fix(physics): preserve refreshed cell retry state

src/AcDream.Core/Physics/PhysicsEngine.cs

@@ -70,6 +70,7 @@ public sealed class PhysicsEngine
     /// response coupling.
     /// </summary>
     internal Func<
+        Transition,
         TransitionCellCollisionPhase,
         uint,
         TransitionState,

src/AcDream.Core/Physics/TransitionTypes.cs

@@ -1728,6 +1728,11 @@ public sealed class Transition
     /// The former flat per-landblock object query is gone.
     /// </para>
     /// </summary>
+    internal TransitionState TransitionalInsertForTest(
+        int numAttempts,
+        PhysicsEngine engine)
+        => TransitionalInsert(numAttempts, engine);
+
     private TransitionState TransitionalInsert(int numAttempts, PhysicsEngine engine)
     {
         if (SpherePath.CheckCellId == 0) return TransitionState.OK;
@@ -2133,7 +2138,7 @@ public sealed class Transition
         TransitionState state = TransitionState.OK;
         for (int attempt = 0; attempt < numAttempts; attempt++)
         {
-            state = FindPrimaryCellCollisions(engine, cellId, attempt);
+            state = FindPrimaryCellCollisions(engine, attempt);
             if (state is TransitionState.OK or TransitionState.Collided)
                 return state;
 
@@ -2154,41 +2159,42 @@ public sealed class Transition
     /// </summary>
     private TransitionState FindPrimaryCellCollisions(
         PhysicsEngine engine,
-        uint cellId,
         int innerAttempt)
     {
+        TransitionState actualEnvironment = FindEnvCollisions(engine);
+        uint currentCellId = SpherePath.CheckCellId;
         TransitionState environment = ObservePrimaryCellPhase(
             engine,
             TransitionCellCollisionPhase.Environment,
-            cellId,
-            FindEnvCollisions(engine));
+            currentCellId,
+            actualEnvironment);
         if (environment != TransitionState.OK)
             return environment;
 
         TransitionState building = ObservePrimaryCellPhase(
             engine,
             TransitionCellCollisionPhase.Building,
-            cellId,
-            FindBuildingCollisions(engine, cellId));
+            currentCellId,
+            FindBuildingCollisions(engine, currentCellId));
         if (building != TransitionState.OK)
             return building;
 
         TransitionState objects = ObservePrimaryCellPhase(
             engine,
             TransitionCellCollisionPhase.Objects,
-            cellId,
-            FindObjCollisionsInCell(engine, cellId));
+            currentCellId,
+            FindObjCollisionsInCell(engine, currentCellId));
         DumpPhase2(innerAttempt, environment, objects);
         return objects;
     }
 
-    private static TransitionState ObservePrimaryCellPhase(
+    private TransitionState ObservePrimaryCellPhase(
         PhysicsEngine engine,
         TransitionCellCollisionPhase phase,
         uint cellId,
         TransitionState actual)
         => engine.TransitionCellCollisionTestHook is { } hook
-            ? hook(phase, cellId, actual)
+            ? hook(this, phase, cellId, actual)
             : actual;
 
     private TransitionState EdgeSlideAfterStepDownFailed(

tests/AcDream.Core.Tests/Physics/TransitionInsertIntoCellRetryTests.cs

@@ -31,7 +31,7 @@ public sealed class TransitionInsertIntoCellRetryTests
         int buildingCalls = 0;
         int objectCalls = 0;
 
-        engine.TransitionCellCollisionTestHook = (phase, cellId, actual) =>
+        engine.TransitionCellCollisionTestHook = (_, phase, cellId, actual) =>
         {
             Assert.Equal(Cell, cellId);
             Assert.Equal(TransitionState.OK, actual);
@@ -109,6 +109,148 @@ public sealed class TransitionInsertIntoCellRetryTests
             + "outer N=3 budget while remaining inside retail's N×N budget.");
     }
 
+    [Fact]
+    public void NestedRetry_AlwaysAdjusted_ExhaustsExactNByNBudget()
+    {
+        PhysicsEngine engine = BuildEngine(preparedFlat: false);
+        int calls = 0;
+        engine.TransitionCellCollisionTestHook =
+            (_, phase, cellId, actual) =>
+            {
+                Assert.Equal(TransitionCellCollisionPhase.Environment, phase);
+                Assert.Equal(Cell, cellId);
+                Assert.Equal(TransitionState.OK, actual);
+                calls++;
+                return TransitionState.Adjusted;
+            };
+
+        Vector3 current = new(10f, 10f, 5f);
+        Vector3 target = current + new Vector3(0.05f, 0f, 0f);
+        Transition transition = BSPStepUpFixtures.MakeAirborneTransition(
+            current,
+            target,
+            Cell);
+        transition.SpherePath.SetCheckPos(target, Cell);
+        TransitionState result = transition.TransitionalInsertForTest(3, engine);
+
+        Assert.Equal(TransitionState.Adjusted, result);
+        Assert.Equal(target, transition.SpherePath.CheckPos);
+        Assert.Equal(9, calls);
+    }
+
+    [Fact]
+    public void NestedRetry_SlidClearsInnerContact_ThenOuterNegPoly()
+    {
+        PhysicsEngine engine = BuildEngine(preparedFlat: false);
+        int environmentCalls = 0;
+        var contactPlane = new Plane(Vector3.UnitZ, -5f);
+
+        engine.TransitionCellCollisionTestHook =
+            (transition, phase, _, actual) =>
+            {
+                if (phase != TransitionCellCollisionPhase.Environment)
+                    return actual;
+
+                environmentCalls++;
+                if (environmentCalls <= 3)
+                {
+                    if (environmentCalls > 1)
+                    {
+                        Assert.False(transition.CollisionInfo.ContactPlaneValid);
+                        Assert.False(transition.CollisionInfo.ContactPlaneIsWater);
+                        Assert.True(transition.SpherePath.NegPolyHit);
+                    }
+
+                    transition.CollisionInfo.SetContactPlane(
+                        contactPlane,
+                        Cell,
+                        isWater: true);
+                    transition.SpherePath.NegPolyHit = true;
+                    return TransitionState.Slid;
+                }
+
+                // Three Slid responses exhaust the first inner N=3 budget.
+                // Its final Slid clear removes contact/water; the outer
+                // transitional_insert boundary additionally removes neg-poly.
+                Assert.False(transition.CollisionInfo.ContactPlaneValid);
+                Assert.False(transition.CollisionInfo.ContactPlaneIsWater);
+                Assert.False(transition.SpherePath.NegPolyHit);
+                return actual;
+            };
+
+        Vector3 current = new(10f, 10f, 5f);
+        ResolveResult result = ResolveAirborne(
+            engine,
+            current,
+            current + new Vector3(0.05f, 0f, 0f),
+            Cell);
+
+        Assert.True(result.Ok);
+        Assert.Equal(4, environmentCalls);
+    }
+
+    [Fact]
+    public void NoDataCache_CrossLandblockRepick_UsesRefreshedPrimaryCell()
+    {
+        PhysicsEngine engine = BuildCrossLandblockEngine();
+        var cells = new List<uint>();
+        var phases = new List<TransitionCellCollisionPhase>();
+        engine.TransitionCellCollisionTestHook =
+            (_, phase, cellId, actual) =>
+            {
+                phases.Add(phase);
+                cells.Add(cellId);
+                return actual;
+            };
+
+        Vector3 current = new(191.99f, 10f, 5f);
+        Vector3 target = new(192.01f, 10f, 5f);
+        ResolveResult result = ResolveAirborne(
+            engine,
+            current,
+            target,
+            0xA9B40039u);
+
+        Assert.True(result.Ok);
+        Assert.Equal(target, result.Position);
+        Assert.Equal(0xAAB40001u, result.CellId);
+        Assert.Equal(
+            new[]
+            {
+                TransitionCellCollisionPhase.Environment,
+                TransitionCellCollisionPhase.Building,
+                TransitionCellCollisionPhase.Objects,
+            },
+            phases);
+        Assert.All(cells, cellId => Assert.Equal(0xAAB40001u, cellId));
+    }
+
+    private static ResolveResult ResolveAirborne(
+        PhysicsEngine engine,
+        Vector3 current,
+        Vector3 target,
+        uint cellId)
+    {
+        var body = new PhysicsBody
+        {
+            Position = current,
+            Orientation = Quaternion.Identity,
+            TransientState = TransientStateFlags.Active,
+        };
+        return engine.ResolveWithTransition(
+            current,
+            target,
+            cellId,
+            sphereRadius: 0.48f,
+            sphereHeight: 1.835f,
+            stepUpHeight: 0.6f,
+            stepDownHeight: 1.5f,
+            isOnGround: false,
+            body,
+            moverFlags: ObjectInfoState.IsPlayer | ObjectInfoState.EdgeSlide,
+            movingEntityId: 0x000F4243u);
+    }
+
     private static PhysicsEngine BuildEngine(bool preparedFlat)
     {
         var (root, resolved) = BSPStepUpFixtures.FlatRoof();
@@ -166,4 +308,27 @@ public sealed class TransitionInsertIntoCellRetryTests
             0f);
         return engine;
     }
+
+    private static PhysicsEngine BuildCrossLandblockEngine()
+    {
+        var engine = new PhysicsEngine { DataCache = null };
+        var heights = new byte[81];
+        var heightTable = new float[256];
+        Array.Fill(heightTable, -1000f);
+        engine.AddLandblock(
+            0xA9B4FFFFu,
+            new TerrainSurface(heights, heightTable),
+            Array.Empty<CellSurface>(),
+            Array.Empty<PortalPlane>(),
+            0f,
+            0f);
+        engine.AddLandblock(
+            0xAAB4FFFFu,
+            new TerrainSurface(heights, heightTable),
+            Array.Empty<CellSurface>(),
+            Array.Empty<PortalPlane>(),
+            192f,
+            0f);
+        return engine;
+    }
 }