Correct handplant collision bone indices to prevent arm drive collapse

crates/skate-core/src/physics/skeleton_body/collision_mode.rs

@@ -39,6 +39,17 @@ pub struct SkeletonCollisionMode {
 }
 
 impl SkeletonCollisionMode {
+    ///82D91298: Body volume pointers start at3092, counters at8128.
+    /// The stores at3120/3104/3124/3108/3096 therefore select parts7/3/8/4/1:
+    /// both hands, both forearms and the head, not the next bone in each chain.
+    pub fn disable_handplant_contacts(&mut self, frames: u32) {
+        self.pending_reenable = true;
+        for part in [7, 3, 8, 4, 1] {
+            self.disable_count[part] = frames;
+            self.parts[part].enabled = false;
+        }
+    }
+
     ///82BE7078, used by the real teleport path82BE3508. Collision volume
     ///enabled flags and materials survive this reset.
     pub fn reset_body_state(&mut self, feedback: &mut SkeletonCollisionFeedback) {

crates/skate-core/src/physics/skeleton_body/tests/collision_feedback.rs

@@ -1,6 +1,33 @@
 use super::*;
 use crate::physics::{contact::RetailContactMaterial, skeleton_animation_record::IDENTITY};
 
+#[test]
+fn handplant_contact_mask_survives_updates_and_restores_on_exit() {
+    let mut collision = SkeletonCollisionMode::new_normal(settings().body, false);
+    for _ in 0..3 {
+        collision.disable_handplant_contacts(2);
+        // A driven-state refresh must not restore these volumes mid-plant.
+        collision.select_driven(5).unwrap();
+        for part in [1, 3, 4, 7, 8] {
+            assert!(!collision.parts[part].enabled, "plant contact part {part}");
+        }
+        for part in [2, 5, 6, 9, 10, 15, 19] {
+            assert!(collision.parts[part].enabled, "unaffected part {part}");
+        }
+        collision.finish_contact_frame();
+        assert!(collision.pending_reenable);
+        assert_eq!(collision.disable_count[3], 1);
+        assert!(!collision.parts[3].enabled);
+    }
+    // No refresh from the plant on the next tick: restore normal contact.
+    collision.finish_contact_frame();
+    assert!(!collision.pending_reenable);
+    for part in [1, 3, 4, 7, 8] {
+        assert!(collision.parts[part].enabled);
+        assert_eq!(collision.disable_count[part], 0);
+    }
+}
+
 fn settings() -> SkeletonFeedbackSettings {
     SkeletonFeedbackSettings {
         body: SkeletonCollisionSettings {

crates/skate-game/src/physics/handplant.rs

@@ -269,12 +269,8 @@ pub(super) fn enter(physics: &mut GamePhysics, skater: &mut SkaterRuntime) -> Re
     Ok(())
 }
 pub(super) fn update(physics: &mut GamePhysics, skater: &mut SkaterRuntime) -> Result<(), String> {
-    //82D4C3D8 ->82D91298 disables five upper-body volumes for two frames.
-    for part in [8, 4, 9, 5, 2] {
-        skater.skeleton_collision.pending_reenable = true;
-        skater.skeleton_collision.disable_count[part] = 2;
-        skater.skeleton_collision.parts[part].enabled = false;
-    }
+    //82D4C3D8 ->82D91298: keep planted hands out of collision response.
+    skater.skeleton_collision.disable_handplant_contacts(2);
     let h = &mut skater.handplant;
     h.warped += (1.0 + h.settings.time_warp.evaluate(h.warped - h.apex)) * STEP;
     h.estimate_apex();

docs/plants.md

@@ -230,3 +230,30 @@ the selected arm, two0.65m clamps and feet-only external post pass match the
 existing port. Need another normal/A/B reproduction to locate the divergence.
 The same run later terminates in unsupported IsGrindBluntingBackslash at8059;
 that separate grind condition remains unresolved by this diagnostic change.
+
+## Handplant collision-mask correction (8 September, 18:06 run)
+
+The requested normal/A/B reproduction is plants-20260908-180656-119-4993.log.
+Normal plant316..395 returns to Ground; variations767..788 and1139..1166
+request pose-displacement bail1. Solved traces show the free hand tracking
+within0.006m at324, then falling0.57m behind at340. Its IK adjustment is
+only0.002m at340. Collision weight drops to0 and the arm switches to soft
+drives with local/root strengths0.5/0.0. Both variation attempts repeat this
+sequence. No crash was recorded in this run.
+
+Confirmed source error:82D91298's five volume-pointer writes use offsets
+3120,3104,3124,3108,3096; matching counter writes are8156,8140,8160,8144,8132.
+The generic EnableBone82BE7190 independently establishes the volume base as
+4*773=3092 and counter base as4*2032=8128. Both address sets therefore resolve
+to parts7,3,8,4,1 (hands, forearms, head). The port incorrectly disabled
+8,4,9,5,2, leaving the hands and head collidable. TU3 dump identity remains
+SHA256 f4aa113eb541bfba03dbc108cf5ab43f58c965b20fa3b82f9c40938a0ad841c4.
+Evidence: logs/recomp-82d91298.asm and logs/recomp-82be7190.asm.
+
+Handplant now calls a shared collision-owner method with the corrected
+five-part mask and native two-frame countdown. A regression test checks
+refresh during the plant, survival across normal driven-state setup, other
+bones retaining contact, and automatic re-enabling after exit. Bail
+thresholds and authored animation/IK targets are unchanged. The native mask
+error is fixed; visual recovery and successful variations need gameplay
+confirmation from the user. The game has not been launched by the agent.