Index: firmware/App/Controllers/BalancingChamber.c
===================================================================
diff -u -r7278aeac8fdd894067a05c3bd3a177d38c0b0803 -re5c384741feb64828c1f4c32ff6daca07b20f46e
--- firmware/App/Controllers/BalancingChamber.c	(.../BalancingChamber.c)	(revision 7278aeac8fdd894067a05c3bd3a177d38c0b0803)
+++ firmware/App/Controllers/BalancingChamber.c	(.../BalancingChamber.c)	(revision e5c384741feb64828c1f4c32ff6daca07b20f46e)
@@ -34,6 +34,7 @@
 #include "TDInterface.h"
 #include "Temperature.h"
 #include "TestSupport.h"
+#include "Timers.h"
 #include "Valves.h"
 
 /**
@@ -64,6 +65,10 @@
 #define COMP_SLOPE                                  -0.000376F                                  ///< Balancing chamber temperature compensation slope factor
 #define COMP_INTERCEPT                              1.007269F                                   ///< Balancing chamber temperature compensation intercept factor
 
+#define BC_SS_VOL_DISCARD_MS                        ( 10 * SEC_PER_MIN * MS_PER_SECOND )        ///< Discard doses for 10 min before averaging.
+#define BC_SS_VOL_WINDOW_MS                         ( 2 * SEC_PER_MIN * MS_PER_SECOND )         ///< Averaging window length (2 min).
+#define BC_SS_VOL_MATCH_PCT                         0.05F                                       ///< Two consecutive window avgs must match within ±5%.
+
 /// Payload record structure for balancing chamber switch only request
 typedef struct
 {
@@ -116,6 +121,18 @@
 // Balancing chamber state change tracker
 static BAL_CHAMBER_EXEC_STATE_T prevBalChamberState;                                            ///< Balancing chamber Previous State tracking variable
 
+// Steady-state bicarb dose volume (survives initBalanceChamber / PreGen→GenD):
+// discard 10 min, then consecutive 2-min averages until two match within ±5%.
+static BOOL ssBicarbVolActive;                                                                  ///< TRUE while collecting (until SS confirmed)
+static U32  ssBicarbVolStartTimeMS;                                                             ///< Collection start time (ms) — discard gate
+static U32  ssBicarbVolWindowStartMS;                                                           ///< Current 2-min window start (ms)
+static F32  ssBicarbVolSampleSum;                                                               ///< Dose sum in current window
+static U32  ssBicarbVolSampleCount;                                                             ///< Dose count in current window
+static F32  ssBicarbVolPrevAvg;                                                                 ///< Previous 2-min window average (mL)
+static BOOL ssBicarbVolHavePrev;                                                                ///< TRUE after first completed window
+static F32  ssBicarbVolSteadyState;                                                             ///< Confirmed steady-state dose volume (mL)
+static BOOL ssBicarbVolValid;                                                                   ///< TRUE when steady-state is confirmed
+
 // ********** private function prototypes **********
 
 static BAL_CHAMBER_EXEC_STATE_T handleBalChamberState1FillStart( void );
@@ -134,6 +151,7 @@
 static BOOL isBalChamberTimeBasedSwitching( void );
 static void scheduleFirstCycleRelaxAfterQdApply( void );
 static void calculateBalancingChamberError( void );
+static void recordSteadyStateBicarbVolDoseSample( F32 bicarbVolume );
 
 /*********************************************************************//**
  * @brief
@@ -264,6 +282,156 @@
 
 /*********************************************************************//**
  * @brief
+ * The recordSteadyStateBicarbVolDoseSample function accumulates bicarb dose
+ * samples after the discard interval while SS volume is still being collected.
+ * @details \b Inputs: bicarbVolume, ssBicarbVolActive, ssBicarbVolValid,
+ * ssBicarbVolStartTimeMS
+ * @details \b Outputs: ssBicarbVolSampleSum, ssBicarbVolSampleCount
+ * @param bicarbVolume Bicarb dose volume at BC dose start (mL)
+ * @return none
+ *************************************************************************/
+static void recordSteadyStateBicarbVolDoseSample( F32 bicarbVolume )
+{
+    if ( ( TRUE == ssBicarbVolActive ) &&
+         ( FALSE == ssBicarbVolValid ) &&
+         ( TRUE == didTimeout( ssBicarbVolStartTimeMS, BC_SS_VOL_DISCARD_MS ) ) )
+    {
+        ssBicarbVolSampleSum += bicarbVolume;
+        ssBicarbVolSampleCount++;
+    }
+}
+
+/*********************************************************************//**
+ * @brief
+ * The notifySteadyStateBicarbVolCalStart function starts steady-state bicarb
+ * volume collection. Keeps an already confirmed steady-state value.
+ * @details \b Inputs: TEST_CONFIG_DD_DISABLE_DRY_BICARB, ssBicarbVolValid
+ * @details \b Outputs: ssBicarbVolActive, ssBicarbVolValid, ssBicarbVolSteadyState,
+ * ssBicarbVolPrevAvg, ssBicarbVolHavePrev, ssBicarbVolSampleSum,
+ * ssBicarbVolSampleCount, ssBicarbVolStartTimeMS, ssBicarbVolWindowStartMS
+ * @return none
+ *************************************************************************/
+void notifySteadyStateBicarbVolCalStart( void )
+{
+    if ( ( FALSE == getTestConfigStatus( TEST_CONFIG_DD_DISABLE_DRY_BICARB ) ) &&
+         ( FALSE == ssBicarbVolValid ) )
+    {
+        ssBicarbVolActive        = TRUE;
+        ssBicarbVolValid         = FALSE;
+        ssBicarbVolSteadyState   = 0.0F;
+        ssBicarbVolPrevAvg       = 0.0F;
+        ssBicarbVolHavePrev      = FALSE;
+        ssBicarbVolSampleSum     = 0.0F;
+        ssBicarbVolSampleCount   = 0;
+        ssBicarbVolStartTimeMS   = getMSTimerCount();
+        ssBicarbVolWindowStartMS = 0;
+    }
+}
+
+/*********************************************************************//**
+ * @brief
+ * The serviceSteadyStateBicarbVolCal function finishes consecutive 2-min
+ * dose averages after discard; when two consecutive averages match within
+ * ±5%, the latest average is stored as the steady-state volume.
+ * @details \b Inputs: ssBicarbVolActive, ssBicarbVolValid, ssBicarbVolStartTimeMS,
+ * ssBicarbVolWindowStartMS, ssBicarbVolSampleSum, ssBicarbVolSampleCount,
+ * ssBicarbVolHavePrev, ssBicarbVolPrevAvg
+ * @details \b Outputs: ssBicarbVolSteadyState, ssBicarbVolValid, ssBicarbVolActive,
+ * ssBicarbVolPrevAvg, ssBicarbVolHavePrev, ssBicarbVolSampleSum,
+ * ssBicarbVolSampleCount, ssBicarbVolWindowStartMS
+ * @return none
+ *************************************************************************/
+void serviceSteadyStateBicarbVolCal( void )
+{
+    F32 windowAvg = 0.0F;
+    F32 delta     = 0.0F;
+    BOOL matched  = FALSE;
+
+    if ( ( TRUE == ssBicarbVolActive ) && ( FALSE == ssBicarbVolValid ) )
+    {
+        if ( TRUE == didTimeout( ssBicarbVolStartTimeMS, BC_SS_VOL_DISCARD_MS ) )
+        {
+            // Start first averaging window when discard ends
+            if ( 0 == ssBicarbVolWindowStartMS )
+            {
+                ssBicarbVolSampleSum     = 0.0F;
+                ssBicarbVolSampleCount   = 0;
+                ssBicarbVolHavePrev      = FALSE;
+                ssBicarbVolWindowStartMS = getMSTimerCount();
+            }
+            else if ( TRUE == didTimeout( ssBicarbVolWindowStartMS, BC_SS_VOL_WINDOW_MS ) )
+            {
+                if ( ssBicarbVolSampleCount > 0 )
+                {
+                    windowAvg = ssBicarbVolSampleSum / (F32)ssBicarbVolSampleCount;
+                }
+
+                if ( ( TRUE == ssBicarbVolHavePrev ) && ( ssBicarbVolPrevAvg > 0.0F ) )
+                {
+                    delta = windowAvg - ssBicarbVolPrevAvg;
+                    if ( delta < 0.0F )
+                    {
+                        delta = -delta;
+                    }
+
+                    if ( delta <= ( ssBicarbVolPrevAvg * BC_SS_VOL_MATCH_PCT ) )
+                    {
+                        matched = TRUE;
+                    }
+                }
+
+                if ( TRUE == matched )
+                {
+                    ssBicarbVolSteadyState = windowAvg;
+                    ssBicarbVolValid       = TRUE;
+                    ssBicarbVolActive      = FALSE;
+                }
+                else
+                {
+                    // Slide window: previous = current, start next 2 min
+                    ssBicarbVolPrevAvg       = windowAvg;
+                    ssBicarbVolHavePrev      = TRUE;
+                    ssBicarbVolSampleSum     = 0.0F;
+                    ssBicarbVolSampleCount   = 0;
+                    ssBicarbVolWindowStartMS = getMSTimerCount();
+                }
+            }
+        }
+    }
+}
+
+/*********************************************************************//**
+ * @brief
+ * The isSteadyStateBicarbVolumeValid function reports whether steady-state
+ * bicarb volume has been confirmed.
+ * @details \b Inputs: ssBicarbVolValid
+ * @details \b Outputs: none
+ * @return TRUE when steady-state bicarb volume is valid
+ *************************************************************************/
+BOOL isSteadyStateBicarbVolumeValid( void )
+{
+    BOOL result = ssBicarbVolValid;
+
+    return result;
+}
+
+/*********************************************************************//**
+ * @brief
+ * The getSteadyStateBicarbVolume function returns the confirmed steady-state
+ * bicarb dose volume.
+ * @details \b Inputs: ssBicarbVolSteadyState
+ * @details \b Outputs: none
+ * @return Confirmed steady-state bicarb dose volume (mL)
+ *************************************************************************/
+F32 getSteadyStateBicarbVolume( void )
+{
+    F32 result = ssBicarbVolSteadyState;
+
+    return result;
+}
+
+/*********************************************************************//**
+ * @brief
  * The getAcidDoseVol function gets  acid mix volume
  * @details \b Inputs: acidDoseVolume
  * @details \b Outputs: none
@@ -707,6 +875,7 @@
             // start acid and bicarb pump with the expected quantity
             setConcentratePumpTargetSpeed( D11_PUMP, DOSING_CONCENTRATE_PUMP_SPEED, acidVolume );
             setConcentratePumpTargetSpeed( D10_PUMP, DOSING_CONCENTRATE_PUMP_SPEED, bicarbVolume );
+            recordSteadyStateBicarbVolDoseSample( bicarbVolume );
             requestConcentratePumpOn( D11_PUMP );
             requestConcentratePumpOn( D10_PUMP );
         }
@@ -1024,6 +1193,7 @@
             // start acid and bicarb pump with the expected quantity
             setConcentratePumpTargetSpeed( D11_PUMP, DOSING_CONCENTRATE_PUMP_SPEED, acidVolume );
             setConcentratePumpTargetSpeed( D10_PUMP, DOSING_CONCENTRATE_PUMP_SPEED, bicarbVolume );
+            recordSteadyStateBicarbVolDoseSample( bicarbVolume );
             requestConcentratePumpOn( D11_PUMP );
             requestConcentratePumpOn( D10_PUMP );
         }