Index: firmware/App/Modes/ModePreTreat.c
===================================================================
diff -u -rbe1f6ba8f58abfe098865c85ebca070eb0dde6ce -r6f02ff4686ec9dfc60247e9ed3fc9c5cc7771543
--- firmware/App/Modes/ModePreTreat.c	(.../ModePreTreat.c)	(revision be1f6ba8f58abfe098865c85ebca070eb0dde6ce)
+++ firmware/App/Modes/ModePreTreat.c	(.../ModePreTreat.c)	(revision 6f02ff4686ec9dfc60247e9ed3fc9c5cc7771543)
@@ -1,7 +1,25 @@
+/**************************************************************************
+*
+* Copyright (c) 2025-2026 Diality Inc. - All Rights Reserved.
+*
+* THIS CODE MAY NOT BE COPIED OR REPRODUCED IN ANY FORM, IN PART OR IN
+* WHOLE, WITHOUT THE EXPLICIT PERMISSION OF THE COPYRIGHT OWNER.
+*
+* @file    ModePreTreat.c
+*
+* @author  (last)      Varshini Nagabooshanam
+* @date    (last)      26-Jan-2026
+*
+* @author  (original)  Dara Navaei
+* @date    (original)  25-Sep-2025
+*
+***************************************************************************/
 
+#include "Buttons.h"
 #include "ModePreTreat.h"
 #include "OperationModes.h"
 #include "Timers.h"
+#include "TxParams.h"
 
 /**
  *  @addtogroup TDPreTreatmentMode
@@ -12,58 +30,132 @@
 
 // ********** private data **********
 
-static U32 testTimeRemove = 0;
+static TD_PRE_TREATMENT_MODE_STATE_T currentPreTreatmentState;              ///< Current Pre-Treatment sub-state
 
 // ********** private function prototypes **********
 
+static TD_PRE_TREATMENT_MODE_STATE_T handleRxState( void );                 ///< Handle Confirm Rx state during Pre-Treatment
+
 /*********************************************************************//**
- * @brief
- * The initPreTreatmentMode function initializes the Pre Treatment Mode unit.
- * @details \b Inputs: none
- * @details \b Outputs: Pre Treatment Mode unit initialized.
- * @return none
- *************************************************************************/
+* @brief
+* The initPreTreatmentMode function initializes the Pre-Treatment mode.
+* @details Inputs: none
+* @details Outputs: Resets the Treatment Parameters session and sets the initial
+* Pre-Treatment sub-state.
+* @return none
+**************************************************************************/
 void initPreTreatmentMode( void )
 {
-    testTimeRemove = 0;
+    // Start a fresh Treatment Parameters session for this run.
+    resetTreatmentParameters();
+    currentPreTreatmentState = TD_PRE_TREATMENT_CONFIRM_RX_STATE;
 }
 
 /*********************************************************************//**
- * @brief
- * The transitionToPreTreatmentMode function prepares for transition to pre-treatment
- * mode.
- * @details \b Inputs: none
- * @details \b Outputs: none
- * @return initial state
- *************************************************************************/
+* @brief
+* The transitionToPreTreatmentMode function prepares the system for
+* entry into Pre-Treatment mode.
+* @details Inputs:  none
+* @details Outputs: Initializes mode specific state and returns the starting
+* Pre-Treatment sub-state.
+* @return Initial Pre-Treatment sub-state
+**************************************************************************/
 U32  transitionToPreTreatmentMode( void )
 {
     initPreTreatmentMode();
 
-    testTimeRemove = getMSTimerCount();
+    return (U32)currentPreTreatmentState;
+}
 
-    return 0;
+/*********************************************************************//**
+ * @brief
+ * The execPreTreatmentMode function executes the Pre-Treatment
+ * mode state machine.
+ * @details Inputs: stop button status and system conditions via helpers.
+ * @details Outputs: Advances the Pre-Treatment sub-state and
+ * previously received user confirmations.
+ * @return current Pre-Treatment sub-state.
+ *************************************************************************/
+U32 execPreTreatmentMode( void )
+{
+    BOOL stop = isStopButtonPressed();
+
+    if ( TRUE == stop )
+    {
+        activateAlarmNoData( ALARM_ID_TD_TREATMENT_STOPPED_BY_USER );
+    }
+
+    // Execute mode state machine
+    switch ( currentPreTreatmentState )
+    {
+        case TD_PRE_TREATMENT_WATER_SAMPLE_STATE:
+            // currentPreTreatmentState = handleWaterSampleState();
+            break;
+
+        case TD_PRE_TREATMENT_SELF_TEST_CONSUMABLE_STATE:
+            // currentPreTreatmentState = handleSelfTestConsumableState();
+            break;
+
+        case TD_PRE_TREATMENT_SELF_TEST_NO_CART_STATE:
+            // currentPreTreatmentState = handleSelfTestNoCartState();
+            break;
+
+        case TD_PRE_TREATMENT_CART_INSTALL_STATE:
+            // currentPreTreatmentState = handleInstallState();
+            break;
+
+        case TD_PRE_TREATMENT_SELF_TEST_DRY_STATE:
+            // currentPreTreatmentState = handleSelfTestDryState();
+            break;
+
+        case TD_PRE_TREATMENT_PRIME_STATE:
+            // currentPreTreatmentState = handlePrimeState();
+            break;
+
+        case TD_PRE_TREATMENT_RECIRCULATE_STATE:
+            // currentPreTreatmentState = handleRecirculateState();
+            break;
+
+        case TD_PRE_TREATMENT_CONFIRM_RX_STATE:
+            // Confirm Rx state
+            currentPreTreatmentState = handleRxState();
+            break;
+
+        case TD_PRE_TREATMENT_PATIENT_CONNECTION_STATE:
+            // currentPreTreatmentState = handlePatientConnectionState();
+            break;
+
+        default:
+            SET_ALARM_WITH_2_U32_DATA( ALARM_ID_TD_SOFTWARE_FAULT, SW_FAULT_ID_MODE_PRE_TREATMENT_INVALID_STATE, (U32)currentPreTreatmentState );
+            break;
+    }
+
+    return (U32)currentPreTreatmentState;
 }
 
 /*********************************************************************//**
  * @brief
- * The execPreTreatmentMode function executes the Pre Treatment Mode state machine.
- * @details \b Alarm: TODO fill up once the exec function is complete
- * the stop button
- * @details \b Inputs: TODO fill up once the exec function is complete
- * @details \b Outputs: TODO fill up once the exec function is complete
- * @return current state (sub-mode)
+ * The handleRxState function executes the Confirm Rx pre-treatment step.
+ * @details Inputs: none
+ * @details Outputs: Requests transition to Treatment mode when the prescription
+ * is valid and confirmed otherwise remains in Confirm Rx.
+ * @return next Pre-Treatment mode sub-state.
  *************************************************************************/
-U32  execPreTreatmentMode( void )
+static TD_PRE_TREATMENT_MODE_STATE_T handleRxState( void )
 {
-    if ( TRUE == didTimeout( testTimeRemove, 10000 ) ) // TODO temporary test code to just transition to treatment mode
+    BOOL paramsValid     = getValidTreatParamsReceived();
+    BOOL paramsConfirmed = getTreatParamsConfirmed();
+    TD_PRE_TREATMENT_MODE_STATE_T state = TD_PRE_TREATMENT_CONFIRM_RX_STATE;
+
+    // Valid + confirmed – move to next state: Patient Connection
+    if ( ( TRUE == paramsValid ) && ( TRUE == paramsConfirmed ) )
     {
+        // TODO: when additional Pre-Treatment states are implemented, change to TD_PRE_TREATMENT_PATIENT_CONNECTION_STATE.
+        // state = TD_PRE_TREATMENT_PATIENT_CONNECTION_STATE;
         requestNewOperationMode( MODE_TREA );
     }
 
-    return 0;
+    return state;
 }
 
 /**@}*/
-
-