Jumpbug: automatic duck+jump on damaging falls

- Predict the landing speed from the current vertical velocity and a swept
  standing-hull ground trace; engage only when it exceeds
  PLAYER_MAX_SAFE_FALL_SPEED.
- Press duck one command before the unduck window so FinishDuck's 36-unit
  origin raise places the feet ~37 units above the floor.
- On the next command release duck and press jump: PlayerMove runs Duck()
  before CheckJumpButton, so FinishUnDuck sets ground, the jump executes, and
  CheckFalling never sees ground for the fall-damage check.
- Measure the per-command fall from consecutive airborne origins instead of a
  fixed tick interval; clear IN_JUMP while waiting so the pogo latch is clear.
- New Movement -> Jumpbug -> Active toggle (default on), config [jumpbug].

4 files changed, 252 insertions, 15 deletions

diff --git a/src/hl2h.cpp b/src/hl2h.cpp
index 4947b18..125d94e 100644
--- a/src/hl2h.cpp
+++ b/src/hl2h.cpp
@@ -166,7 +166,184 @@ static void apply_autostrafe(CUserCmd *cmd, const float *vel) {
   cmd->sidemove = (dx * rx + dy * ry) * 450.0f;
 }
 
-static void do_move(int seq) {
+// ---------------------------------------------------------------------------
+// jumpbug
+// ---------------------------------------------------------------------------
+//
+// Source jumpbug: while falling, hold duck; on the frame where unducking would
+// leave the standing hull within CategorizePosition's 2-unit ground probe,
+// release duck and press jump. PlayerMove calls Duck() before FullWalkMove's
+// CheckJumpButton, so FinishUnDuck -> CategorizePosition sets the ground
+// entity, the jump executes in the same frame, and CheckFalling never sees
+// ground for the fall-damage test.
+//
+// In air, FinishDuck raises the feet by 36 units (the standing hull is 72
+// tall, the duck hull 36). We exploit that as a one-frame phase shift: press
+// duck when the standing distance x to the floor is about `drop` units, so
+// after this frame's fall the ducked feet sit ~37 units above the floor (the
+// middle of the [36, 38] unduck window) and the next frame can jump.
+
+static constexpr float JB_SAFE_FALL = 526.5f;
+static constexpr float JB_GRAVITY = 600.0f;
+static constexpr float JB_DUCK_RAISE = 36.0f;
+
+static int jb_state = 0; // 0 idle, 1 ducked/waiting for the unduck window
+static int jb_local = -1;
+static float jb_prev_z = 0.0f;
+static bool jb_prev_valid = false;
+static bool jb_prev_ducked = false;
+static float jb_drop = 0.0f; // last measured vertical fall per command
+static int jb_logs = 0;
+static bool jb_tracked = false;
+
+static bool game_running() {
+  if (!g_iface.engine)
+    return true;
+  using BoolFn = bool (*)(void *);
+  if (!vfunc<BoolFn>(g_iface.engine, 26)(g_iface.engine))
+    return false;
+  if (vfunc<BoolFn>(g_iface.engine, 84)(g_iface.engine))
+    return false;
+  return true;
+}
+
+static void jumpbug_reset() {
+  jb_state = 0;
+  jb_prev_valid = false;
+  jb_tracked = false;
+}
+
+static bool jumpbug_apply(CUserCmd *cmd, int local, void *ent, int flags,
+                          const float *vel, float frametime) {
+  if (!feature_active(FEAT_JUMPBUG) || !g_iface.engine ||
+      g_net.origin < 0 || g_net.velocity < 0) {
+    jumpbug_reset();
+    return false;
+  }
+  if (!game_running()) {
+    jumpbug_reset();
+    return false;
+  }
+
+  bool onground = (flags & FL_ONGROUND) != 0;
+  bool inwater = (flags & FL_INWATER) != 0;
+  bool ducked = (flags & FL_DUCKING) != 0;
+  uintptr_t e = (uintptr_t)ent;
+  int movetype =
+      g_net.movetype >= 0 ? *(int *)(e + g_net.movetype) : MOVETYPE_WALK;
+
+  if (onground || inwater || movetype != MOVETYPE_WALK ||
+      (g_net.health >= 0 && *(int *)(e + g_net.health) <= 0)) {
+    jumpbug_reset();
+    return false;
+  }
+
+  Vector origin{*(float *)(e + g_net.origin),
+                *(float *)(e + g_net.origin + 4),
+                *(float *)(e + g_net.origin + 8)};
+  float vz = vel[2];
+
+  if (local != jb_local) {
+    jb_local = local;
+    jumpbug_reset();
+    jb_drop = 0.0f;
+    jb_logs = 0;
+  }
+
+  // Measure the previous command's fall. Both endpoints must be airborne and
+  // standing: a duck transition moves the origin by 36 units and would
+  // otherwise look like a huge fall.
+  if (jb_prev_valid && !jb_prev_ducked && !ducked) {
+    float d = jb_prev_z - origin.z;
+    if (d > 0.05f && d < 250.0f)
+      jb_drop = d;
+  }
+  jb_prev_valid = true;
+  jb_prev_z = origin.z;
+  jb_prev_ducked = ducked;
+
+  if (vz > -10.0f) { // not falling
+    jb_state = 0;
+    jb_tracked = false;
+    return false;
+  }
+
+  float x = ground_distance(origin, ent, 2048.0f);
+  if (x < 0.0f) { // no standable surface below
+    jb_state = 0;
+    jb_tracked = false;
+    return false;
+  }
+  float impact = sqrtf(vz * vz + 2.0f * JB_GRAVITY * x);
+  if (impact <= JB_SAFE_FALL + 0.5f) {
+    jb_tracked = false;
+    jb_state = 0;
+    return false;
+  }
+  if (!jb_tracked) {
+    jb_tracked = true;
+    logf("jumpbug: tracking x=%.1f vz=%.1f impact=%.1f", x, vz, impact);
+  }
+
+  if (jb_drop <= 0.05f) {
+    // No measured fall yet. Bias toward the default 15 ms Source tick when
+    // the input frametime is smaller: setting the duck up early leaves us
+    // ducked above the window, where we can wait; setting it up late would
+    // put us below the unduck window and lose the jump.
+    float dt = frametime;
+    if (!(dt > 0.0f && dt < 0.05f) || dt < 0.015f)
+      dt = 0.015f;
+    jb_drop = -vz * dt + 0.5f * JB_GRAVITY * dt * dt;
+    if (jb_drop < 0.05f)
+      jb_drop = 0.05f;
+  }
+
+  int before = cmd->buttons;
+  bool trigger = false;
+
+  if (ducked) {
+    if (x >= JB_DUCK_RAISE && x <= JB_DUCK_RAISE + 2.0f) {
+      // In the window: unduck (CategorizePosition sets ground) and jump in
+      // the same command.
+      cmd->buttons &= ~IN_DUCK;
+      cmd->buttons |= IN_JUMP;
+      trigger = true;
+      jb_state = 0;
+      jb_tracked = false;
+      if (jb_logs < 20) {
+        jb_logs++;
+        logf("jumpbug: trigger x=%.2f drop=%.2f vz=%.1f", x, jb_drop, vz);
+      }
+    } else {
+      // Hold the crouch and wait for the window. Staying ducked is required
+      // for the unduck trick; releasing early would just add a phase shift
+      // and fight a user who is holding crouch.
+      cmd->buttons |= IN_DUCK;
+      jb_state = 1;
+    }
+  } else {
+    if (jb_state == 1)
+      jb_state = 0; // expected to be ducked but is not
+    if (x <= jb_drop + 2.0f) {
+      // Setup frame: raise the feet 36 units here so the next frame starts
+      // near the middle of the unduck window.
+      cmd->buttons |= IN_DUCK;
+      jb_state = 1;
+      if (jb_logs < 20) {
+        jb_logs++;
+        logf("jumpbug: setup x=%.2f drop=%.2f pred=%.2f vz=%.1f", x, jb_drop,
+             x + JB_DUCK_RAISE - jb_drop, vz);
+      }
+    }
+  }
+
+  if (!trigger && (cmd->buttons & IN_JUMP))
+    cmd->buttons &= ~IN_JUMP; // keep the pogo latch clear for the trigger
+
+  return cmd->buttons != before;
+}
+
+static void do_move(int seq, float frametime) {
   static bool g_echo_sent = false;
   if (!g_input || !g_net.ok())
     return;
@@ -206,6 +383,7 @@ static void do_move(int seq) {
   int flags = *(int *)(e + g_net.flags);
   bool onground = (flags & FL_ONGROUND) != 0;
   bool inwater = (flags & FL_INWATER) != 0;
+  const float *vel = (const float *)(e + g_net.velocity);
 
   bool bhop_on = feature_active(FEAT_BHOP);
   bool abh_on = feature_active(FEAT_ABH);
@@ -217,7 +395,6 @@ static void do_move(int seq) {
       lastground = onground;
       return;
     }
-    const float *vel = (const float *)(e + g_net.velocity);
     float speed = sqrtf(vel[0] * vel[0] + vel[1] * vel[1] + vel[2] * vel[2]);
     bool moving = speed > 0.1f;
     bool backmove = false;
@@ -260,6 +437,9 @@ static void do_move(int seq) {
     }
   }
 
+  if (jumpbug_apply(cmd, localIdx, ent, flags, vel, frametime))
+    note_modified(cmd, flags, vel);
+
   if (!feature_active(FEAT_AIMBOT) || !feature_has_bind(FEAT_AIMBOT))
     aimbot_reset_lock();
   if (!feature_active(FEAT_SILENTAIM) || !feature_has_bind(FEAT_SILENTAIM))
@@ -361,7 +541,7 @@ static void hkdPaintTraverseEx(void *self, long panel, bool paintPopups) {
 
 static bool hkdCreateMove(void *self, int seq, float frametime, bool active) {
   bool ret = oCreateMove(self, seq, frametime, active);
-  do_move(seq);
+  do_move(seq, frametime);
 
   // Hook ISurface once: PaintTraverseEx (slot 114) fires every frame; keep
   // DrawPrintText (slot 22) hooked as a fallback text-draw trigger.
diff --git a/src/hl2h.h b/src/hl2h.h
index fdc88c1..92ae3f1 100644
--- a/src/hl2h.h
+++ b/src/hl2h.h
@@ -128,8 +128,8 @@ struct CUserCmd {
 // ---------------------------------------------------------------------------
 
 enum { IN_ATTACK = 1 << 0, IN_JUMP = 1 << 1, IN_DUCK = 1 << 2, IN_USE = 1 << 5 };
-enum { FL_ONGROUND = 1 << 0, FL_INWATER = 1 << 9 };
-enum { MOVETYPE_NOCLIP = 8, MOVETYPE_LADDER = 9 };
+enum { FL_ONGROUND = 1 << 0, FL_DUCKING = 1 << 1, FL_INWATER = 1 << 9 };
+enum { MOVETYPE_WALK = 2, MOVETYPE_NOCLIP = 8, MOVETYPE_LADDER = 9 };
 
 // ---------------------------------------------------------------------------
 // vector math
@@ -152,7 +152,8 @@ enum FeatureId {
   FEAT_ESP = 2,
   FEAT_AIMBOT = 3,
   FEAT_TRIGGERBOT = 4,
-  FEAT_SILENTAIM = 5
+  FEAT_SILENTAIM = 5,
+  FEAT_JUMPBUG = 6
 };
 enum EspOption {
   ESP_OPT_SHOW_NEUTRAL = 0,
@@ -200,6 +201,7 @@ bool world_to_screen(const Vector &w, float &sx, float &sy);
 void set_silent_restore(const QAngle &angles);
 bool is_visible(const Vector &eye, const Vector &point);
 void *trace_entity(const Vector &start, const Vector &end, void *ignore);
+float ground_distance(const Vector &origin, void *ignore, float max_dist);
 
 // bones.cpp — client-side animated skeleton / hitbox access (see there)
 bool bones_update(int idx, void *ent);
diff --git a/src/menu.cpp b/src/menu.cpp
index 3e20cb3..0ed89d4 100644
--- a/src/menu.cpp
+++ b/src/menu.cpp
@@ -62,6 +62,7 @@ static FeatureState g_bhop{true, 0};
 static bool g_bhop_autostrafe = true;
 
 static FeatureState g_abh{true, 0};
+static FeatureState g_jumpbug{true, 0};
 static FeatureState g_esp{true, 0};
 static FeatureState g_aimbot{true, 604}; // default Mouse5, rebindable in menu
 static FeatureState g_triggerbot{true, 603}; // default Mouse4
@@ -96,6 +97,8 @@ static MenuNode g_bhop_active{NODE_TOGGLE, "Active", false, 0, {}, &g_bhop.activ
 static MenuNode g_bhop_autostrafe_node{NODE_TOGGLE, "Uni-directional auto-strafe", false, 0, {}, &g_bhop_autostrafe, nullptr, nullptr};
 static MenuNode g_abh_feat{NODE_FEATURE, "ABH", false, 1, {}, nullptr, nullptr, nullptr};
 static MenuNode g_abh_active{NODE_TOGGLE, "Active", false, 0, {}, &g_abh.active, nullptr, nullptr};
+static MenuNode g_jumpbug_feat{NODE_FEATURE, "Jumpbug", false, 1, {}, nullptr, nullptr, nullptr};
+static MenuNode g_jumpbug_active{NODE_TOGGLE, "Active", false, 0, {}, &g_jumpbug.active, nullptr, nullptr};
 static MenuNode g_esp_feat{NODE_FEATURE, "ESP", false, 1, {}, nullptr, nullptr, nullptr};
 static MenuNode g_esp_active{NODE_TOGGLE, "Active", false, 0, {}, &g_esp.active, nullptr, nullptr};
 static MenuNode g_esp_opt_nodes[ESP_OPT_COUNT] = {
@@ -145,6 +148,9 @@ static void build_tree() {
   g_bhop_feat.children[1] = &g_bhop_autostrafe_node;
   g_bhop_feat.child_count = 2;
   g_abh_feat.children[0] = &g_abh_active;
+  g_abh_feat.child_count = 1;
+  g_jumpbug_feat.children[0] = &g_jumpbug_active;
+  g_jumpbug_feat.child_count = 1;
   g_esp_feat.children[0] = &g_esp_active;
   g_aimbot_feat.children[0] = &g_aimbot_active;
   g_aimbot_feat.children[1] = &g_aimbot_bind;
@@ -169,11 +175,12 @@ static void build_tree() {
   g_esp_feat.child_count = ESP_OPT_COUNT + 1;
   g_root.children[0] = &g_bhop_feat;
   g_root.children[1] = &g_abh_feat;
-  g_root.children[2] = &g_esp_feat;
-  g_root.children[3] = &g_aimbot_feat;
-  g_root.children[4] = &g_triggerbot_feat;
-  g_root.children[5] = &g_silentaim_feat;
-  g_root.child_count = 6;
+  g_root.children[2] = &g_jumpbug_feat;
+  g_root.children[3] = &g_esp_feat;
+  g_root.children[4] = &g_aimbot_feat;
+  g_root.children[5] = &g_triggerbot_feat;
+  g_root.children[6] = &g_silentaim_feat;
+  g_root.child_count = 7;
 }
 
 static int g_depth[48]; // depth of each visible row (for indentation)
@@ -295,6 +302,7 @@ static void config_save() {
   fprintf(f, "[bhop]\nactive=%d\nbind=%d\nautostrafe=%d\n", g_bhop.active,
           g_bhop.bind, g_bhop_autostrafe);
   fprintf(f, "[abh]\nactive=%d\nbind=%d\n", g_abh.active, g_abh.bind);
+  fprintf(f, "[jumpbug]\nactive=%d\n", g_jumpbug.active);
   fprintf(f, "[aimbot]\nactive=%d\nbind=%d\nsmooth=%d\nvischeck=%d\n"
              "fov=%d\nfov_circle=%d\n"
              "bone_head=%d\nbone_torso=%d\nbone_larm=%d\nbone_rarm=%d\n"
@@ -332,6 +340,8 @@ static void config_load() {
         cur = &g_bhop;
       else if (strstr(line, "[abh]"))
         cur = &g_abh;
+      else if (strstr(line, "[jumpbug]"))
+        cur = &g_jumpbug;
       else if (strstr(line, "[esp]"))
         cur = &g_esp;
       else if (strstr(line, "[aimbot]"))
@@ -516,10 +526,10 @@ static bool key_pressed(int sc) {
 // feature gate queried from hl2h.cpp do_move(): feature must be Active AND
 // its bind key held (always-on when unbound).
 static FeatureState *feature_state(int feature) {
-  static FeatureState *feats[6] = {&g_bhop,    &g_abh,     &g_esp,
-                                   &g_aimbot,  &g_triggerbot,
-                                   &g_silentaim};
-  if (feature < 0 || feature > 5)
+  static FeatureState *feats[7] = {&g_bhop,   &g_abh,        &g_esp,
+                                   &g_aimbot, &g_triggerbot, &g_silentaim,
+                                   &g_jumpbug};
+  if (feature < 0 || feature > 6)
     return nullptr;
   return feats[feature];
 }
diff --git a/src/vischeck.cpp b/src/vischeck.cpp
index 428f54f..6d453c5 100644
--- a/src/vischeck.cpp
+++ b/src/vischeck.cpp
@@ -95,6 +95,9 @@ constexpr unsigned MASK_VISIBLE = 0x1u | 0x4000u | 0x80u | 0x2000u;
 // MASK_SHOT = SOLID|MOVEABLE|MONSTER|WINDOW|DEBRIS|HITBOX
 constexpr unsigned MASK_SHOT = 0x1u | 0x4000u | 0x2000000u | 0x4u |
                                0x4000000u | 0x40000000u;
+// MASK_PLAYERSOLID = SOLID|MOVEABLE|PLAYERCLIP|WINDOW|MONSTER|GRATE
+constexpr unsigned MASK_PLAYERSOLID =
+    0x1u | 0x4000u | 0x10000u | 0x4u | 0x2000000u | 0x8u;
 
 static void make_ray(RayCompat &ray, const Vector &start, const Vector &end) {
   float dx = end.x - start.x, dy = end.y - start.y, dz = end.z - start.z;
@@ -107,6 +110,21 @@ static void make_ray(RayCompat &ray, const Vector &start, const Vector &end) {
   ray.isSwept = (dx * dx + dy * dy + dz * dz) > 0.0f;
 }
 
+// Swept AABB matching the standing player hull used by CGameMovement.
+// Ray_t::Init shifts m_Start to the box center and stores the negated center
+// offset in m_StartOffset. With mins=(-16,-16,0), maxs=(16,16,72), the
+// extents are (16,16,36) and m_StartOffset is (0,0,-36).
+static void make_standing_hull_ray(RayCompat &ray, const Vector &origin,
+                                   float distance) {
+  ray = RayCompat{};
+  ray.start = {origin.x, origin.y, origin.z + 36.0f, 0.0f};
+  ray.delta = {0.0f, 0.0f, -distance, 0.0f};
+  ray.startOffset = {0.0f, 0.0f, -36.0f, 0.0f};
+  ray.extents = {16.0f, 16.0f, 36.0f, 0.0f};
+  ray.isRay = false;
+  ray.isSwept = true;
+}
+
 } // namespace
 
 bool is_visible(const Vector &eye, const Vector &point) {
@@ -147,3 +165,30 @@ void *trace_entity(const Vector &start, const Vector &end, void *ignore) {
     return nullptr;
   return tr.ent;
 }
+
+// Vertical distance from the standing player hull's feet to the first
+// standable surface below. Matches CategorizePosition's 2-unit probe and its
+// plane.normal.z >= 0.7 rule, but sweeps much farther so the caller can
+// predict the landing. Returns -1 when there is no usable ground.
+float ground_distance(const Vector &origin, void *ignore, float max_dist) {
+  if (!g_iface.enginetrace || max_dist <= 0.0f)
+    return -1.0f;
+  RayCompat ray;
+  make_standing_hull_ray(ray, origin, max_dist);
+  GameTraceCompat tr{};
+  EntityFilter filter(ignore);
+  using TraceRayFn = void (*)(void *, const RayCompat *, unsigned, void *,
+                              GameTraceCompat *);
+  vfunc<TraceRayFn>(g_iface.enginetrace, 4)(g_iface.enginetrace, &ray,
+                                            MASK_PLAYERSOLID, &filter, &tr);
+  if (tr.startsolid || tr.fraction >= 1.0f || tr.normal.z < 0.7f) {
+    static int solid_logs = 0;
+    if (tr.startsolid && solid_logs < 4) {
+      solid_logs++;
+      logf("ground trace: startsolid at (%.1f %.1f %.1f)", origin.x,
+           origin.y, origin.z);
+    }
+    return -1.0f;
+  }
+  return tr.fraction * max_dist;
+}