diff --git a/server/.clippy.toml b/server/.clippy.toml
new file mode 100644
index 000000000..88f1e5b57
--- /dev/null
+++ b/server/.clippy.toml
@@ -0,0 +1,9 @@
+# Clippy configuration for settled-reach-server
+# Enforces determinism-safe collection types in simulation code (D-030).
+
+# Ban std::collections::HashMap — non-deterministic iteration order breaks replay.
+# Use BTreeMap (ordered by key) or IndexMap (insertion-ordered) instead.
+disallowed-types = [
+    { path = "std::collections::HashMap", reason = "HashMap iteration order is non-deterministic. Use BTreeMap or IndexMap for deterministic simulation." },
+    { path = "std::collections::HashSet", reason = "HashSet iteration order is non-deterministic. Use BTreeSet or IndexSet." },
+]
diff --git a/server/src/perception/query.rs b/server/src/perception/query.rs
index 9789f884d..af6057345 100644
--- a/server/src/perception/query.rs
+++ b/server/src/perception/query.rs
@@ -4,6 +4,11 @@
 //! (natural vision, thermal, EM, etc.) implements PerceptionQuery to
 //! provide mode-specific FOV and visibility sector computation.
 //! v0.1 implements only NaturalVision.
+//!
+//! Note: HashMap is used for `sector_lookup` — a per-frame scratch buffer
+//! looked up only by key. Iteration order is irrelevant here. Not subject to
+//! the simulation determinism constraint (see server/.clippy.toml).
+#![allow(clippy::disallowed_types)]
 
 use std::collections::{BTreeSet, HashMap};
 
diff --git a/server/src/simulation/movement.rs b/server/src/simulation/movement.rs
index 5fd5e7aec..027ffa166 100644
--- a/server/src/simulation/movement.rs
+++ b/server/src/simulation/movement.rs
@@ -6,7 +6,7 @@
 
 use bevy_ecs::prelude::*;
 use serde::{Deserialize, Serialize};
-use std::collections::HashMap;
+use std::collections::BTreeMap;
 
 /// Chunk size in tiles (32x32 per chunk)
 pub const CHUNK_SIZE: i32 = 32;
@@ -22,7 +22,10 @@ pub struct PlayerCharacter;
 ///
 /// Examples: a Standing character can walk past a Seated NPC at a console,
 /// a Fixture (terminal) shares a tile with someone Seated at it.
-#[derive(Component, Debug, Clone, Copy, PartialEq, Eq, Hash, Default, Serialize, Deserialize)]
+#[derive(
+    Component, Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord, Default, Serialize,
+    Deserialize,
+)]
 pub enum TilePresence {
     /// Upright position — walking, standing, sprinting. Default for all entities.
     #[default]
@@ -39,7 +42,7 @@ pub enum TilePresence {
 /// Tile position component for grid-based movement.
 /// Discrete integer coordinates used in simulation; converted to f32
 /// at the bridge boundary for VisibleEntity wire format.
-#[derive(Component, Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
+#[derive(Component, Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord, Serialize, Deserialize)]
 pub struct TilePosition {
     pub x: i32,
     pub y: i32,
@@ -116,7 +119,7 @@ impl TilePosition {
 }
 
 /// Chunk coordinate for chunk-based map storage (D-012).
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub struct ChunkCoord {
     pub cx: i32,
     pub cy: i32,
@@ -161,14 +164,14 @@ impl ChunkData {
 /// Unloaded chunks are treated as unwalkable.
 #[derive(Resource, Debug, Clone)]
 pub struct WalkabilityMap {
-    chunks: HashMap<ChunkCoord, ChunkData>,
+    chunks: BTreeMap<ChunkCoord, ChunkData>,
 }
 
 impl WalkabilityMap {
     /// Create a walkability map covering a rectangular area with all tiles walkable.
     /// Generates chunks to cover the specified dimensions on z-level 0..z_levels.
     pub fn new(width: i32, height: i32, z_levels: i32) -> Self {
-        let mut chunks = HashMap::new();
+        let mut chunks = BTreeMap::new();
         let cx_max = (width + CHUNK_SIZE - 1) / CHUNK_SIZE;
         let cy_max = (height + CHUNK_SIZE - 1) / CHUNK_SIZE;
         for z in 0..z_levels {
@@ -183,7 +186,7 @@ impl WalkabilityMap {
 
     /// Create a walkability map covering a rectangular area with all tiles blocked.
     pub fn new_blocked(width: i32, height: i32, z_levels: i32) -> Self {
-        let mut chunks = HashMap::new();
+        let mut chunks = BTreeMap::new();
         let cx_max = (width + CHUNK_SIZE - 1) / CHUNK_SIZE;
         let cy_max = (height + CHUNK_SIZE - 1) / CHUNK_SIZE;
         for z in 0..z_levels {
@@ -279,7 +282,7 @@ pub fn validate_movement(
 
     // Collect layer slots occupied by stationary entities (no MoveIntent).
     // Key: (position, layer) — two entities can share a tile if different layers.
-    let mut occupied: HashMap<(TilePosition, TilePresence), Entity> = HashMap::new();
+    let mut occupied: BTreeMap<(TilePosition, TilePresence), Entity> = BTreeMap::new();
     for (entity, pos, presence) in stationary.iter() {
         let layer = presence.copied().unwrap_or_default();
         occupied.insert((*pos, layer), entity);