fix(physics): #32 L.2c wire edge-slide movement flag

docs/ISSUES.md

@@ -179,7 +179,7 @@ missing is the plugin-API surface.
 
 ## #32 — Retail edge-slide / cliff-slide / precipice-slide incomplete
 
-**Status:** OPEN
+**Status:** IN-PROGRESS
 **Severity:** HIGH
 **Filed:** 2026-04-29
 **Component:** physics / collision
@@ -188,7 +188,12 @@ missing is the plugin-API surface.
 step-down boundaries, retail often slides along the boundary. acdream still
 hard-blocks or accepts too much in several of these cases.
 
-**Root cause / status:** Tracked under Phase L.2c. Named retail anchors include
+**Root cause / status:** Tracked under Phase L.2c. Wall-adjacent
+`step_up_slide` now feels acceptable in live testing. L.2c plumbing now passes
+the retail-default `EdgeSlide` flag into local and remote movement and logs
+failed step-down edge cases behind `ACDREAM_DUMP_EDGE_SLIDE=1`. Remaining gap:
+preserve walkable polygon context for `precipice_slide` and finish
+`cliff_slide` / `NegPolyHit` dispatch. Named retail anchors include
 `CTransition::edge_slide`, `CTransition::cliff_slide`,
 `SPHEREPATH::precipice_slide`, and `SPHEREPATH::step_up_slide`.
 

memory/project_movement_collision_conformance.md

@@ -59,3 +59,8 @@ InputDispatcher / PlayerMovementController
   outdoor cell ownership from world position during the sphere sweep, so 24m
   outdoor seams update low cell ids and full-cell callers crossing landblock
   seams get the destination landblock prefix plus the correct outdoor low cell.
+- 2026-04-30: L.2c edge-slide plumbing. User live-tested wall-adjacent slide as
+  acceptable. Local player and remote dead-reckoning now pass retail-default
+  `ObjectInfoState.EdgeSlide`; `ACDREAM_DUMP_EDGE_SLIDE=1` logs failed
+  step-down edge cases so the next slice can distinguish missing walkable
+  polygon context from cliff-slide/NegPolyHit gaps.

src/AcDream.App/Input/PlayerMovementController.cs

@@ -428,12 +428,18 @@ public sealed class PlayerMovementController
             stepDownHeight: StepDownHeight,  // L.2.3a: from Setup.StepDownHeight
             isOnGround: _body.OnWalkable,
             body: _body,           // persist ContactPlane across frames for slope tracking
+            // L.2c 2026-04-30: retail PhysicsGlobals.DefaultState includes
+            // EdgeSlide, and PhysicsObj.get_object_info copies that bit into
+            // OBJECTINFO. Keep it explicit here so edge/cliff handling runs
+            // under the same flag profile as retail player movement.
+            //
             // Commit C 2026-04-29 — local player is always IsPlayer.
             // The PK/PKLite/Impenetrable bits come from PlayerDescription's
             // PlayerKillerStatus property; not yet parsed (non-PK pair → walks
             // through other non-PK players, which is retail's default for
             // ACE's character creation defaults too).
-            moverFlags: AcDream.Core.Physics.ObjectInfoState.IsPlayer);
+            moverFlags: AcDream.Core.Physics.ObjectInfoState.IsPlayer
+                      | AcDream.Core.Physics.ObjectInfoState.EdgeSlide);
 
         // Apply resolved position.
         _body.Position = resolveResult.Position;

src/AcDream.App/Rendering/GameWindow.cs

@@ -5856,7 +5856,11 @@ public sealed class GameWindow : IDisposable
                         // branch zeroes the +Z offset every step (same bug
                         // we hit on the local jump).
                         isOnGround: !rm.Airborne,
-                        body: rm.Body);          // persist ContactPlane across frames for slope tracking
+                        body: rm.Body,           // persist ContactPlane across frames for slope tracking
+                        // Retail default physics state includes EdgeSlide.
+                        // Remote dead-reckoning should exercise the same
+                        // edge/cliff branch as local movement.
+                        moverFlags: AcDream.Core.Physics.ObjectInfoState.EdgeSlide);
 
                     rm.Body.Position = resolveResult.Position;
                     if (resolveResult.CellId != 0)

src/AcDream.Core/Physics/TransitionTypes.cs

@@ -345,6 +345,9 @@ public sealed class Transition
     public SpherePath SpherePath = new();
     public CollisionInfo CollisionInfo = new();
 
+    private static bool DumpEdgeSlideEnabled =>
+        Environment.GetEnvironmentVariable("ACDREAM_DUMP_EDGE_SLIDE") == "1";
+
     // -----------------------------------------------------------------------
     // Public entry point
     // -----------------------------------------------------------------------
@@ -665,18 +668,19 @@ public sealed class Transition
                     }
                 }
 
-                // L.2.3e (2026-04-29): step-down failed — the move would put
+                // L.2c (2026-04-30): step-down failed — the move would put
                 // the player off an edge with no walkable surface within reach.
-                // Retail's EdgeSlide (ACE Transition.cs:268-320) maps this to
-                // SetEdgeSlide(true, true, OK) which restores CheckPos to the
-                // saved (post-step) position — but our outer ValidateTransition
-                // accepts CheckPos as the new CurPos, defeating the intent.
+                // Retail's EdgeSlide path then needs either:
+                //   - a steep contact plane for CliffSlide, or
+                //   - SpherePath.Walkable polygon context for PrecipiceSlide.
                 //
-                // Returning Collided here makes ValidateTransition revert to
-                // CurPos (pre-step) — the always-on retail "stop at edge"
-                // behavior. Confirmed against ACE Transition.cs:317 where
-                // EdgeSlide returns Collided when no walkable surface is
-                // found and the EdgeSlide flag is unset (player default).
+                // acdream does not yet preserve the full walkable polygon
+                // context from terrain/BSP step-down, so this is still the
+                // conservative stop-at-edge fallback. The diagnostic below is
+                // intentionally narrow: it tells the next L.2c slice whether
+                // we are missing precipice context, a steep contact plane, or
+                // merely the EdgeSlide flag.
+                DumpEdgeSlideStepDownFailed(stepDownHeight, zVal);
                 sp.RestoreCheckPos();
                 return TransitionState.Collided;
             }
@@ -689,6 +693,22 @@ public sealed class Transition
         return TransitionState.Slid;
     }
 
+    private void DumpEdgeSlideStepDownFailed(float stepDownHeight, float zVal)
+    {
+        if (!DumpEdgeSlideEnabled) return;
+
+        var sp = SpherePath;
+        var ci = CollisionInfo;
+        var oi = ObjectInfo;
+
+        Console.WriteLine(
+            System.FormattableString.Invariant(
+                $"edge-slide: stepdown-failed cur={Fmt(sp.CurPos)} check={Fmt(sp.CheckPos)} cell=0x{sp.CheckCellId:X8} edgeFlag={oi.EdgeSlide} contactFlag={oi.Contact} onWalkable={oi.OnWalkable} contactPlane={ci.ContactPlaneValid} lastPlane={ci.LastKnownContactPlaneValid} walkableValid={sp.WalkableValid} stepDown={stepDownHeight:F3} zVal={zVal:F3}"));
+    }
+
+    private static string Fmt(Vector3 value) =>
+        System.FormattableString.Invariant($"({value.X:F3},{value.Y:F3},{value.Z:F3})");
+
     // -----------------------------------------------------------------------
     // Environment collision — outdoor terrain
     // -----------------------------------------------------------------------

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

@@ -210,6 +210,27 @@ public class PhysicsEngineTests
         Assert.Equal(0x0009u, result.CellId);
     }
 
+    [Fact]
+    public void ResolveWithTransition_EdgeSlideFlag_AllowsNormalFlatMovement()
+    {
+        var engine = MakeFlatEngine(terrainZ: 50f);
+
+        var result = engine.ResolveWithTransition(
+            currentPos: new Vector3(96f, 96f, 50f),
+            targetPos:  new Vector3(98f, 96f, 50f),
+            cellId: 0x0025u,
+            sphereRadius: 0.5f,
+            sphereHeight: 1.2f,
+            stepUpHeight: 0.4f,
+            stepDownHeight: 0.4f,
+            isOnGround: true,
+            moverFlags: ObjectInfoState.EdgeSlide);
+
+        Assert.True(result.IsOnGround);
+        Assert.InRange(result.Position.X, 97.9f, 98.1f);
+        Assert.Equal(0x0025u, result.CellId);
+    }
+
     [Fact]
     public void ResolveWithTransition_LandblockBoundary_UpdatesFullOutdoorCellId()
     {