diff --git a/game/reconstructed/mech.cpp b/game/reconstructed/mech.cpp
index 3b664f8..d7456c2 100644
--- a/game/reconstructed/mech.cpp
+++ b/game/reconstructed/mech.cpp
@@ -1872,6 +1872,12 @@ void
 	case 3:		// leg/body state + stability
 		{
 			Mech__StateUpdateRecord *record = (Mech__StateUpdateRecord *)message;
+			if (getenv("BT_GAITEV"))
+				DEBUG_STREAM << "[t3rx] legState=" << record->legState
+					<< " reset=" << record->legResetLatch
+					<< " myLegState=" << (int)legStateAlarm.GetLevel()
+					<< " myLegFrm=" << legAnimation.currentFrame
+					<< " spd=" << record->speedDemand << "\n" << std::flush;
 			{
 				// CLOCK GUARD (keyboard-skip fix): the base reader stamps lastUpdate=Now()
 				// on EVERY record ('HACK' per SIMULATE.cpp:276).  Non-pose records carry no
diff --git a/game/reconstructed/mech4.cpp b/game/reconstructed/mech4.cpp
index ff1a406..08b8e71 100644
--- a/game/reconstructed/mech4.cpp
+++ b/game/reconstructed/mech4.cpp
@@ -2124,6 +2124,41 @@ void
 					legCycleSpeed = 0.0f;
 				(void)AdvanceLegAnimation(dt);		// joints only; travel = DeadReckon
 
+				// GAIT-EVENNESS probe (BT_GAITEV, 1s stats): the metric of the VISIBLE
+				// speed-change glitch -- per-frame leg-clip advance regularity + leg-state
+				// transition (flap) rate on the peer.  Position dead-reckons smoothly
+				// regardless; the churn shows in the LEGS.
+				if (getenv("BT_GAITEV"))
+				{
+					static float s_gvPrevF = -1.0f, s_gvAcc = 0.0f, s_gvSum = 0.0f, s_gvMax = 0.0f;
+					static int   s_gvN = 0, s_gvBack = 0, s_gvTrans = 0, s_gvPrevSt = -1;
+					static float s_gvDemPrev = 0.0f; static int s_gvDemChg = 0;
+					const float gf = (float)legAnimation.currentFrame;
+					const int   gs = (int)legStateAlarm.GetLevel();
+					if (s_gvPrevF >= 0.0f)
+					{
+						float df = gf - s_gvPrevF;
+						if (df < -5.0f) df += 20.0f;			// clip wrap heal (approx)
+						const float adf = (df < 0.0f) ? -df : df;
+						s_gvSum += adf; if (adf > s_gvMax) s_gvMax = adf;
+						if (df < 0.0f) s_gvBack++;
+						s_gvN++;
+					}
+					if (s_gvPrevSt >= 0 && gs != s_gvPrevSt) s_gvTrans++;
+					if ((float)bodyTargetSpeed != s_gvDemPrev) { s_gvDemChg++; s_gvDemPrev = (float)bodyTargetSpeed; }
+					s_gvPrevF = gf; s_gvPrevSt = gs; s_gvAcc += dt;
+					if (s_gvAcc >= 1.0f && s_gvN > 0)
+					{
+						DEBUG_STREAM << "[gaitev] frmAvg=" << (s_gvSum / s_gvN)
+							<< " frmMax=" << s_gvMax
+							<< " back=" << s_gvBack << "/" << s_gvN
+							<< " stateFlips/s=" << s_gvTrans
+							<< " demChanges/s=" << s_gvDemChg
+							<< " state=" << gs << "\n" << std::flush;
+						s_gvAcc = 0.0f; s_gvSum = 0.0f; s_gvMax = 0.0f; s_gvN = 0; s_gvBack = 0; s_gvTrans = 0; s_gvDemChg = 0;
+					}
+				}
+
 				// TURN-STEP rate probe (BT_TRNRATE, 0.5s): body rotation rate vs trn clip advance.
 				if (getenv("BT_TRNRATE"))
 				{
@@ -2522,6 +2557,35 @@ void
 								: (r < 1.0f ? sAutoDrive * r : sAutoDrive);
 						}
 					}
+					// BT_DRIVE_SWEEP=<period>: triangle-sweep the FORCED throttle
+					// 0.2..0.9 -- sweeps the ACTUAL drive velocity AND (via mechmppr's
+					// forced key_throttle) the mapper demand together, the true
+					// keyboard accel/decel regime.  BT_FORCE_STEP=1 quantizes it to
+					// the RIO Ranger 0.05 grid (the authentic stepped input shape).
+					{
+						static float s_dsP = -1.0f, s_dsClock = 0.0f;
+						static int   s_dsStep = -1;
+						if (s_dsP < 0.0f)
+						{
+							const char *v = getenv("BT_DRIVE_SWEEP");
+							s_dsP = v ? (float)atof(v) : 0.0f;
+							s_dsStep = getenv("BT_FORCE_STEP") ? 1 : 0;
+						}
+						if (s_dsP > 0.0f)
+						{
+							s_dsClock += dt;
+							float ph  = fmodf(s_dsClock, 2.0f * s_dsP) / s_dsP;
+							float tri = (ph < 1.0f) ? ph : (2.0f - ph);
+							// BT_DRIVE_SWEEP0=1: sweep 0.0..0.7 (through STOP each cycle -- the
+							// stand<->walk gauntlet: walk-entry, came-to-rest sends, type-3 stomps).
+							static int s_dsZero = -1;
+							if (s_dsZero < 0) s_dsZero = getenv("BT_DRIVE_SWEEP0") ? 1 : 0;
+							float thr = s_dsZero ? (0.7f * tri) : (0.2f + 0.7f * tri);
+							if (s_dsStep)
+								thr = floorf(thr / 0.05f + 0.5f) * 0.05f;
+							gBTDrive.forcedThrottle = thr;
+						}
+					}
 				}
 				else if (sGotoDrive)
 				{
@@ -2580,8 +2644,37 @@ void
 				else                     sStick  = 0.0f;
 			}
 
-			gBTDrive.throttle = sLever;
-			gBTDrive.turn     = sStick;
+			// RIO-GRID PUBLISH (authentic input shaping; decomp workflow w0odszxro):
+			// the pod's analog lever/stick reached the mapper through the RIO Ranger
+			// (800 ADC counts, 0.05 deadband -- L4RIO.cpp:801), so the DEMAND the 1995
+			// machinery consumed moved in coarse, settled STEPS with silence between
+			// them -- one type-2 speed record per step, and each gait threshold
+			// (standSpeed etc., zero hysteresis) crossed ONCE per maneuver.  Our
+			// keyboard integrator sweeps CONTINUOUSLY (kLeverRate every frame of a
+			// key-hold): ~86 records per accel, demand DWELLING on the knife edges ->
+			// transition-clip churn -- the speed-change peer glitch.  Publish on the
+			// Ranger's own 0.05 grid: internal lever feel unchanged, published demand
+			// steps like the real hardware (a bucket holds ~4 frames at kLeverRate, so
+			// the send gate self-closes between steps).  Also kills -epsilon reverse
+			// publishes from rest (bucket rounds to 0 until the lever passes -0.025;
+			// authentic reverse is a BUTTON sign-flip, never a sweep through zero).
+			// DEFAULT: CONTINUOUS publish (authentic -- the pod lever was analog,
+			// 800-count ADC ~= continuous; empirical A/B found NO gait/position
+			// difference between swept and stepped demand after the clock-guard +
+			// heading-integrator fixes, so the grid gains nothing and makes the
+			// DRIVE step unauthentically).  BT_GRID_LEVER=1 keeps the 0.05-grid
+			// variant for experiments.
+			static const int s_gridLever = getenv("BT_GRID_LEVER") ? 1 : 0;
+			if (s_gridLever)
+			{
+				gBTDrive.throttle = floorf(sLever / 0.05f + 0.5f) * 0.05f;
+				gBTDrive.turn     = floorf(sStick / 0.05f + 0.5f) * 0.05f;
+			}
+			else
+			{
+				gBTDrive.throttle = sLever;
+				gBTDrive.turn     = sStick;
+			}
 		}
 
 		// DEATH GATE (task #52): a DESTROYED mech takes no pilot input -- kill
diff --git a/game/reconstructed/mechmppr.cpp b/game/reconstructed/mechmppr.cpp
index 91199c1..6b946a2 100644
--- a/game/reconstructed/mechmppr.cpp
+++ b/game/reconstructed/mechmppr.cpp
@@ -665,6 +665,13 @@ void
 						float ph  = fmodf(s_swpClock, 2.0f * s_swpP) / s_swpP;	// 0..2
 						float tri = (ph < 1.0f) ? ph : (2.0f - ph);				// 0..1..0
 						key_throttle = 0.2f + 0.7f * tri;
+						// BT_FORCE_STEP=1: quantize the swept throttle to the RIO
+						// Ranger 0.05 grid (the authentic ADC/deadband step) -- the
+						// stepped-vs-continuous A/B for the speed-change glitch.
+						static int s_swpStep = -1;
+						if (s_swpStep < 0) s_swpStep = getenv("BT_FORCE_STEP") ? 1 : 0;
+						if (s_swpStep)
+							key_throttle = floorf(key_throttle / 0.05f + 0.5f) * 0.05f;
 					}
 				}
 				// BT_FORCE_FLIP=<t>: invert the forced throttle after t sim-seconds