fix

src/entities/tasks/components.rs

@@ -7,12 +7,12 @@
 //! - All task data is owned — no references to world state — for cache locality.
 //!
 //! # Performance
-//! - SmallVec<[Task; 4]> for queue — avoids heap alloc for typical short queues.
+//! - VecDeque for queue — O(1) push/pop at both ends.
 //! - Task enum is #[repr(u8)] for compact storage and fast matching.
 //! - No dynamic dispatch — match on Task variant directly in executor.
 
 use bevy::prelude::*;
-use smallvec::SmallVec;
+use std::collections::VecDeque;
 
 /// A single task an entity can execute.
 ///
@@ -88,10 +88,10 @@ impl Task {
 /// Tasks are pushed to the back; executor pops from front when complete.
 /// Higher-priority tasks can be inserted at front via `push_front`.
 ///
-/// Uses SmallVec to avoid heap allocation for typical queue lengths (<4 tasks).
+/// Uses VecDeque for O(1) push/pop at both ends.
 #[derive(Component, Debug, Default)]
 pub struct TaskQueue {
-    pub tasks: SmallVec<[Task; 4]>,
+    pub tasks: VecDeque<Task>,
 }
 
 impl TaskQueue {
@@ -102,31 +102,27 @@ impl TaskQueue {
 
     #[inline]
     pub fn current(&self) -> Option<&Task> {
-        self.tasks.first()
+        self.tasks.front()
     }
 
     #[inline]
     pub fn current_mut(&mut self) -> Option<&mut Task> {
-        self.tasks.first_mut()
+        self.tasks.front_mut()
     }
 
     #[inline]
     pub fn push(&mut self, task: Task) {
-        self.tasks.push(task);
+        self.tasks.push_back(task);
     }
 
     #[inline]
     pub fn push_front(&mut self, task: Task) {
-        self.tasks.insert(0, task);
+        self.tasks.push_front(task);
     }
 
     #[inline]
     pub fn pop(&mut self) -> Option<Task> {
-        if self.tasks.is_empty() {
-            None
-        } else {
-            Some(self.tasks.remove(0))
-        }
+        self.tasks.pop_front()
     }
 
     #[inline]

src/entities/tasks/executor.rs

@@ -33,8 +33,11 @@ pub fn task_executor_system(
     mut completed_writer: MessageWriter<TaskCompleted>,
     mut failed_writer: MessageWriter<TaskFailed>,
 ) {
-    let Ok(mut rng) = rng_q.single_mut() else {
-        return;
+    // Get mutable access to the single GlobalRng entity
+    // This must be done once per frame, not per entity
+    let mut rng = match rng_q.single_mut() {
+        Ok(r) => r,
+        Err(_) => return, // No GlobalRng entity exists yet
     };
 
     for (entity, mut queue, mut state, mut ambulatory, transform) in query.iter_mut() {

src/entities/tasks/idle.rs

@@ -31,33 +31,42 @@ pub(super) fn execute_idle(
 
     let entity_pos = (transform.translation / ITILE_SIZE as f32).as_ivec3();
 
+    // Track if target actually changed this tick
+    let mut target_changed = false;
+
     // If reached target or target is no longer standable, pick new target
     if entity_pos == *target || !tilemap.is_standable(*target) {
         if let Some(new_target) = pick_wander_target(origin, *wander_radius, tilemap, rng) {
             *target = new_target;
+            target_changed = true;
         }
     }
 
-    // Set ambulatory target - pathfinding system will compute path
-    ambulatory.target = Some(Vec3::new(
-        target.x as f32,
-        target.y as f32,
-        transform.translation.z,
-    ));
-    ambulatory.current_path = None;
-    ambulatory.path_index = 0;
+    // Only reset path if target changed or no path exists
+    // This avoids forcing pathfinding to recompute every frame
+    if target_changed || ambulatory.current_path.is_none() {
+        ambulatory.target = Some(Vec3::new(
+            target.x as f32,
+            target.y as f32,
+            transform.translation.z,
+        ));
+        ambulatory.current_path = None;
+        ambulatory.path_index = 0;
+    }
+    // Otherwise: keep existing path, let movement system continue along it
 }
 
 /// Pick a random standable tile within wander radius of origin.
+/// Uses reservoir sampling to avoid heap allocation.
 fn pick_wander_target(
     origin: &IVec3,
     radius: i32,
     tilemap: &TileMap,
     rng: &mut WyRand,
 ) -> Option<IVec3> {
-    let mut candidates = smallvec::SmallVec::<[IVec3; 16]>::new();
+    let mut chosen = None;
+    let mut count = 0u32;
 
-    // Collect valid tiles within radius
     for dx in -radius..=radius {
         for dy in -radius..=radius {
             let candidate = IVec3::new(
@@ -66,15 +75,13 @@ fn pick_wander_target(
                 origin.z,
             );
             if tilemap.is_standable(candidate) {
-                candidates.push(candidate);
+                count += 1;
+                // Reservoir sampling: 1/count chance to replace chosen
+                if rng.random_range(0..count) == 0 {
+                    chosen = Some(candidate);
+                }
             }
         }
     }
-
-    if candidates.is_empty() {
-        return None;
-    }
-
-    let idx = rng.random_range(0..candidates.len());
-    Some(candidates[idx])
+    chosen
 }