Body step 2.2: fix the 2.1 headset instabilities

Spike now runs real input (90 Hz sample-and-hold tracking + jitter under 144 Hz
physics), which reproduced the playtest. Root causes fixed:
- PoseFilter/RagdollDriver: timestamped extrapolation of tracking, one tick
  pipeline shared by PlayerRig and the spike
- low-pass all feed-forwards (ground control amplified jitter by body mass)
- arm muscles back to local targets (physical-frame aim fed chest rotation back)
- structural hand strength only when braced or holding
- no free-path view chasing while grounded (8 m crouch slide); stick hold-back
- explicit inertia for the Legs body (shape-less tuck tumbled the pelvis)
- world grab: Box3D shape queries return a null collider, use collider_id
- new crouch-hold phases; world-grab detection asserted

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

AGENTS.md

@@ -306,6 +306,12 @@ device only; the editor has an XR simulator for dev. Trackers/action map: see `x
    smooth turn, **physics 144 Hz with physics interpolation** (`Main.PhysicsRate`; XROrigin3D, TrueBody, PlayerRig
    are interpolation-OFF because they move per frame — anything new moved in `_Process` must be excluded too).
    Rule learned: play-space corrections must never feed ground control's feed-forward (runaway feedback).
+   **Step 2.2 (2.1 playtest was unstable — see research doc "Step 2.2"): RagdollSpike now runs REAL input
+   (90 Hz sample-and-hold tracking + jitter under 144 Hz physics); a body test on ideal input proves nothing.**
+   Tick pipeline = `RagdollDriver` (shared by PlayerRig and the spike; `PoseFilter` extrapolates tracking).
+   Rules: low-pass every feed-forward; muscles stay local to the TARGET pose (never the physical parent — rotation
+   feedback); no free-path view chasing while grounded; bodies whose shapes can all be disabled need explicit
+   inertia; Box3D shape queries return a null `collider` — use `collider_id`.
    Owner scope: thumbstick locomotion only, no jump, avatar scaling and NPCs later.
 10. **Body physics Stage 2 — PHYSICAL ARMS, implemented 2026-10-02, awaiting owner playtest.**
    `PhysicsArms.cs`: per side an upper-arm + forearm RigidBody3D (2.0 / 1.2 kg, layer 5) that

HANDOFF.md

@@ -103,6 +103,10 @@ TERMINOLOGY (owner-corrected — use precisely):
   static or arms lifting) = the only state that drags the view vertically, ground feed-forward that ignores play-space
   corrections (a runaway at 7 m/s otherwise), `ProceduralLegs` visuals, static-world grabs (climbing), menu strength
   slider / spectator / snap-smooth toggles, 144 Hz + physics interpolation (XR origin, TrueBody, PlayerRig excluded).
+- **RagdollDriver.cs (step 2.2)** — `PoseFilter` (timestamps each new tracking sample, extrapolates between them in
+  play-space-local space; 90 Hz tracking under 144 Hz physics otherwise feeds jerks into every feed-forward) and
+  `RagdollDriver` (filter → OriginCorrection → True Body → build → Step), used by BOTH PlayerRig and RagdollSpike.
+  The 2.1 instabilities, their root causes and fixes: `research/ragdoll-player-step2.md` "Step 2.2".
 - **Playground.cs** — the body sandbox around the table (east climbing/mantling, west physics toys, south
   crawl/duck/door); dynamic pieces are "prop"s reset by the menu's Reset props. `tools/playground_shots.tscn` renders
   overview PNGs (`godot-mono --path . tools/playground_shots.tscn -- <dir>`).
@@ -388,7 +392,7 @@ Floor StaticBody mask 1|3|4|5 (collision_mask 29).
 ## 5. Known issues / open questions
 
 - **Ragdoll player (step 2.1) — owner playtested step 2 ("feels amazing for the most part"); 2.1 fixes are
-  unvalidated in-headset.** Remaining gaps: shoulder has no cone limit (fork addition); strength values are
+  unvalidated in-headset; 2.1 was unstable in the headset, 2.2 fixes it — see research "Step 2.2".** Remaining gaps: shoulder has no cone limit (fork addition); strength values are
   human-scale guesses (menu slider); stick-crawling is a comfort concession (Nimso pulls with hands only); legs are
   visual only. Legacy spikes (arm/grab/body/collapse) pin 90 Hz because the chase bodies were tuned there.
 

research/ragdoll-player-step2.md

@@ -92,3 +92,42 @@ Changes and the measured reasons:
 Ground steeper than `MaxSlopeDegrees` 35° gives no support, so the 40° ramp can't be walked up; the 18° one can.
 Still open: the shoulder cone limit (needs a fork addition). `tools/playground_shots.tscn` renders overview PNGs for
 layout checks.
+
+## Step 2.2 — the 2.1 playtest was unstable; root causes (2026-10-02)
+
+The owner reported everything "all over the place":
+- Mantling swung the chest out of control and the hands "wobbled more and more".
+- Crouching made the body slide around and spin.
+- Nothing static was grabbable.
+- The steep ramp slipped the body out from under them.
+
+RagdollSpike passed all of it, because its input was IDEAL: smooth poses every 144 Hz tick, no jitter. Fixes:
+
+1. **The spike now runs on REAL input by default**: tracking sample-and-hold at 90 Hz under 144 Hz physics, plus
+   0.5 mm / 0.1° jitter per sample (`-- ideal` / `nonoise` / `nohold` isolate the factors). Lesson: a body-physics
+   test with perfect input proves nothing about the headset.
+2. **`PoseFilter` + `RagdollDriver`** (`scripts/RagdollDriver.cs`). Tracked poses are timestamped per new sample
+   and extrapolated between samples in play-space-local coordinates. One driver runs the tick pipeline for
+   both `PlayerRig` and the spike, so the test runs the game's code path.
+3. **Low-pass every feed-forward**: muscles/elbow τ 0.05 s, ground control τ 0.12 s. Ground control's velocity
+   term multiplies by the whole body mass, so 1.5 mm of jitter became hundreds of newtons of buzz (pelvis
+   0.27 → 0.04 m/s at rest).
+4. **Arm muscles stay LOCAL to the chest's target pose.** 2.1 aimed them in the physical chest frame, which closes a
+   rotation feedback loop: the chest turns, the world-fixed arm targets push back on the chest, and the chest turns
+   further. Jitter excited it into a slow twist (eye drifting 15 cm): the mantle "chest slipping". Only a
+   horizontal translation of the reach is kept (body held back from the camera).
+5. **Structural hand strength only when the hand pushes on or holds something.** A hand reaching past its arm's
+   length into free air pulled the whole body down by up to 400 N (crouch: eye 11 cm off).
+6. **No free-path view chasing while grounded.** Any eye/camera mismatch (crouch poses can't match exactly) moved
+   the view, the pose target followed, the body followed, and so on: an 8 m slide while holding a crouch. The view
+   is now only pushed back when geometry blocks the head. Instead, the stick stops pushing in the direction the
+   body is held back (`PlayerRagdoll.HeldBack`, `PlayerRig.HoldBack`).
+7. **Explicit inertia on the `Legs` body.** Disabling its only collision shape (tuck) left it with no rotational
+   inertia; its 400 N·m drive then tumbled the pelvis forward, which flipped the "yaw". This was the crouch spin.
+   Rule: a body whose shapes can all be disabled needs explicit `Inertia`.
+8. **World grabs: the Box3D wrapper returns a null `collider` from `IntersectShape`**, only `collider_id`. Resolve it
+   with `GodotObject.InstanceFromId`. The grab sphere is now 7 cm, checked at the palm and then the hand centre.
+   The spike asserts the game's own `PropGrabber.WorldUnderPalm` finds the bar.
+
+New spike phases: hold a crouch (eyes 1.0 m) and a deep crouch (0.7 m) without drift (< 5 cm) or spin (< 5°),
+eye on camera (< 5 cm). 29 phases total, all on real input.

scripts/PlayerRagdoll.cs

@@ -29,6 +29,10 @@ public partial class PlayerRagdoll : Node3D
     public const float ShoulderKp = 20f, ShoulderTorque = 45f;    // ~human shoulder flexion strength
     public const float ElbowKp = 20f, ElbowTorque = 45f;
     public const float MuscleMaxSpin = 15f;
+    // Feed-forwards are derivatives of tracking: low-pass them or tracking jitter (±1–2 mm per
+    // sample) becomes hundreds of newtons of buzz (RagdollSpike REAL input mode).
+    public const float MuscleFeedForwardTau = 0.05f;   // s
+    public const float GroundFeedForwardTau = 0.12f;   // s
     public const float GirdleKp = 30f, GirdleForce = 2000f;  // shoulder drive, linear part
     // Hand guide (chest→hand drive): pulls the hand onto the controller; capped so the arm,
     // not the guide, carries real loads.
@@ -67,7 +71,7 @@ public partial class PlayerRagdoll : Node3D
     public const float AirBalanceShare = 0.3f;
     // Play-space reconciliation.
     public const float CameraRadius = 0.03f;           // sphere swept from the head's eye to the camera
-    public const float FreeSlack = 0.2f;               // camera may lead an unobstructed (lagging/held) head by this much
+    public const float FreeSlack = 0.2f;               // camera leading the body's eye by more than this = body held back: stick stops pushing that way
     public const float AirSlack = 0.05f;               // climbing/hanging (braced): the view rides the body tightly
     public const float FallSlack = 0.25f;              // free airborne: brief ground loss (sliding off a steep slope) mustn't sink the view
     public const float GroundFollowRate = 8f;
@@ -96,6 +100,7 @@ public partial class PlayerRagdoll : Node3D
         public float Kp;
         public Quaternion PrevTarget;
         public bool HasPrev;
+        public Vector3 Ff;
     }
 
     private sealed class Drive
@@ -105,6 +110,7 @@ public partial class PlayerRagdoll : Node3D
         public Vector3 AnchorA, AnchorB;    // anchor point, parent-local / child-local
         public Quaternion PrevTarget;
         public bool HasPrev;
+        public Vector3 Ff;
     }
 
     private sealed class Arm
@@ -115,6 +121,7 @@ public partial class PlayerRagdoll : Node3D
         public Drive Shoulder, Guide;
         public float UpperLen, ForeLen;
         public float PrevFlexTarget = -1f;
+        public float FlexFf;
         public float GuideCap = HandGuideForce;
         public PhysicsBody3D Held;
     }
@@ -126,6 +133,9 @@ public partial class PlayerRagdoll : Node3D
     public bool Grounded { get; private set; }
     public float GroundY => _footY;
     public bool Braced { get; private set; }             // a hand touches or holds static world
+    // Horizontal direction in which the body is held back from the camera (zero if not): the stick
+    // must not keep moving the play space that way.
+    public Vector3 HeldBack { get; private set; }
     // Really climbing: a hand holds static world, or the arms are lifting the body (mantle).
     public bool Climbing => Built && (_arms[0].Held is StaticBody3D || _arms[1].Held is StaticBody3D || _lifted);
     public RigidBody3D Legs { get; private set; }
@@ -144,6 +154,9 @@ public partial class PlayerRagdoll : Node3D
     private readonly Vector3[] _girdle = new Vector3[2];  // True Body shoulder offset, chest frame
     private float _footY;
     private float _supportGoalY;
+    private Vector3 _goalVelocity;
+
+    private static float LowPass(float dt, float tau) => 1f - Mathf.Exp(-dt / tau);
     private bool _lifted;
     private float _legsHeight;
     private Drive _legsDrive;
@@ -198,6 +211,10 @@ public partial class PlayerRagdoll : Node3D
         _legsHeight = Mathf.Max(0.2f, standingHip - MaxStepHeight);
         Legs = MakeBody("Legs", new BoxShape3D { Size = new Vector3(0.28f * s, _legsHeight, 0.2f * s) }, LegsMass, BodyLayer, WorldMask, pants,
             c * new Transform3D(Basis.Identity, hip - new Vector3(0f, _legsHeight * 0.5f, 0f)), visible: false);
+        // Explicit inertia: the collider is switched off when tucked, and a body without an
+        // enabled shape has no inertia — its 400 N·m drive then tumbled the whole pelvis
+        // (owner 2.1 "body spinning" when crouched).
+        Legs.Inertia = new Vector3(_legsHeight * _legsHeight + 0.04f, 0.28f * 0.28f + 0.04f, _legsHeight * _legsHeight + 0.08f) * (LegsMass / 12f);
         _footY = pose.Eye.Y - p.EyeHeight;
         Chest = MakeBody("Chest", new BoxShape3D { Size = chestSize }, 0.216f * m, BodyLayer, WorldMask, shirt,
             c * new Transform3D(Basis.Identity, lumbar + _chestCenterLocal));
@@ -428,18 +445,23 @@ public partial class PlayerRagdoll : Node3D
                 // real hand. Vertically a sagging body keeps its arm pose (the aim point moves with
                 // the shoulder), so straight real arms stay straight virtual arms — pillars that hold
                 // you up when crawling or press you up a ledge (the hand guide adds the rest).
+                // Only a horizontal TRANSLATION of the reach: solved in the chest TARGET frame (the
+                // muscles stay local). Aiming in the physical chest frame made the shoulder muscles
+                // feed chest rotation back into the chest — a slow twist that tracking jitter
+                // excited into "chest slipping out of control" (owner playtest 2.1).
                 Transform3D chestPhys = Chest.GlobalTransform.Orthonormalized();
                 Vector3 shPhys = chestPhys * (a.Shoulder.AnchorA + _girdle[side]);
+                Vector3 held = shPhys - sh;
+                held.Y = 0f;
                 Transform3D ctrl = _targets[a.Hand];
-                Vector3 aim = ctrl * new Vector3(0f, 0f, WristOffset) + Vector3.Up * (shPhys.Y - sh.Y);
                 ArmSolver solver = _armSolvers[side];
-                solver.Solve(shPhys, aim, chestPhys.Basis, chestPhys.Basis.X * (side == 0 ? -1f : 1f),
+                solver.Solve(sh, ctrl * new Vector3(0f, 0f, WristOffset) - held, chest, chest.X * (side == 0 ? -1f : 1f),
                     ctrl.Basis, a.UpperLen, a.ForeLen, dt);
-                Vector3 d = solver.Wrist - shPhys;
+                Vector3 d = solver.Wrist - sh;
-                Vector3 h = d.LengthSquared() > 1e-8f ? solver.Pole.Cross(d.Normalized()) : chestPhys.Basis.X;
+                Vector3 h = d.LengthSquared() > 1e-8f ? solver.Pole.Cross(d.Normalized()) : chest.X;
-                h = h.LengthSquared() > 1e-8f ? h.Normalized() : chestPhys.Basis.X;
+                h = h.LengthSquared() > 1e-8f ? h.Normalized() : chest.X;
-                Vector3 u = (solver.Elbow - shPhys).Normalized(), f = (solver.Wrist - solver.Elbow).Normalized();
+                Vector3 u = (solver.Elbow - sh).Normalized(), f = (solver.Wrist - solver.Elbow).Normalized();
-                _targets[a.Upper] = new Transform3D(BoneBasis(u, h), shPhys + u * (a.UpperLen * 0.5f));
+                _targets[a.Upper] = new Transform3D(BoneBasis(u, h), sh + u * (a.UpperLen * 0.5f));
                 _targets[a.Fore] = new Transform3D(BoneBasis(f, h), solver.Elbow + f * (a.ForeLen * 0.5f));
             }
         }
@@ -502,10 +524,11 @@ public partial class PlayerRagdoll : Node3D
         Quaternion current = (Rot(b.Parent) * b.FrameA).Inverse() * (Rot(b.Child) * b.FrameB);
         Quaternion target = (parentTarget.Orthonormalized().GetRotationQuaternion() * b.FrameA).Inverse()
             * (childTarget.Orthonormalized().GetRotationQuaternion() * b.FrameB);
-        Vector3 ff = b.HasPrev && dt > 0f ? (BodyMath.RotationError(target, b.PrevTarget) / dt).LimitLength(MuscleMaxSpin) : Vector3.Zero;
+        Vector3 raw = b.HasPrev && dt > 0f ? (BodyMath.RotationError(target, b.PrevTarget) / dt).LimitLength(MuscleMaxSpin) : Vector3.Zero;
+        b.Ff = b.Ff.Lerp(raw, LowPass(dt, MuscleFeedForwardTau));
         b.PrevTarget = target;
         b.HasPrev = true;
-        Vector3 w = (ff + BodyMath.RotationError(target, current) * b.Kp).LimitLength(MuscleMaxSpin);
+        Vector3 w = (b.Ff + BodyMath.RotationError(target, current) * b.Kp).LimitLength(MuscleMaxSpin);
         SetAngularVelocity(b.Joint, w);
     }
 
@@ -537,9 +560,10 @@ public partial class PlayerRagdoll : Node3D
         int side = a == _arms[0] ? 0 : 1;
         Vector3 up = _targets[a.Upper].Basis.Y, fore = _targets[a.Fore].Basis.Y;
         float target = Mathf.Acos(Mathf.Clamp(up.Dot(fore), -1f, 1f));
-        float ff = a.PrevFlexTarget >= 0f && dt > 0f ? Mathf.Clamp((target - a.PrevFlexTarget) / dt, -MuscleMaxSpin, MuscleMaxSpin) : 0f;
+        float raw = a.PrevFlexTarget >= 0f && dt > 0f ? Mathf.Clamp((target - a.PrevFlexTarget) / dt, -MuscleMaxSpin, MuscleMaxSpin) : 0f;
+        a.FlexFf = Mathf.Lerp(a.FlexFf, raw, LowPass(dt, MuscleFeedForwardTau));
         a.PrevFlexTarget = target;
-        float w = Mathf.Clamp(ff + (target - ElbowFlex(side)) * ElbowKp, -MuscleMaxSpin, MuscleMaxSpin);
+        float w = Mathf.Clamp(a.FlexFf + (target - ElbowFlex(side)) * ElbowKp, -MuscleMaxSpin, MuscleMaxSpin);
         a.Elbow.SetParam(HingeJoint3D.Param.MotorTargetVelocity, HingeSign * w);
     }
 
@@ -622,13 +646,15 @@ public partial class PlayerRagdoll : Node3D
         SetLinearVelocity(d.Joint, frameA.Inverse() * (err * GirdleKp));
 
         Quaternion current = frameA.Inverse() * (Rot(a.Upper) * d.FrameB);
-        // Arm targets are solved from the physical chest, so the physical chest is the parent frame.
+        // Local muscle: relative to the chest's TARGET pose (never to the physical chest — that
-        Quaternion target = (chest.Basis.GetRotationQuaternion() * d.FrameA).Inverse()
+        // closes a rotation feedback loop through the arms).
+        Quaternion target = (_targets[Chest].Basis.Orthonormalized().GetRotationQuaternion() * d.FrameA).Inverse()
             * (_targets[a.Upper].Basis.Orthonormalized().GetRotationQuaternion() * d.FrameB);
-        Vector3 ff = d.HasPrev && dt > 0f ? (BodyMath.RotationError(target, d.PrevTarget) / dt).LimitLength(MuscleMaxSpin) : Vector3.Zero;
+        Vector3 raw = d.HasPrev && dt > 0f ? (BodyMath.RotationError(target, d.PrevTarget) / dt).LimitLength(MuscleMaxSpin) : Vector3.Zero;
+        d.Ff = d.Ff.Lerp(raw, LowPass(dt, MuscleFeedForwardTau));
         d.PrevTarget = target;
         d.HasPrev = true;
-        SetAngularVelocity(d.Joint, (ff + BodyMath.RotationError(target, current) * ShoulderKp).LimitLength(MuscleMaxSpin));
+        SetAngularVelocity(d.Joint, (d.Ff + BodyMath.RotationError(target, current) * ShoulderKp).LimitLength(MuscleMaxSpin));
     }
 
     // Force-capped pull of the hand onto the controller, reacting into the chest (arm muscles).
@@ -645,6 +671,10 @@ public partial class PlayerRagdoll : Node3D
         // Axial share of the error, with a 3 cm floor so a nearly-reached target's noisy error
         // direction can't flip a held load into "structural".
         float align = axis.LengthSquared() > 1e-8f ? Mathf.Abs(err.Dot(axis.Normalized())) / (err.Length() + StructuralDeadband) : 0f;
+        // Structure only helps against something: a hand in free air reaching past its arm's
+        // length must not haul the whole body after it.
+        if (a.Held == null && a.Hand.GetContactCount() == 0)
+            align = 0f;
         float cap = Mathf.Lerp(HandGuideForce, HandStructuralForce, align) * Mathf.Max(0.05f, Strength);
         if (Mathf.Abs(cap - a.GuideCap) > 1f)
         {
@@ -701,11 +731,13 @@ public partial class PlayerRagdoll : Node3D
         // ground, the pose target and the ground offset move by the same amount in opposite
         // directions — differentiating the pose alone would launch the body.
         Vector3 goalNow = target.Origin + Vector3.Up * (_footY - floorY);
-        Vector3 targetVelocity = _havePelvisPrev && dt > 0f ? (goalNow - _pelvisTargetPrev) / dt : Vector3.Zero;
+        Vector3 rawVelocity = _havePelvisPrev && dt > 0f ? (goalNow - _pelvisTargetPrev) / dt : Vector3.Zero;
         _pelvisTargetPrev = goalNow;
         _havePelvisPrev = true;
-        if (targetVelocity.Length() > 10f)
+        if (rawVelocity.Length() > 10f)
-            targetVelocity = Vector3.Zero;
+            rawVelocity = Vector3.Zero;
+        _goalVelocity = _goalVelocity.Lerp(rawVelocity, LowPass(dt, GroundFeedForwardTau));
+        Vector3 targetVelocity = _goalVelocity;
 
         float weight = BodyMass * 9.8f;
         if (Grounded)
@@ -778,13 +810,20 @@ public partial class PlayerRagdoll : Node3D
                 if (!Climbing)
                     correction.Y = 0f;
             }
-            else
+            else if (!Grounded)
             {
-                float slack = Grounded ? FreeSlack : Climbing ? AirSlack : FallSlack;
+                // Free path: the view never chases the body while standing — any pose mismatch
-                if (lead.Length() > slack)
+                // (a crouch the body can't match exactly) would otherwise walk the play space away
-                    correction = -lead * (1f - slack / lead.Length());
+                // forever (body → view → pose target → body; owner 2.1 "sliding around").
+                // Airborne it rides the body: vertically in a fall, fully while climbing.
+                Vector3 follow = Climbing ? lead : new Vector3(0f, lead.Y, 0f);
+                float slack = Climbing ? AirSlack : FallSlack;
+                if (follow.Length() > slack)
+                    correction = -follow * (1f - slack / follow.Length());
             }
         }
+        Vector3 flatLead = new(lead.X, 0f, lead.Z);
+        HeldBack = flatLead.Length() > FreeSlack ? flatLead.Normalized() : Vector3.Zero;
         if (Grounded)
         {
             correction.Y = 0f;

scripts/PlayerRig.cs

@@ -33,9 +33,9 @@ public partial class PlayerRig : Node
     private bool _haveLastOrigin;
     private Vector3 _moveVelocity;
     private bool _snapArmed = true;
-    private readonly Vector3[] _ctrlPrev = new Vector3[2];
     private readonly MeshInstance3D[] _ghosts = new MeshInstance3D[2];
     private bool _rebuild = true;
+    private RagdollDriver _driver;
 
     public PlayerRagdoll Ragdoll => _ragdoll;
     public static bool Spectator { get; private set; }
@@ -84,6 +84,7 @@ public partial class PlayerRig : Node
         // frame); the body is simulated, so it interpolates.
         _ragdoll = new PlayerRagdoll { Name = "Ragdoll", PhysicsInterpolationMode = PhysicsInterpolationModeEnum.On };
         AddChild(_ragdoll);
+        _driver = new RagdollDriver { Solver = Solver, Ragdoll = _ragdoll };
         BodyProfile.Changed += _ => _rebuild = true;
         for (int i = 0; i < 2; i++)
         {
@@ -121,30 +122,16 @@ public partial class PlayerRig : Node
         if (_haveLastOrigin && _ragdoll.Built && IsJump(_lastOrigin, origin))
             Carry(origin * _lastOrigin.AffineInverse());
 
-        if (_ragdoll.Built && !_rebuild)
+        // 2. Stick locomotion.
-        {
+        if (_ragdoll.Built && !_driver.RebuildRequested)
-            // 2. Stick locomotion, 3. reconciliation.
             Locomote(dt);
-            Vector3 correction = _ragdoll.OriginCorrection(_camera.GlobalPosition, _origin.GlobalPosition.Y, dt);
-            if (correction != Vector3.Zero)
-                _origin.GlobalPosition += correction;
-        }
 
-        // 4. Pose + muscles.
+        // 3. Filtered tracking → play-space correction → True Body → muscles (shared with RagdollSpike).
-        Transform3D head = _camera.GlobalTransform;
+        _driver.RebuildRequested |= _rebuild;
-        Transform3D left = _left.GlobalTransform, right = _right.GlobalTransform;
+        _rebuild = false;
-        Solver.Solve(profile, head, left, right, _origin.GlobalPosition.Y, dt);
+        Transform3D o = _origin.GlobalTransform;
-        if (_rebuild || !_ragdoll.Built)
+        _driver.Tick(profile, ref o, _camera.Transform, _left.Transform, _right.Transform, _moveVelocity, dt);
-        {
+        _origin.GlobalTransform = o;
-            _ragdoll.Build(profile, Solver, left, right);
-            _rebuild = false;
-            _ctrlPrev[0] = left.Origin;
-            _ctrlPrev[1] = right.Origin;
-        }
-        Vector3 lv = (left.Origin - _ctrlPrev[0]) / dt, rv = (right.Origin - _ctrlPrev[1]) / dt;
-        _ctrlPrev[0] = left.Origin;
-        _ctrlPrev[1] = right.Origin;
-        _ragdoll.Step(Solver, left, right, lv, rv, _origin.GlobalPosition.Y, dt);
         _lastOrigin = _origin.GlobalTransform;
         _haveLastOrigin = true;
     }
@@ -162,6 +149,14 @@ public partial class PlayerRig : Node
         }
     }
 
+    // The body is held back (hips against a table, a wall the head clears): stop the stick from
+    // carrying the view further that way.
+    public static Vector3 HoldBack(Vector3 velocity, Vector3 heldBack)
+    {
+        float into = velocity.Dot(heldBack);
+        return into > 0f ? velocity - heldBack * into : velocity;
+    }
+
     private static bool IsJump(Transform3D a, Transform3D b) =>
         a.Origin.DistanceTo(b.Origin) > JumpDistance ||
         BodyMath.RotationError(b.Basis.GetRotationQuaternion(), a.Basis.GetRotationQuaternion()).Length() > JumpAngle;
@@ -170,8 +165,6 @@ public partial class PlayerRig : Node
     {
         _ragdoll.TeleportBy(delta);
         Solver.Shift(delta);
-        _ctrlPrev[0] = delta * _ctrlPrev[0];
-        _ctrlPrev[1] = delta * _ctrlPrev[1];
     }
 
     private void Locomote(float dt)
@@ -195,6 +188,7 @@ public partial class PlayerRig : Node
         if (!_ragdoll.Grounded)
             desired = _moveVelocity;  // no air control
         _moveVelocity = _moveVelocity.MoveToward(desired, MoveAcceleration * dt);
+        _moveVelocity = HoldBack(_moveVelocity, _ragdoll.HeldBack);
         if (_moveVelocity != Vector3.Zero)
             _origin.GlobalPosition += _moveVelocity * dt;
 

scripts/PropGrabber.cs

@@ -11,7 +11,7 @@ public partial class PropGrabber : Node
     private const float BreakTime = 0.25f;
     private const float BreakDistanceBoth = 0.4f;
     private const float GripRipDistance = 0.8f;
-    private const float WorldGrabRadius = 0.05f;   // palm sphere for grabbing static world (ledges, bars, holds)
+    private const float WorldGrabRadius = 0.07f;   // palm sphere for grabbing static world (ledges, bars, holds)
     public const string NoGrabGroup = "no_grab";   // static bodies that can't be grabbed (the floor)
 
     private static PropGrabber _instance;
@@ -197,7 +197,7 @@ public partial class PropGrabber : Node
         _breakTimer[hand] = 0f;
     }
 
-    private static Vector3 PalmPoint(RigidBody3D handBody, int hand) =>
+    public static Vector3 PalmPoint(RigidBody3D handBody, int hand) =>
         handBody.GlobalPosition + handBody.GlobalTransform.Basis * new Vector3(PalmOffset(hand), 0f, 0f);
 
     private static float PalmOffset(int hand) => hand == 0 ? PalmGrabOffset : -PalmGrabOffset;
@@ -214,11 +214,12 @@ public partial class PropGrabber : Node
         nearest = NearestProp(handBody.GlobalPosition, CenterGrabRadius);
         if (nearest != null)
             return nearest;
-        return WorldUnderPalm(palm, handBody.GetWorld3D());
+        return WorldUnderPalm(palm, handBody.GetWorld3D()) ?? WorldUnderPalm(handBody.GlobalPosition, handBody.GetWorld3D());
     }
 
-    // Climbing: any static body touching the palm (except the "no_grab" group) can be held.
+    // Climbing: any static body near the palm (except the "no_grab" group) can be held.
-    private static StaticBody3D WorldUnderPalm(Vector3 palm, World3D world)
+    // NOTE (Box3D wrapper): shape-query results carry a null "collider" — resolve "collider_id".
+    public static StaticBody3D WorldUnderPalm(Vector3 palm, World3D world)
     {
         PhysicsShapeQueryParameters3D query = new()
         {
@@ -228,7 +229,7 @@ public partial class PropGrabber : Node
         };
         foreach (Godot.Collections.Dictionary hit in world.DirectSpaceState.IntersectShape(query, 8))
         {
-            if (hit["collider"].AsGodotObject() is StaticBody3D body && !body.IsInGroup(NoGrabGroup))
+            if (GodotObject.InstanceFromId((ulong)hit["collider_id"]) is StaticBody3D body && !body.IsInGroup(NoGrabGroup))
                 return body;
         }
         return null;

scripts/RagdollDriver.cs

@@ -0,0 +1,93 @@
+using Godot;
+
+// Smooths one tracked pose for the physics tick. Tracking updates at the display rate (90 Hz) but
+// physics runs at 144 Hz: sampled raw, every second or third tick sees the pose frozen and the next
+// one jumped, and every velocity feed-forward downstream (muscles, hand guides, ground control)
+// turns that into jerks — the step-2.1 "wobbling more and more / sliding around" in the headset.
+// Each new sample is timestamped; between samples the pose is extrapolated with the (smoothed)
+// sample velocity. Works in the PLAY-SPACE-LOCAL frame, so moving the origin never looks like motion.
+public sealed class PoseFilter
+{
+    public const float MaxExtrapolation = 1.5f / 90f;  // s
+    public const float VelocitySmoothing = 0.3f;       // EMA weight of each new sample
+    public const float JumpDistance = 0.5f;            // m between samples = recenter, not motion
+
+    private Transform3D _last;
+    private double _tLast;
+    private bool _has;
+
+    public Vector3 Velocity { get; private set; }         // play-space-local m/s
+    public Vector3 AngularVelocity { get; private set; }  // play-space-local rad/s
+
+    public void Reset() => _has = false;
+
+    public Transform3D Sample(Transform3D raw, double now)
+    {
+        if (!_has)
+        {
+            _has = true;
+            _last = raw;
+            _tLast = now;
+            Velocity = AngularVelocity = Vector3.Zero;
+            return raw;
+        }
+        if (raw != _last)
+        {
+            float interval = (float)(now - _tLast);
+            if (interval > 1e-4f)
+            {
+                if (raw.Origin.DistanceTo(_last.Origin) > JumpDistance)
+                {
+                    Velocity = AngularVelocity = Vector3.Zero;
+                }
+                else
+                {
+                    Vector3 v = (raw.Origin - _last.Origin) / interval;
+                    Vector3 w = BodyMath.RotationError(raw.Basis.GetRotationQuaternion(), _last.Basis.GetRotationQuaternion()) / interval;
+                    Velocity = Velocity.Lerp(v, VelocitySmoothing);
+                    AngularVelocity = AngularVelocity.Lerp(w, VelocitySmoothing);
+                }
+            }
+            _last = raw;
+            _tLast = now;
+        }
+        float age = Mathf.Min((float)(now - _tLast), MaxExtrapolation);
+        Basis spin = AngularVelocity.LengthSquared() > 1e-10f
+            ? new Basis(AngularVelocity.Normalized(), AngularVelocity.Length() * age) : Basis.Identity;
+        return new Transform3D(spin * _last.Basis.Orthonormalized(), _last.Origin + Velocity * age);
+    }
+}
+
+// The per-physics-tick body pipeline, shared by PlayerRig (headset) and RagdollSpike so the
+// regression runs exactly what the game runs: filter the tracked poses → play-space correction
+// (push-back / ground follow / falls) → True Body solve → (re)build → ragdoll muscles.
+// Locomotion (moving the origin by the stick, turning, teleports) happens before Tick.
+public sealed class RagdollDriver
+{
+    public readonly PoseFilter Head = new(), Left = new(), Right = new();
+    public TrueBodySolver Solver;
+    public PlayerRagdoll Ragdoll;
+    public bool RebuildRequested = true;
+    private double _now;
+
+    // origin = play space (modified by the correction); raw* = origin-local tracked poses as last
+    // reported (repeat between tracking updates); moveVelocity = intended origin velocity (stick),
+    // the only origin motion that is real hand motion for the guides' feed-forward.
+    public void Tick(BodyProfile profile, ref Transform3D origin, Transform3D rawHead, Transform3D rawLeft, Transform3D rawRight,
+        Vector3 moveVelocity, float dt)
+    {
+        _now += dt;
+        Transform3D head = Head.Sample(rawHead, _now), left = Left.Sample(rawLeft, _now), right = Right.Sample(rawRight, _now);
+        if (Ragdoll.Built && !RebuildRequested)
+            origin.Origin += Ragdoll.OriginCorrection((origin * head).Origin, origin.Origin.Y, dt);
+        Transform3D h = origin * head, l = origin * left, r = origin * right;
+        Solver.Solve(profile, h, l, r, origin.Origin.Y, dt);
+        if (RebuildRequested || !Ragdoll.Built)
+        {
+            Ragdoll.Build(profile, Solver, l, r);
+            RebuildRequested = false;
+        }
+        Vector3 lv = origin.Basis * Left.Velocity + moveVelocity, rv = origin.Basis * Right.Velocity + moveVelocity;
+        Ragdoll.Step(Solver, l, r, lv, rv, origin.Origin.Y, dt);
+    }
+}

scripts/RagdollSpike.cs

@@ -23,8 +23,6 @@ public partial class RagdollSpike : Node3D
     private Transform3D _origin = Transform3D.Identity;
     private Transform3D _headLocal, _leftLocal, _rightLocal;
     private Vector3 _stickVelocity;
-    private Vector3 _prevL, _prevR;
-    private bool _needBuild;
 
     // Measurements (reset per phase).
     private float _maxEyeErr, _maxHandErr, _endHandErr, _maxSpeed, _minCamZ, _minEyeZ, _maxElbowErr;
@@ -32,13 +30,49 @@ public partial class RagdollSpike : Node3D
     private int _snapsAtStart;
     private float _measureFrom;
 
-    private Transform3D Camera => _origin * _headLocal;
+    // What the ragdoll sees. REAL-INPUT mode (default; `-- ideal` disables it) reproduces the headset:
-    private Transform3D Left => _origin * _leftLocal;
+    // tracking poses update at the 90 Hz display rate (sample-and-hold between 144 Hz physics ticks)
-    private Transform3D Right => _origin * _rightLocal;
+    // with a little jitter — the smooth per-tick input of the ideal mode hid the 2.1 instabilities.
+    private Transform3D Camera => _origin * Tracked(0, _headLocal);
+    private Transform3D Left => _origin * Tracked(1, _leftLocal);
+    private Transform3D Right => _origin * Tracked(2, _rightLocal);
+
+    private bool _realInput = true, _noiseOn = true, _holdOn = true;
+    private const float TrackingHz = 90f;
+    private readonly Transform3D[] _held = new Transform3D[3];
+    private readonly long[] _heldFrame = { -1, -1, -1 };
+    private readonly RandomNumberGenerator _noise = new() { Seed = 3 };
+    private float _clock;
+
+    private Transform3D Tracked(int i, Transform3D truth)
+    {
+        if (!_realInput)
+            return truth;
+        long frame = _holdOn ? (long)(_clock * TrackingHz) : (long)(_clock * 100000f);
+        if (frame != _heldFrame[i])
+        {
+            _heldFrame[i] = frame;
+            float p = _noiseOn ? 0.0005f : 0f, r = _noiseOn ? Mathf.DegToRad(0.1f) : 0f;   // pessimistic for inside-out tracking
+            Vector3 dp = new(_noise.Randfn(0f, p), _noise.Randfn(0f, p), _noise.Randfn(0f, p));
+            Basis dr = Basis.FromEuler(new Vector3(_noise.Randfn(0f, r), _noise.Randfn(0f, r), _noise.Randfn(0f, r)));
+            _held[i] = new Transform3D(dr * truth.Basis, truth.Origin + dp);
+        }
+        return _held[i];
+    }
 
     public override void _Ready()
     {
         _profile = BodyProfile.Estimate(EyeHeight);
+        foreach (string arg in OS.GetCmdlineUserArgs())
+        {
+            if (arg == "ideal")
+                _realInput = false;
+            if (arg == "nonoise")
+                _noiseOn = false;
+            if (arg == "nohold")
+                _holdOn = false;
+        }
+        GD.Print($"RAGDOLL: input mode {(_realInput ? "REAL (90 Hz tracking, jitter)" : "ideal")} at {Engine.PhysicsTicksPerSecond} Hz physics");
         AddChild(MakeStatic(new Vector3(40f, 1f, 40f), new Vector3(0f, -0.5f, 0f), 29));
         _ragdoll = new PlayerRagdoll { Name = "Ragdoll" };
         AddChild(_ragdoll);
@@ -65,6 +99,8 @@ public partial class RagdollSpike : Node3D
         _phases.Add(("two-handed pull-up on a grabbed bar", () => SetupBarHang(), t => TickPullUp(both: true), 3.5f, () => FinishPullUp(true)));
         _phases.Add(("one-handed pull-up is weaker", () => SetupBarHang(), t => TickPullUp(both: false), 3.5f, () => FinishPullUp(false)));
         _phases.Add(("crawls through a 0.6 m tunnel", SetupTunnel, TickCrawl, 7f, FinishCrawl));
+        _phases.Add(("holds a crouch (eyes 1.0 m) without sliding or spinning", Rest, t => TickCrouchHold(1.0f), 5f, FinishCrouchHold));
+        _phases.Add(("holds a deep crouch (eyes 0.7 m) without sliding or spinning", Rest, t => TickCrouchHold(0.7f), 5f, FinishCrouchHold));
         _phases.Add(("walks off a 1 m ledge and lands", SetupLedgeTop, _ => _stickVelocity = _t > 0.5f && _t < 2f ? new Vector3(0f, 0f, -1.2f) : Vector3.Zero, 4f, FinishDrop));
         _phases.Add(("walks up an 18° ramp", () => SetupRamp(18f), _ => _stickVelocity = new Vector3(0f, 0f, -1.2f), 4f, () => FinishRamp(true)));
         _phases.Add(("can't walk up a 40° ramp", () => SetupRamp(40f), _ => _stickVelocity = new Vector3(0f, 0f, -1.2f), 4f, () => FinishRamp(false)));
@@ -79,6 +115,7 @@ public partial class RagdollSpike : Node3D
             return;
         float dt = (float)delta;
         _t += dt;
+        _clock += dt;
         _phases[_phase].Tick(dt);
         if (_phase > 0)
             Drive(dt);
@@ -116,24 +153,34 @@ public partial class RagdollSpike : Node3D
     // Exactly PlayerRig's tick order.
     private void Drive(float dt)
     {
-        _origin.Origin += _stickVelocity * dt;
+        _driver ??= new RagdollDriver { Solver = _solver, Ragdoll = _ragdoll };
-        if (_ragdoll.Built && !_needBuild)
+        Vector3 stick = _ragdoll.Built && !_needBuild ? PlayerRig.HoldBack(_stickVelocity, _ragdoll.HeldBack) : _stickVelocity;
-            _origin.Origin += _ragdoll.OriginCorrection(Camera.Origin, _origin.Origin.Y, dt);
+        _origin.Origin += stick * dt;
-        _solver.Solve(_profile, Camera, Left, Right, _origin.Origin.Y, dt);
+        _driver.Tick(_profile, ref _origin, Tracked(0, _headLocal), Tracked(1, _leftLocal), Tracked(2, _rightLocal), _stickVelocity, dt);
-        if (_needBuild)
-        {
-            _ragdoll.Build(_profile, _solver, Left, Right);
-            _needBuild = false;
-            _prevL = Left.Origin;
-            _prevR = Right.Origin;
-        }
-        Vector3 lv = (Left.Origin - _prevL) / dt, rv = (Right.Origin - _prevR) / dt;
-        _prevL = Left.Origin;
-        _prevR = Right.Origin;
-        _ragdoll.Step(_solver, Left, Right, lv, rv, _origin.Origin.Y, dt);
         Measure();
     }
 
+    private RagdollDriver _driver;
+    private bool _needBuild
+    {
+        get => _driver == null || _driver.RebuildRequested;
+        set
+        {
+            _driver ??= new RagdollDriver { Solver = _solver, Ragdoll = _ragdoll };
+            _driver.RebuildRequested = value;
+            if (value)
+            {
+                // New phase: resample tracking now (a held sample from the last phase would build
+                // the body where the previous phase left the head).
+                for (int i = 0; i < 3; i++)
+                    _heldFrame[i] = -1;
+                _driver.Head.Reset();
+                _driver.Left.Reset();
+                _driver.Right.Reset();
+            }
+        }
+    }
+
     private void Measure()
     {
         foreach (RigidBody3D b in _ragdoll.Bodies)
@@ -224,8 +271,10 @@ public partial class RagdollSpike : Node3D
 
     private bool FinishStand()
     {
+        float core = Mathf.Max(_ragdoll.Pelvis.LinearVelocity.Length(), Mathf.Max(_ragdoll.Chest.LinearVelocity.Length(), _ragdoll.Head.LinearVelocity.Length()));
+        GD.Print($"RAGDOLL:   body core speed at rest {core:F3} m/s (limit 0.03)");
         GD.Print($"RAGDOLL:   eye error max {_maxEyeErr:F3} m, hand error max {_maxHandErr:F3} m, elbow error max {Mathf.RadToDeg(_maxElbowErr):F1}°, end speed {_maxSpeed:F3} m/s, grounded {_ragdoll.Grounded}, snaps {NewSnaps}, pelvis y {_ragdoll.Pelvis.GlobalPosition.Y:F3}");
-        return _finite && NewSnaps == 0 && _ragdoll.Grounded && _maxEyeErr < 0.03f && _maxHandErr < 0.03f && _maxSpeed < 0.05f && _maxElbowErr < Mathf.DegToRad(8f);
+        return _finite && NewSnaps == 0 && _ragdoll.Grounded && _maxEyeErr < 0.03f && _maxHandErr < 0.03f && core < 0.03f && _maxSpeed < 0.15f && _maxElbowErr < Mathf.DegToRad(8f);
     }
 
     private readonly List<string> _reachLog = new();
@@ -435,8 +484,6 @@ public partial class RagdollSpike : Node3D
             Transform3D delta = _origin * before.AffineInverse();
             _ragdoll.TeleportBy(delta);
             _solver.Shift(delta);
-            _prevL = delta * _prevL;
-            _prevR = delta * _prevR;
             _teleported = true;
         }
         if (!_turned && _t > 0.9f)
@@ -446,8 +493,6 @@ public partial class RagdollSpike : Node3D
             _origin = rot * _origin;
             _ragdoll.TeleportBy(rot);
             _solver.Shift(rot);
-            _prevL = rot * _prevL;
-            _prevR = rot * _prevR;
             _turned = true;
         }
     }
@@ -552,6 +597,18 @@ public partial class RagdollSpike : Node3D
         _leftLocal = both ? new Transform3D(grip, new Vector3(-0.22f, y, BarHangZ + 0.03f)) : new Transform3D(Basis.Identity, new Vector3(-0.2f, 1.0f, -0.3f));
         if (!_barGrabbed && t > 0.6f && _ragdoll.Built)
         {
+            // The game's own world-grab detection must find the bar under the palm.
+            if (both)
+            {
+                for (int side = 0; side < 2; side++)
+                {
+                    RigidBody3D hand = _ragdoll.Hand(side);
+                    Vector3 palm = PropGrabber.PalmPoint(hand, side);
+                    StaticBody3D found = PropGrabber.WorldUnderPalm(palm, hand.GetWorld3D()) ?? PropGrabber.WorldUnderPalm(hand.GlobalPosition, hand.GetWorld3D());
+                    _grabDetect &= found == _bar;
+                    GD.Print($"RAGDOLL:     world grab detection side {side}: palm {palm}, bar {_bar.GlobalPosition}, found {(found == null ? "nothing" : found.Name)}");
+                }
+            }
             _barGrabbed = true;
             _barPelvisStart = _ragdoll.Pelvis.GlobalPosition.Y;
             for (int side = both ? 0 : 1; side < 2; side++)
@@ -567,6 +624,7 @@ public partial class RagdollSpike : Node3D
     }
 
     private float _twoHandRise;
+    private bool _grabDetect = true;
 
     private bool FinishPullUp(bool both)
     {
@@ -576,7 +634,8 @@ public partial class RagdollSpike : Node3D
         if (both)
         {
             _twoHandRise = _maxPelvisRise;
-            return _finite && NewSnaps == 0 && _maxPelvisRise > 0.25f;
+            GD.Print($"RAGDOLL:   world grab detection {(_grabDetect ? "found the bar" : "FAILED")}");
+            return _finite && NewSnaps == 0 && _maxPelvisRise > 0.25f && _grabDetect;
         }
         return _finite && NewSnaps == 0 && _maxPelvisRise < _twoHandRise * 0.6f;
     }
@@ -630,6 +689,42 @@ public partial class RagdollSpike : Node3D
             && _ragdoll.Eye.DistanceTo(Camera.Origin) < 0.1f && _ragdoll.Pelvis.GlobalPosition.Z > -3f;
     }
 
+    private Vector3 _crouchPelvis;
+    private float _crouchYaw, _crouchDrift, _crouchSpin;
+
+    // Squat down over 1.5 s (looking a bit down, hands in front of the knees) and hold.
+    private void TickCrouchHold(float eye)
+    {
+        float k = Mathf.SmoothStep(0f, 1f, Mathf.Min(_t / 1.5f, 1f));
+        float y = Mathf.Lerp(EyeHeight, eye, k);
+        _headLocal = new Transform3D(new Basis(Vector3.Right, -0.3f * k), new Vector3(0f, y, -0.1f * k));
+        _leftLocal = new Transform3D(Basis.Identity, new Vector3(-0.2f, Mathf.Lerp(1.0f, y - 0.6f, k), -0.35f));
+        _rightLocal = new Transform3D(Basis.Identity, new Vector3(0.2f, Mathf.Lerp(1.0f, y - 0.6f, k), -0.35f));
+        _measureFrom = float.MaxValue;
+        if (!_ragdoll.Built || _needBuild)
+            return;
+        Vector3 f = -_ragdoll.Pelvis.GlobalTransform.Basis.Z;
+        float yaw = Mathf.Atan2(-f.X, -f.Z);
+        if (_t < 2f)
+        {
+            _crouchPelvis = _ragdoll.Pelvis.GlobalPosition;
+            _crouchYaw = yaw;
+            _crouchDrift = _crouchSpin = 0f;
+            return;
+        }
+        Vector3 d = _ragdoll.Pelvis.GlobalPosition - _crouchPelvis;
+        d.Y = 0f;
+        _crouchDrift = Mathf.Max(_crouchDrift, d.Length());
+        _crouchSpin = Mathf.Max(_crouchSpin, Mathf.Abs(Mathf.AngleDifference(_crouchYaw, yaw)));
+    }
+
+    private bool FinishCrouchHold()
+    {
+        GD.Print($"RAGDOLL:   crouch hold: pelvis drift {_crouchDrift:F3} m, yaw change {Mathf.RadToDeg(_crouchSpin):F1}°, eye error {_ragdoll.Eye.DistanceTo(Camera.Origin):F3}, origin {_origin.Origin}, snaps {NewSnaps}");
+        return _finite && NewSnaps == 0 && _crouchDrift < 0.05f && _crouchSpin < Mathf.DegToRad(5f) && _origin.Origin.Length() < 0.05f
+            && _ragdoll.Eye.DistanceTo(Camera.Origin) < 0.05f;
+    }
+
     // A slope rising away (−Z) from ObstacleFront up to 1 m, then a platform.
     private void SetupRamp(float degrees)
     {