diff --git a/server/src/systems/__tests__/statModifierSystem.test.ts b/server/src/systems/__tests__/statModifierSystem.test.ts
index 8c2953b..fd9051c 100644
--- a/server/src/systems/__tests__/statModifierSystem.test.ts
+++ b/server/src/systems/__tests__/statModifierSystem.test.ts
@@ -21,7 +21,7 @@ function setupEntity(
   world.addComponent<Stats>(e, 'stats', base);
   world.addComponent<StatModifiers>(e, 'statModifiers', { modifiers: [...modifiers] });
   if (needs) {
-    world.addComponent<Needs>(e, 'needs', { hunger: 80, energy: 80, productivity: 80, ...needs });
+    world.addComponent<Needs>(e, 'needs', { hunger: 80, energy: 80, thirst: 80, productivity: 80, ...needs });
   }
   return e;
 }
@@ -97,6 +97,17 @@ describe('statModifierSystem', () => {
       expect(needsMods).toHaveLength(0);
     });
 
+    it('applies perception -2 and constitution -1 when thirst < threshold', () => {
+      const world = new World();
+      const e = setupEntity(world, {}, { thirst: 20, hunger: 80, energy: 80 });
+      statModifierSystem(world, rc);
+      const mods = world.getComponent<StatModifiers>(e, 'statModifiers')!;
+      const perMod = mods.modifiers.find(m => m.stat === 'perception' && m.remaining === -1);
+      const conMod = mods.modifiers.find(m => m.stat === 'constitution' && m.remaining === -1);
+      expect(perMod?.value).toBe(-2);
+      expect(conMod?.value).toBe(-1);
+    });
+
     it('does not stack needs-based modifiers across ticks', () => {
       const world = new World();
       const e = setupEntity(world, {}, { hunger: 20, energy: 80 });
diff --git a/server/src/systems/statModifierSystem.ts b/server/src/systems/statModifierSystem.ts
index b2f9a16..b9583f3 100644
--- a/server/src/systems/statModifierSystem.ts
+++ b/server/src/systems/statModifierSystem.ts
@@ -15,6 +15,10 @@ function applyNeedsModifiers(needs: Needs, modifiers: StatModifier[], rc: Runtim
     filtered.push({ stat: 'dexterity', value: -2, remaining: -1 });
     filtered.push({ stat: 'temperament', value: -2, remaining: -1 });
   }
+  if (needs.thirst < rc.get('THIRST_THRESHOLD')) {
+    filtered.push({ stat: 'perception', value: -2, remaining: -1 });
+    filtered.push({ stat: 'constitution', value: -1, remaining: -1 });
+  }
 
   return filtered;
 }