score_delta, is_recycle) = self.pre_instruction_score_delta(instruction);
 
         self.score_history.push(self.score);
-        self.is_recycle_history.push(false);
+        self.is_recycle_history.push(is_recycle);
 
         self.session.process_instruction(instruction);
+
+        if is_recycle {
+            self.recycle_count = self.recycle_count.saturating_add(1);
+        }
         self.score = (self.score + score_delta).max(0);
         Ok(())
     }
@@ -996,8 +1032,13 @@ impl GameState {
         self.session.state().state().is_win_trivial()
     }
 
-    /// Returns all currently valid `(from, to, count)` moves.
+    /// Returns all currently valid moves as upstream [`KlondikeInstruction`]s,
-    pub fn possible_instructions(&self) -> Vec<(KlondikePile, KlondikePile, usize)> {
+    /// ordered by the `klondike` solver's move priority.
+    ///
+    /// This is the engine's move currency. Callers that need on-screen pile
+    /// positions — hint highlighting and the wasm debug move list — decode each
+    /// instruction with [`Self::instruction_to_piles`] at their UI edge.
+    pub fn possible_instructions(&self) -> Vec<KlondikeInstruction> {
         if self.is_won() {
             return Vec::new();
         }
@@ -1008,7 +1049,6 @@ impl GameState {
             .state()
             .get_sorted_moves(&config)
             .into_iter()
-            .filter_map(|instruction| self.instruction_to_move(instruction))
             .collect()
     }
 
@@ -1061,20 +1101,20 @@ impl GameState {
             return None;
         }
 
+        // A foundation-bound single-card move is exactly a `DstFoundation`
+        // instruction whose source is not itself a foundation. Match the
+        // instruction variant directly rather than projecting every candidate
+        // to `(from, to, count)` pile coordinates — auto-complete is pure game
+        // logic and never needs on-screen positions.
         self.possible_instructions()
             .into_iter()
-            .find_map(|(from, to, count)| {
+            .find_map(|instruction| match instruction {
-                if count != 1 {
+                KlondikeInstruction::DstFoundation(dst)
-                    return None;
+                    if !matches!(dst.src, KlondikePile::Foundation(_)) =>
-                }
+                {
-                if matches!(from, KlondikePile::Foundation(_)) {
+                    Some((dst.src, KlondikePile::Foundation(dst.foundation)))
-                    return None;
-                }
-                if matches!(to, KlondikePile::Foundation(_)) {
-                    Some((from, to))
-                } else {
-                    None
                 }
+                _ => None,
             })
     }
 
@@ -1098,6 +1138,16 @@ impl GameState {
 mod tests {
     use super::*;
 
+    /// Resolve every legal instruction to its `(from, to, count)` piles for
+    /// tests that assert against pile positions. Mirrors what a UI edge does
+    /// via [`GameState::instruction_to_piles`].
+    fn legal_pile_moves(game: &GameState) -> Vec<(KlondikePile, KlondikePile, usize)> {
+        game.possible_instructions()
+            .into_iter()
+            .filter_map(|instruction| game.instruction_to_piles(instruction))
+            .collect()
+    }
+
     fn find_foundation_return_position() -> Option<(GameState, KlondikePile, KlondikePile)> {
         const MAX_SEED: u64 = 512;
         const MAX_STEPS: usize = 160;
@@ -1107,7 +1157,7 @@ mod tests {
             game.take_from_foundation = true;
 
             for _ in 0..MAX_STEPS {
-                let moves = game.possible_instructions();
+                let moves = legal_pile_moves(&game);
                 if let Some((from, to, _count)) = moves.iter().cloned().find(|(from, to, count)| {
                     *count == 1
                         && matches!(from, KlondikePile::Foundation(_))
@@ -1226,7 +1276,7 @@ mod tests {
         game.take_from_foundation = true;
         assert!(game.can_move_cards(&from, &to, 1));
         assert!(
-            game.possible_instructions()
+            legal_pile_moves(&game)
                 .iter()
                 .any(|(f, t, c)| *f == from && *t == to && *c == 1)
         );
@@ -1241,7 +1291,7 @@ mod tests {
         game.take_from_foundation = false;
         assert!(!game.can_move_cards(&from, &to, 1));
         assert!(
-            game.possible_instructions()
+            legal_pile_moves(&game)
                 .iter()
                 .all(|(f, t, _)| !matches!(f, KlondikePile::Foundation(_))
                     || !matches!(t, KlondikePile::Tableau(_)))

solitaire_core/src/lib.rs

@@ -8,9 +8,10 @@ pub mod klondike_adapter;
 // downstream crates (engine, wasm) can import from one place without a direct
 // `klondike` / `card_game` dep.
 //
-// `KlondikePileStack`, `SkipCards`, and `TableauStack` are intentionally NOT
+// `KlondikePileStack`, `SkipCards` and `TableauStack` are intentionally NOT
-// re-exported — they are only used internally in `klondike_adapter.rs` and do
+// re-exported — they are only used internally (in `klondike_adapter.rs` and
-// not appear in any public method signature.
+// when decoding instructions to piles in `instruction_to_piles`) and do not
+// appear in any public method signature.
 pub use card_game::{Card, Session};
 pub use klondike::{Foundation, Klondike, KlondikeInstruction, KlondikePile, Tableau};
 pub use klondike_adapter::DrawMode;

solitaire_core/src/proptest_tests.rs

@@ -60,27 +60,23 @@ fn draw_mode_strategy() -> impl Strategy<Value = DrawMode> {
 ///
 /// Each action is `(draw_flag, move_index)`:
 /// - `draw_flag = true`  → call `game.draw()`
-/// - `draw_flag = false` → pick the `move_index % len`th legal move from
+/// - `draw_flag = false` → pick the `move_index % len`th legal instruction
-///   `possible_instructions()` and execute it.
+///   from `possible_instructions()` and apply it via `apply_instruction()`.
 ///
-/// `possible_instructions()` may return `(Stock, Stock, 1)` for the
+/// `possible_instructions()` may return `RotateStock`, which
-/// RotateStock / draw action. `move_cards(Stock, Stock, 1)` is rejected by
+/// `apply_instruction()` dispatches to `game.draw()`; ordinary instructions
-/// the `from == to` guard, so those are dispatched to `game.draw()`.
+/// are equivalent to `move_cards(from, to, count)`.
 fn apply_random_actions(game: &mut GameState, actions: &[(bool, usize)]) {
     for &(do_draw, idx) in actions {
         if do_draw {
             let _ = game.draw();
         } else {
-            let instructions = game.possible_instructions();
+            let moves = game.possible_instructions();
-            if instructions.is_empty() {
+            if moves.is_empty() {
                 continue;
             }
-            let (from, to, count) = instructions[idx % instructions.len()];
+            let instruction = moves[idx % moves.len()];
-            if from == to {
+            let _ = game.apply_instruction(instruction);
-                let _ = game.draw();
-            } else {
-                let _ = game.move_cards(from, to, count);
-            }
         }
     }
 }
@@ -92,16 +88,12 @@ fn apply_one_move(game: &mut GameState, move_idx: usize) -> bool {
     if game.is_won() {
         return false;
     }
-    let instructions = game.possible_instructions();
+    let moves = game.possible_instructions();
-    if instructions.is_empty() {
+    if moves.is_empty() {
         return game.draw().is_ok();
     }
-    let (from, to, count) = instructions[move_idx % instructions.len()];
+    let instruction = moves[move_idx % moves.len()];
-    if from == to {
+    game.apply_instruction(instruction).is_ok()
-        game.draw().is_ok()
-    } else {
-        game.move_cards(from, to, count).is_ok()
-    }
 }
 
 // ---------------------------------------------------------------------------
@@ -258,17 +250,13 @@ proptest! {
         let mut game = GameState::new(seed, draw_mode);
         apply_random_actions(&mut game, &setup_actions);
 
-        for (from, to, count) in game.possible_instructions() {
+        for instruction in game.possible_instructions() {
             // Clone so each move is tried from the same starting state.
             let mut trial = game.clone();
-            let result = if from == to {
+            let result = trial.apply_instruction(instruction);
-                trial.draw()
-            } else {
-                trial.move_cards(from, to, count)
-            };
             prop_assert!(
                 result.is_ok(),
-                "possible_instructions() reported ({from:?} → {to:?} ×{count}) \
+                "possible_instructions() reported {instruction:?} \
                  as legal but the call returned Err: {result:?}",
             );
         }

solitaire_data/src/storage.rs

@@ -506,7 +506,7 @@ mod tests {
     /// will cause at least one pile to disagree.
     #[test]
     fn game_state_v4_mid_game_round_trip() {
-        use solitaire_core::KlondikePile;
+        use solitaire_core::KlondikeInstruction;
         use solitaire_core::game_state::GameState;
 
         let path = gs_path("v4_mid_game");
@@ -524,11 +524,13 @@ mod tests {
 
         // Execute the first available DstTableau or DstFoundation move so the
         // instruction history contains a type other than RotateStock.
-        let moves = gs.possible_instructions();
+        if let Some(instruction) = gs.possible_instructions().into_iter().find(|i| {
-        if let Some((from, to, count)) = moves.iter().copied().find(|(_, to, _)| {
+            matches!(
-            matches!(to, KlondikePile::Tableau(_) | KlondikePile::Foundation(_))
+                i,
+                KlondikeInstruction::DstTableau(_) | KlondikeInstruction::DstFoundation(_)
+            )
         }) {
-            let _ = gs.move_cards(from, to, count);
+            let _ = gs.apply_instruction(instruction);
         }
 
         // Undo once: verifies that `undo_count` is persisted and that the

solitaire_engine/src/card_plugin.rs

@@ -165,6 +165,29 @@ pub struct CardEntity {
     pub card: Card,
 }
 
+/// Render-side index mapping each live board card to its [`CardEntity`].
+///
+/// Maintained exclusively by [`rebuild_card_entity_index`] in `PostUpdate`,
+/// after the card-sync authority ([`sync_cards_on_change`]) and the resize
+/// re-snap have flushed their spawn/despawn `Commands`. Consumers treat it as
+/// read-only and must still call `Query::get(entity)` for components beyond the
+/// `Entity` id (the map yields only the id).
+///
+/// Keyed by `Card`, which is unique across all live board entities in
+/// single-deck Klondike. Transient entities (drag shadow, labels) carry no
+/// `CardEntity` component, so the rebuild — which scans `&CardEntity` — never
+/// records them.
+#[derive(Resource, Debug, Default)]
+pub struct CardEntityIndex(pub HashMap<Card, Entity>);
+
+impl CardEntityIndex {
+    /// Resolve a card to its live entity, if one is currently spawned.
+    #[inline]
+    pub fn get(&self, card: &Card) -> Option<Entity> {
+        self.0.get(card).copied()
+    }
+}
+
 /// Marker for the text child inside a card entity.
 #[derive(Component, Debug)]
 pub struct CardLabel;
@@ -431,6 +454,7 @@ impl Plugin for CardPlugin {
         // ensure it exists here. Under `DefaultPlugins` the call is a no-op.
         app.init_resource::<ButtonInput<MouseButton>>()
             .init_resource::<ResizeThrottle>()
+            .init_resource::<CardEntityIndex>()
             .add_message::<SettingsChangedEvent>()
             .add_message::<CardFlippedEvent>()
             .add_message::<CardFaceRevealedEvent>()
@@ -466,6 +490,36 @@ impl Plugin for CardPlugin {
             );
 
         app.add_systems(Update, resize_android_corner_labels);
+        app.add_systems(PostUpdate, rebuild_card_entity_index);
+    }
+}
+
+/// Rebuild the [`CardEntityIndex`] from the live `CardEntity` set.
+///
+/// Runs in `PostUpdate` so that all spawn/despawn `Commands` issued by
+/// [`sync_cards_on_change`] and [`snap_cards_on_window_resize`] in `Update`
+/// have been flushed at the `Update -> PostUpdate` apply-deferred boundary.
+/// Rebuilding from scratch (rather than incrementally patching at every
+/// spawn/despawn site — waste cards churn on every draw) keeps a single writer
+/// and makes a stale entry structurally impossible.
+///
+/// Gated to changed frames only: `Changed<CardEntity>` fires the frame a card
+/// is spawned, `RemovedComponents<CardEntity>` the frame one is despawned. The
+/// `card` field is write-once (never mutated in place), so card-reposition
+/// frames don't trip `Changed` and correctly skip the O(52) rebuild.
+fn rebuild_card_entity_index(
+    mut index: ResMut<CardEntityIndex>,
+    cards: Query<(Entity, &CardEntity)>,
+    changed: Query<(), Changed<CardEntity>>,
+    removed: RemovedComponents<CardEntity>,
+) {
+    if changed.is_empty() && removed.is_empty() {
+        return;
+    }
+    let map = &mut index.0;
+    map.clear();
+    for (entity, ce) in &cards {
+        map.insert(ce.card.clone(), entity);
     }
 }
 

solitaire_engine/src/input_plugin.rs

@@ -26,7 +26,7 @@ use bevy::prelude::*;
 use bevy::window::PrimaryWindow;
 #[cfg(not(target_os = "android"))]
 use bevy::window::{MonitorSelection, WindowMode};
-use solitaire_core::{Foundation, KlondikePile, Tableau};
+use solitaire_core::{Foundation, KlondikeInstruction, KlondikePile, Tableau};
 use solitaire_core::card::{Card, Suit};
 use solitaire_core::game_state::GameState;
 
@@ -350,7 +350,7 @@ pub fn find_heuristic_hint(
     }
     let idx = hint_cycle.0 % hints.len();
     hint_cycle.0 = hint_cycle.0.wrapping_add(1);
-    let (from, to, _count) = hints[idx];
+    let (from, to) = hints[idx];
     Some((from, to))
 }
 
@@ -1642,30 +1642,47 @@ fn handle_double_tap(
 /// Build the complete list of legal moves available in `game`, ordered so that
 /// upstream `klondike` priorities are preserved.
 ///
-/// Each entry is `(from, to, count)` — the same triple used by
+/// Each entry is `(from, to)` — the source and destination piles a hint
-/// [`MoveRequestEvent`]. The list may be empty when no move exists at all
+/// should highlight. Only single-card moves are surfaced; multi-card tableau
-/// (game is stuck).
+/// runs are filtered out by [`hint_piles`]. The list may be empty when no
+/// move exists at all (game is stuck).
 ///
 /// This is the backing data for the cycling hint system: the H key steps
 /// through `hints[HintCycleIndex % hints.len()]` on each press.
-pub fn all_hints(game: &GameState) -> Vec<(KlondikePile, KlondikePile, usize)> {
+pub fn all_hints(game: &GameState) -> Vec<(KlondikePile, KlondikePile)> {
     if game.has_test_pile_overrides() {
         return legacy_all_hints(game);
     }
 
     game.possible_instructions()
         .into_iter()
-        .filter(|(_, _, count)| *count == 1)
+        .filter_map(|instruction| hint_piles(game, instruction))
         .collect()
 }
 
+/// Project a [`KlondikeInstruction`] to the `(source, destination)` piles a
+/// hint should highlight, or `None` for a no-op or multi-card move.
+///
+/// Delegates the instruction→pile decode to the single owner of that mapping,
+/// [`GameState::instruction_to_piles`], and keeps only single-card moves
+/// (`count == 1`) — the hint highlight can represent exactly one source card.
+pub(crate) fn hint_piles(
+    game: &GameState,
+    instruction: KlondikeInstruction,
+) -> Option<(KlondikePile, KlondikePile)> {
+    match game.instruction_to_piles(instruction)? {
+        (from, to, 1) => Some((from, to)),
+        _ => None,
+    }
+}
+
 /// Legacy hint enumeration used only when test pile overrides are active.
 ///
 /// `possible_instructions()` reflects the internal upstream `Session` state.
 /// In test fixtures that inject synthetic piles via `set_test_*`, these
 /// synthetic piles can diverge from the session state; this fallback preserves
 /// deterministic test semantics in those fixtures.
-fn legacy_all_hints(game: &GameState) -> Vec<(KlondikePile, KlondikePile, usize)> {
+fn legacy_all_hints(game: &GameState) -> Vec<(KlondikePile, KlondikePile)> {
     let sources: Vec<KlondikePile> = {
         let mut s = vec![KlondikePile::Stock];
         for tableau in tableaus() {
@@ -1674,7 +1691,7 @@ fn legacy_all_hints(game: &GameState) -> Vec<(KlondikePile, KlondikePile, usize)
         s
     };
 
-    let mut hints: Vec<(KlondikePile, KlondikePile, usize)> = Vec::new();
+    let mut hints: Vec<(KlondikePile, KlondikePile)> = Vec::new();
 
     // Pass 1 — foundation moves (highest priority, shown first).
     for from in &sources {
@@ -1685,7 +1702,7 @@ fn legacy_all_hints(game: &GameState) -> Vec<(KlondikePile, KlondikePile, usize)
         for foundation in foundations() {
             let dest = KlondikePile::Foundation(foundation);
             if game.can_move_cards(from, &dest, 1) {
-                hints.push((*from, dest, 1));
+                hints.push((*from, dest));
                 break;
             }
         }
@@ -1700,14 +1717,14 @@ fn legacy_all_hints(game: &GameState) -> Vec<(KlondikePile, KlondikePile, usize)
         };
         let already_has_foundation_hint = hints
             .iter()
-            .any(|(f, t, _)| f == from && matches!(t, KlondikePile::Foundation(_)));
+            .any(|(f, t)| f == from && matches!(t, KlondikePile::Foundation(_)));
         if already_has_foundation_hint {
             continue;
         }
         for tableau in tableaus() {
             let dest = KlondikePile::Tableau(tableau);
             if game.can_move_cards(from, &dest, 1) {
-                hints.push((*from, dest, 1));
+                hints.push((*from, dest));
                 break;
             }
         }
@@ -1727,7 +1744,7 @@ fn legacy_all_hints(game: &GameState) -> Vec<(KlondikePile, KlondikePile, usize)
             for tableau in tableaus() {
                 let dest = KlondikePile::Tableau(tableau);
                 if game.can_move_cards(&from, &dest, 1) {
-                    hints.push((from, dest, 1));
+                    hints.push((from, dest));
                     break;
                 }
             }
@@ -1742,9 +1759,9 @@ fn legacy_all_hints(game: &GameState) -> Vec<(KlondikePile, KlondikePile, usize)
         let waste_can_recycle = stock_cards.is_empty() && !waste_cards.is_empty();
         if stock_non_empty || waste_can_recycle {
             // Stock→Waste is not a real pile-to-pile move, but we reuse the
-            // triple to signal "draw". The H handler only reads `from` to
+            // pair to signal "draw". The H handler only reads `from` to
             // locate the card to highlight; we point at the stock pile.
-            hints.push((KlondikePile::Stock, KlondikePile::Stock, 1));
+            hints.push((KlondikePile::Stock, KlondikePile::Stock));
         }
     }
 
@@ -1793,9 +1810,9 @@ const fn tableau_number(tableau: Tableau) -> u8 {
 
 /// Find one valid move in the current game state.
 ///
-/// Returns `(from, to, count)` for the first legal move found, or `None` if
+/// Returns `(from, to)` for the first legal move found, or `None` if
 /// no move is available. This is a convenience wrapper over [`all_hints`].
-pub fn find_hint(game: &GameState) -> Option<(KlondikePile, KlondikePile, usize)> {
+pub fn find_hint(game: &GameState) -> Option<(KlondikePile, KlondikePile)> {
     all_hints(game).into_iter().next()
 }
 
@@ -2166,10 +2183,9 @@ mod tests {
 
         let hint = find_hint(&game);
         assert!(hint.is_some(), "should find a hint");
-        let (from, to, count) = hint.unwrap();
+        let (from, to) = hint.unwrap();
         assert_eq!(from, KlondikePile::Tableau(Tableau::Tableau1));
         assert_eq!(to, KlondikePile::Foundation(Foundation::Foundation1));
-        assert_eq!(count, 1);
     }
 
     // -----------------------------------------------------------------------
@@ -2212,10 +2228,9 @@ mod tests {
 
         let hints = all_hints(&game);
         assert_eq!(hints.len(), 1, "exactly one hint: draw from stock");
-        let (from, to, count) = &hints[0];
+        let (from, to) = &hints[0];
         assert_eq!(*from, KlondikePile::Stock, "hint must come from Stock");
         assert_eq!(*to, KlondikePile::Stock, "hint must point to Waste");
-        assert_eq!(*count, 1);
     }
 
     // `all_hints` must be empty when both stock and waste are empty and no

solitaire_engine/src/pending_hint.rs

@@ -30,7 +30,7 @@ use solitaire_data::solver::try_solve_from_state;
 
 use crate::card_plugin::CardEntity;
 use crate::events::{HintVisualEvent, InfoToastEvent, StateChangedEvent};
-use crate::input_plugin::{emit_hint_visuals, find_heuristic_hint};
+use crate::input_plugin::{emit_hint_visuals, find_heuristic_hint, hint_piles};
 use crate::resources::{GameStateResource, HintCycleIndex};
 
 /// In-flight async work for the H-key hint.
@@ -93,7 +93,7 @@ struct HintTask {
 enum HintTaskOutput {
     /// Solver verdict was winnable; here is the first move on the solution
     /// path. Converted to highlighted `(from, to)` piles by the poll system
-    /// via [`GameState::instruction_to_move`].
+    /// via [`crate::input_plugin::hint_piles`].
     SolverMove(KlondikeInstruction),
     /// Solver was `Unwinnable` or `Inconclusive`. The poll system
     /// runs the legacy heuristic against the live `GameState` so the
@@ -153,10 +153,7 @@ pub fn poll_pending_hint_task(
     // Resolve the solver's first move to highlighted piles; fall back to the
     // live-state heuristic when there's no solver move or it maps to a no-op.
     let solver_pair = match output {
-        HintTaskOutput::SolverMove(instruction) => g
+        HintTaskOutput::SolverMove(instruction) => hint_piles(&g.0, instruction),
-            .0
-            .instruction_to_move(instruction)
-            .map(|(from, to, _count)| (from, to)),
         HintTaskOutput::NeedsHeuristic => None,
     };
     let (from, to) = match solver_pair.or_else(|| find_heuristic_hint(&g.0, &mut hint_cycle)) {

solitaire_engine/src/selection_plugin.rs

@@ -41,7 +41,7 @@ use solitaire_core::{Foundation, KlondikePile, Tableau};
 use solitaire_core::card::Card;
 use solitaire_core::game_state::GameState;
 
-use crate::card_plugin::CardEntity;
+use crate::card_plugin::CardEntityIndex;
 use crate::events::{InfoToastEvent, MoveRequestEvent, StateChangedEvent};
 use crate::game_plugin::GameMutation;
 use crate::input_plugin::{best_destination, best_tableau_destination_for_stack};
@@ -147,8 +147,12 @@ pub struct SelectionPlugin;
 
 impl Plugin for SelectionPlugin {
     fn build(&self, app: &mut App) {
+        // `CardEntityIndex` is owned and kept current by `CardPlugin`; this
+        // call is a no-op there. It is declared here so `update_selection_highlight`
+        // can read it via `Res<>` even in harnesses that omit `CardPlugin`.
         app.init_resource::<SelectionState>()
             .init_resource::<KeyboardDragState>()
+            .init_resource::<CardEntityIndex>()
             .add_systems(
                 Update,
                 (
@@ -657,7 +661,7 @@ fn update_selection_highlight(
     kbd_drag: Res<KeyboardDragState>,
     game: Res<GameStateResource>,
     layout: Option<Res<LayoutResource>>,
-    card_entities: Query<(Entity, &CardEntity)>,
+    card_index: Res<CardEntityIndex>,
     highlights: Query<Entity, With<SelectionHighlight>>,
 ) {
     // Always despawn any existing highlight first.
@@ -695,7 +699,7 @@ fn update_selection_highlight(
     {
         spawn_highlight_on_card(
             &mut commands,
-            &card_entities,
+            &card_index,
             &card,
             card_size,
             source_color,
@@ -712,7 +716,7 @@ fn update_selection_highlight(
         if let Some(card) = top_face_up_card(dest, &game.0) {
             spawn_highlight_on_card(
                 &mut commands,
-                &card_entities,
+                &card_index,
                 &card,
                 card_size,
                 dest_color,
@@ -741,13 +745,12 @@ fn pile_cards(game: &GameState, pile: &KlondikePile) -> Vec<(Card, bool)> {
 /// the matching `CardEntity::card`. No-op if no entity matches.
 fn spawn_highlight_on_card(
     commands: &mut Commands,
-    card_entities: &Query<(Entity, &CardEntity)>,
+    card_index: &CardEntityIndex,
     card: &Card,
     card_size: Vec2,
     color: Color,
 ) {
-    for (entity, card_entity) in card_entities {
+    if let Some(entity) = card_index.get(card) {
-        if card_entity.card == *card {
         commands.entity(entity).with_children(|b| {
             b.spawn((
                 SelectionHighlight,
@@ -760,8 +763,6 @@ fn spawn_highlight_on_card(
                 Visibility::default(),
             ));
         });
-            break;
-        }
     }
 }
 

solitaire_wasm/src/lib.rs

@@ -357,6 +357,7 @@ fn legal_moves_for_game(game: &GameState) -> Vec<DebugMove> {
     let mut moves: Vec<DebugMove> = game
         .possible_instructions()
         .into_iter()
+        .filter_map(|instruction| game.instruction_to_piles(instruction))
         .map(|(from, to, count)| DebugMove::Move {
             from: pile_name(from),
             to: pile_name(to),