From a6f66492cbc5a3470d74d53e2aaf8d231056b3cf Mon Sep 17 00:00:00 2001
From: Frankie-hz <105882754+Frankie-hz@users.noreply.github.com>
Date: Thu, 29 Oct 2026 21:31:25 -0400
Subject: [PATCH] Fix mob chase reading a cleared path after checking in-range

---
 .../systems/pathing/chase_target_on_top.lua   | 48 +++++++++++++++++++
 src/map/ai/controllers/mob_controller.cpp     |  4 +-
 2 files changed, 50 insertions(+), 2 deletions(-)
 create mode 100644 scripts/tests/systems/pathing/chase_target_on_top.lua

diff --git a/scripts/tests/systems/pathing/chase_target_on_top.lua b/scripts/tests/systems/pathing/chase_target_on_top.lua
new file mode 100644
index 00000000000..e52bd33ba63
--- /dev/null
+++ b/scripts/tests/systems/pathing/chase_target_on_top.lua
@@ -0,0 +1,48 @@
+-----------------------------------
+-- A chasing mob whose target lands within 1 yalm of it
+--
+-- The in-range directness probe clears the chase path when its navmesh query fails, which it always does under 1 yalm.
+-- Move() then read the destination of the cleared path, aborting builds with STL assertions (Linux ASAN, _MSVC_STL_HARDENING).
+-----------------------------------
+
+describe('Mob chase when the target lands on top of it', function()
+    ---@type CClientEntityPair
+    local player
+
+    ---@type CTestEntity
+    local mob
+
+    before_each(function()
+        player = xi.test.world:spawnPlayer({ zone = xi.zone.WEST_RONFAURE, level = 99 })
+        mob    = player.entities:moveTo('Wild_Rabbit')
+        mob:respawn()
+        mob:clearPath()
+        mob:setUnkillable(true)
+        mob:setBaseSpeed(40) -- the mob default, other tests leave this rabbit immobile
+    end)
+
+    it('settles on the target after the in-range probe clears its chase path', function()
+        local start = mob:getPos()
+        player:setPos(start.x - 10, start.y, start.z, 0)
+
+        mob:addEnmity(player, 100, 100)
+        mob:engage(player:getTargID())
+
+        for _ = 1, 5 do
+            xi.test.world:tickEntity(mob)
+            if mob:isFollowingPath() then
+                break
+            end
+        end
+
+        assert(mob:isFollowingPath(), 'mob should be chasing along a path')
+        assert(mob:checkDistance(player) > 3, 'mob should still be short of melee range')
+
+        local chasePos = mob:getPos()
+        player:setPos(chasePos.x + 0.5, chasePos.y, chasePos.z, 0)
+        xi.test.world:tickEntity(mob)
+
+        assert(mob:isEngaged(), 'mob should still be engaged on the player')
+        assert(not mob:isFollowingPath(), 'mob should settle on the player instead of walking a stale path')
+    end)
+end)
diff --git a/src/map/ai/controllers/mob_controller.cpp b/src/map/ai/controllers/mob_controller.cpp
index 303f5838d72..0f2c38b96eb 100644
--- a/src/map/ai/controllers/mob_controller.cpp
+++ b/src/map/ai/controllers/mob_controller.cpp
@@ -1251,7 +1251,6 @@ void CMobController::Move()
     }
 
     const float currentDistance = distance(PMob->loc.p, PTarget->loc.p);
-    const bool  isFollowingPath = PMob->PAI->PathFind->IsFollowingPath();
 
     // Teleport type 1: jump in if out of melee range but within 30y and off cooldown.
     if (PMob->getMobMod(xi::MobMod::TeleportType) == 1 &&
@@ -1341,7 +1340,8 @@ void CMobController::Move()
     bool needNewPath   = false;
     bool isStuckRepath = false;
     bool targetMoved   = false;
-    if (isFollowingPath)
+    // Read after the in-range probe, which clears the path when its query fails.
+    if (PMob->PAI->PathFind->IsFollowingPath())
     {
         needNewPath = !isWithinDistance(PMob->PAI->PathFind->GetDestination(), PTarget->loc.p, kChaseRepathDrift);
     }