solitaire_engine/src/card_plugin/mod.rs

@@ -570,8 +570,8 @@ impl Plugin for CardPlugin {
                     tick_flip_anim,
                     update_drag_shadow,
                     update_card_shadows_on_drag.after(sync_cards_on_change),
-                    tick_hint_highlight,
+                    tick_hint_highlight.after(GameMutation),
-                    handle_right_click,
+                    handle_right_click.after(GameMutation),
                     tick_right_click_highlights,
                     clear_right_click_highlights_on_state_change.after(GameMutation),
                     clear_right_click_highlights_on_pause,
@@ -580,7 +580,9 @@ impl Plugin for CardPlugin {
                         .after(GameMutation)
                         .run_if(resource_changed::<GameStateResource>),
                     collect_resize_events.after(LayoutSystem::UpdateOnResize),
-                    snap_cards_on_window_resize.after(collect_resize_events),
+                    snap_cards_on_window_resize
+                        .after(collect_resize_events)
+                        .after(GameMutation),
                 ),
             );
 

solitaire_engine/src/game_plugin/mod.rs

@@ -63,6 +63,18 @@ pub struct GameOverScreen;
 #[derive(SystemSet, Debug, Clone, PartialEq, Eq, Hash)]
 pub struct GameMutation;
 
+/// System set for every writer of [`crate::events::NewGameRequestEvent`].
+///
+/// Many UI entry points fire this trigger (buttons, keyboard, modals,
+/// mode pickers). Their relative append order within a frame is
+/// meaningless — consumers drain the whole queue — so members are
+/// registered `.in_set(NewGameRequestWriters).ambiguous_with(NewGameRequestWriters)`
+/// to declare writer-vs-writer order irrelevant instead of leaving it as an
+/// ambiguity (#143). Only ever combine with `.ambiguous_with` on the same
+/// set; do NOT hang ordering edges off this set.
+#[derive(SystemSet, Debug, Clone, PartialEq, Eq, Hash)]
+pub struct NewGameRequestWriters;
+
 /// Persistence path for the in-progress game state file. `None` disables I/O.
 #[derive(Resource, Debug, Clone)]
 pub struct GameStatePath(pub Option<PathBuf>);
@@ -208,7 +220,13 @@ impl Plugin for GamePlugin {
             .add_message::<AppLifecycle>()
             // add_message is idempotent; SettingsPlugin also registers this.
             .add_message::<crate::settings_plugin::SettingsChangedEvent>()
-            .add_systems(Update, poll_pending_new_game_seed.before(GameMutation))
+            .add_systems(
+                Update,
+                poll_pending_new_game_seed
+                    .before(GameMutation)
+                    .in_set(NewGameRequestWriters)
+                    .ambiguous_with(NewGameRequestWriters),
+            )
             .add_systems(
                 Update,
                 (handle_new_game, handle_draw, handle_move, handle_undo)
@@ -217,19 +235,40 @@ impl Plugin for GamePlugin {
             )
             .add_systems(Update, check_no_moves.after(GameMutation))
             .add_systems(Update, record_replay_on_win.after(GameMutation))
-            .add_systems(Update, handle_confirm_input.after(GameMutation))
+            .add_systems(
-            .add_systems(Update, handle_confirm_button_input.after(GameMutation))
+                Update,
-            .add_systems(Update, handle_game_over_input.after(GameMutation))
+                (
-            .add_systems(Update, handle_game_over_button_input.after(GameMutation))
+                    handle_confirm_input,
+                    handle_confirm_button_input,
+                    handle_game_over_input,
+                    handle_game_over_button_input,
+                )
+                    .after(GameMutation)
+                    .in_set(NewGameRequestWriters)
+                    .ambiguous_with(NewGameRequestWriters),
+            )
             // Restore prompt: spawn the modal once the splash is gone,
             // route Continue / New Game intents back into the existing
             // GameMutation flow.
             .add_systems(Update, spawn_restore_prompt_if_pending)
-            .add_systems(Update, handle_restore_prompt.before(GameMutation))
+            // All three pre-mutation game-state writers are chained: elapsed
-            .add_systems(Update, sync_settings_to_game.before(GameMutation))
+            // time ticks first, settings sync next, then the restore prompt —
+            // a deterministic spine instead of three unordered ResMut holders
+            // (ambiguity burn-down, #143).
+            .add_systems(
+                Update,
+                (
+                    tick_elapsed_time,
+                    sync_settings_to_game,
+                    handle_restore_prompt
+                        .in_set(NewGameRequestWriters)
+                        .ambiguous_with(NewGameRequestWriters),
+                )
+                    .chain()
+                    .before(GameMutation),
+            )
             .init_resource::<AutoSaveTimer>()
-            .add_systems(Update, tick_elapsed_time)
+            .add_systems(Update, auto_save_game_state.after(GameMutation))
-            .add_systems(Update, auto_save_game_state)
             .add_systems(Last, save_game_state_on_exit);
     }
 }

solitaire_engine/src/hud_plugin/mod.rs

@@ -36,7 +36,7 @@ use crate::events::{
     UndoRequestEvent, WinStreakMilestoneEvent,
 };
 use crate::font_plugin::FontResource;
-use crate::game_plugin::GameMutation;
+use crate::game_plugin::{GameMutation, NewGameRequestWriters};
 #[cfg(target_os = "android")]
 use crate::input_plugin::TouchDragSet;
 use crate::layout::HUD_BAND_HEIGHT;
@@ -478,10 +478,12 @@ impl Plugin for HudPlugin {
             .add_systems(Update, announce_auto_complete.after(GameMutation))
             .add_systems(
                 Update,
-                update_selection_hud.run_if(
+                update_selection_hud
-                    resource_exists_and_changed::<SelectionState>
+                    .after(GameMutation)
-                        .or(resource_exists_and_changed::<GameStateResource>),
+                    .run_if(
-                ),
+                        resource_exists_and_changed::<SelectionState>
+                            .or(resource_exists_and_changed::<GameStateResource>),
+                    ),
             )
             .add_systems(Update, update_hud_typography)
             .add_systems(
@@ -503,13 +505,17 @@ impl Plugin for HudPlugin {
             .add_systems(
                 Update,
                 (
-                    handle_new_game_button,
+                    handle_new_game_button
+                        .in_set(NewGameRequestWriters)
+                        .ambiguous_with(NewGameRequestWriters),
                     handle_undo_button,
                     handle_pause_button,
                     handle_help_button,
-                    handle_hint_button,
+                    handle_hint_button.after(GameMutation),
                     handle_modes_button,
-                    handle_mode_option_click,
+                    handle_mode_option_click
+                        .in_set(NewGameRequestWriters)
+                        .ambiguous_with(NewGameRequestWriters),
                     handle_modes_backdrop_click,
                     close_modes_popover_on_escape,
                     handle_menu_button,

solitaire_engine/src/schedule_checks.rs

@@ -38,7 +38,7 @@ mod tests {
     /// ordering edge — add `.before`/`.after` (order matters) or
     /// `.ambiguous_with` (provably order-independent) at the registration
     /// site. When triage lowers the real count, lower this constant too.
-    const AMBIGUITY_BASELINE: usize = 302;
+    const AMBIGUITY_BASELINE: usize = 198;
 
     fn cluster_app() -> App {
         let mut app = App::new();

solitaire_engine/src/table_plugin.rs

@@ -11,6 +11,7 @@ use solitaire_core::{FOUNDATIONS, TABLEAUS};
 use solitaire_core::Suit;
 
 use crate::events::{HintVisualEvent, StateChangedEvent};
+use crate::game_plugin::GameMutation;
 use crate::hud_plugin::HudVisibility;
 use crate::layout::{
     Layout, LayoutResource, LayoutSystem, TABLE_COLOUR, apply_dynamic_tableau_fan, compute_layout,
@@ -103,7 +104,7 @@ impl Plugin for TablePlugin {
                     apply_theme_on_settings_change,
                     apply_hint_pile_highlight,
                     tick_hint_pile_highlights,
-                    sync_pile_marker_visibility,
+                    sync_pile_marker_visibility.after(GameMutation),
                 ),
             );
     }