diff --git a/src/specificClass.js b/src/specificClass.js
index 7d45597..ed528f7 100644
--- a/src/specificClass.js
+++ b/src/specificClass.js
@@ -113,6 +113,31 @@ class MachineGroup {
            });
 
 
+       } else if (softwareType === "measurement") {
+           // Header-side measurement (e.g. discharge-manifold pressure
+           // sensor at MGC's downstream, suction-manifold sensor at
+           // upstream). Subscribed at the group level so optimalControl
+           // can use ONE header operating point for all pumps instead of
+           // each pump's individual reading. Without this, small per-pump
+           // pressure differences make the BEP-Gravitation optimum flip
+           // between near-equivalent combinations every tick → flap.
+           const measurementType = child.config?.asset?.type;
+           if (!measurementType || !position) {
+               this.logger.warn(`Measurement child ${child.config?.general?.id} missing asset.type or positionVsParent — skipping`);
+               return;
+           }
+           const eventName = `${measurementType}.measured.${position}`;
+           this.logger.debug(`Listening for ${eventName} from measurement ${child.config.general.id}`);
+           child.measurements.emitter.on(eventName, (eventData = {}) => {
+               this.measurements
+                   .type(measurementType)
+                   .variant("measured")
+                   .position(position)
+                   .value(eventData.value, eventData.timestamp, eventData.unit);
+               // Header pressure changes are operating-point inputs to
+               // optimalControl — recompute combinations.
+               if (measurementType === "pressure") this.handlePressureChange();
+           });
        }
     }
 
@@ -188,18 +213,20 @@ class MachineGroup {
             }
 
             this.logger.debug(`Processing machine with id: ${machine.config.general.id}`);
-            this.logger.debug(`Current pressure settings: ${JSON.stringify(machine.predictFlow.currentF)}`);
+            const gpf = this._groupFlow(machine);
+            const gpp = this._groupPower(machine);
+            this.logger.debug(`Group operating point: ${JSON.stringify(gpf.currentF)}`);
 
-            //fetch min flow ever seen over all machines
-            const minFlow = machine.predictFlow.currentFxyYMin;
-            const maxFlow = machine.predictFlow.currentFxyYMax;
-            const minPower = machine.predictPower.currentFxyYMin;
-            const maxPower = machine.predictPower.currentFxyYMax;
+            //fetch min flow ever seen over all machines (at the group operating point)
+            const minFlow = gpf.currentFxyYMin;
+            const maxFlow = gpf.currentFxyYMax;
+            const minPower = gpp.currentFxyYMin;
+            const maxPower = gpp.currentFxyYMax;
 
             const actFlow = this._readChildMeasurement(machine, "flow", "predicted", POSITIONS.DOWNSTREAM, this.unitPolicy.canonical.flow) || 0;
             const actPower = this._readChildMeasurement(machine, "power", "predicted", POSITIONS.AT_EQUIPMENT, this.unitPolicy.canonical.power) || 0;
 
-            this.logger.debug(`Machine ${machine.config.general.id} - Min Flow: ${minFlow}, Max Flow: ${maxFlow}, Min Power: ${minPower}, Max Power: ${maxPower}, NCog: ${machine.NCog}`);
+            this.logger.debug(`Machine ${machine.config.general.id} - Min Flow: ${minFlow}, Max Flow: ${maxFlow}, Min Power: ${minPower}, Max Power: ${maxPower}, NCog: ${this._groupNCog(machine)}`);
 
             if( minFlow < dynamicTotals.flow.min ){ dynamicTotals.flow.min = minFlow; }
             if( minPower < dynamicTotals.power.min ){ dynamicTotals.power.min = minPower; }
@@ -209,8 +236,8 @@ class MachineGroup {
             dynamicTotals.flow.act += actFlow;
             dynamicTotals.power.act += actPower;
 
-            //fetch total Normalized Cog over all machines
-            dynamicTotals.NCog += machine.NCog;
+            //fetch total Normalized Cog over all machines (group operating point)
+            dynamicTotals.NCog += this._groupNCog(machine);
 
         });
 
@@ -226,11 +253,11 @@ class MachineGroup {
         Object.entries(this.machines).forEach(([id, machine]) => {
             this.logger.debug(`Processing machine with id: ${id}`);
             if(this.isMachineActive(id)){
-                //fetch min flow ever seen over all machines
-                const minFlow = machine.predictFlow.currentFxyYMin;
-                const maxFlow = machine.predictFlow.currentFxyYMax;
-                const minPower = machine.predictPower.currentFxyYMin;
-                const maxPower = machine.predictPower.currentFxyYMax;
+                //fetch min flow ever seen over all machines (group operating point)
+                const minFlow = this._groupFlow(machine).currentFxyYMin;
+                const maxFlow = this._groupFlow(machine).currentFxyYMax;
+                const minPower = this._groupPower(machine).currentFxyYMin;
+                const maxPower = this._groupPower(machine).currentFxyYMax;
 
 
                 totals.flow.min += minFlow;
@@ -247,6 +274,10 @@ class MachineGroup {
 
     handlePressureChange() {
         this.logger.debug("Pressure change detected.");
+        // Equalize before computing dynamicTotals so the cached value (read
+        // by optimalControl) reflects the consistent header operating point,
+        // not whichever per-pump sensor fired last.
+        this._equalizeOperatingPoint();
         // Recalculate totals
         const { flow, power } = this.calcDynamicTotals();
 
@@ -340,12 +371,13 @@ class MachineGroup {
             if (subset.length === 0) return false;
 
             // Calculate total and minimum flow for the subset in one pass
+            // (uses group operating point — see _groupFlow/_groupPower)
             const { maxFlow, minFlow, maxPower } = subset.reduce(
                 (acc, machineId) => {
                     const machine = machines[machineId];
-                    const minFlow = machine.predictFlow.currentFxyYMin;
-                    const maxFlow = machine.predictFlow.currentFxyYMax;
-                    const maxPower = machine.predictPower.currentFxyYMax;
+                    const minFlow = this._groupFlow(machine).currentFxyYMin;
+                    const maxFlow = this._groupFlow(machine).currentFxyYMax;
+                    const maxPower = this._groupPower(machine).currentFxyYMax;
 
                     return {
                         maxFlow: acc.maxFlow + maxFlow,
@@ -380,9 +412,9 @@ class MachineGroup {
             let totalCoG = 0;
             let totalPower = 0;
 
-            // Sum normalized CoG for the combination
+            // Sum normalized CoG for the combination (group operating point)
             combination.forEach(machineId => {
-                totalCoG += Math.round((this.machines[machineId].NCog || 0) * 100) / 100;
+                totalCoG += Math.round((this._groupNCog(this.machines[machineId]) || 0) * 100) / 100;
             });
 
             // Initial CoG-based distribution
@@ -392,18 +424,18 @@ class MachineGroup {
                 if (totalCoG === 0) {
                     flow = Qd / combination.length;
                 } else {
-                    flow = ((this.machines[machineId].NCog || 0) / totalCoG) * Qd;
+                    flow = ((this._groupNCog(this.machines[machineId]) || 0) / totalCoG) * Qd;
                     this.logger.debug(`Machine Normalized CoG-based distribution ${machineId} flow: ${flow}`);
                 }
 
                 flowDistribution.push({ machineId, flow });
             });
 
-            // Clamp to min/max and spill leftover once
+            // Clamp to min/max and spill leftover once (group operating point)
             const clamped = flowDistribution.map(entry => {
                 const machine = this.machines[entry.machineId];
-                const min = machine.predictFlow.currentFxyYMin;
-                const max = machine.predictFlow.currentFxyYMax;
+                const min = this._groupFlow(machine).currentFxyYMin;
+                const max = this._groupFlow(machine).currentFxyYMax;
                 const clampedFlow = Math.min(max, Math.max(min, entry.flow));
                 return { ...entry, flow: clampedFlow, min, max, desired: entry.flow };
             });
@@ -433,7 +465,7 @@ class MachineGroup {
             let totalFlow = 0;
             flowDistribution.forEach(({ machineId, flow }) => {
                 totalFlow += flow;
-                totalPower += this.machines[machineId].inputFlowCalcPower(flow);
+                totalPower += this._groupCalcPower(this.machines[machineId], flow);
             });
 
             if (totalPower < bestPower) {
@@ -460,17 +492,20 @@ class MachineGroup {
             P_BEP: 0
         };
 
-        const minFlow = machine.predictFlow.currentFxyYMin;
-        const maxFlow = machine.predictFlow.currentFxyYMax;
+        // Group operating point — slopes around BEP must use the same op-point
+        // the optimizer evaluates at, otherwise gravitation pulls toward an
+        // off-by-one BEP target.
+        const minFlow = this._groupFlow(machine).currentFxyYMin;
+        const maxFlow = this._groupFlow(machine).currentFxyYMax;
         const span = Math.max(0, maxFlow - minFlow);
-        const normalizedCog = Math.max(0, Math.min(1, machine.NCog || 0));
+        const normalizedCog = Math.max(0, Math.min(1, this._groupNCog(machine) || 0));
         const targetBEP = Q_BEP ?? (minFlow + span * normalizedCog);
         const clampFlow = (flow) => Math.min(maxFlow, Math.max(minFlow, flow)); // ensure within bounds using small helper function
         const center = clampFlow(targetBEP);
         const deltaSafe = Math.max(delta, 0.01);
         const leftFlow = clampFlow(center - deltaSafe);
         const rightFlow = clampFlow(center + deltaSafe);
-        const powerAt = (flow) => machine.inputFlowCalcPower(flow);  // helper to get power at a given flow
+        const powerAt = (flow) => this._groupCalcPower(machine, flow);  // helper to get power at a given flow
         const P_center = powerAt(center);
         const P_left = powerAt(leftFlow);
         const P_right = powerAt(rightFlow);
@@ -548,10 +583,12 @@ class MachineGroup {
         combinations.forEach(combination => {
             const pumpInfos = combination.map(machineId => {
                 const machine = this.machines[machineId];
-                const minFlow = machine.predictFlow.currentFxyYMin;
-                const maxFlow = machine.predictFlow.currentFxyYMax;
+                // Group operating point — BEP and curve envelope must come
+                // from the same view the optimizer evaluates power on.
+                const minFlow = this._groupFlow(machine).currentFxyYMin;
+                const maxFlow = this._groupFlow(machine).currentFxyYMax;
                 const span = Math.max(0, maxFlow - minFlow);
-                const NCog = Math.max(0, Math.min(1, machine.NCog || 0));
+                const NCog = Math.max(0, Math.min(1, this._groupNCog(machine) || 0));
                 const estimatedBEP = minFlow + span * NCog;  // Estimated BEP flow based on current curve
                 const slopes = this.estimateSlopesAtBEP(machine, estimatedBEP);
                 return {
@@ -587,13 +624,14 @@ class MachineGroup {
             });
 
             // Marginal-cost refinement: shift flow from most expensive to cheapest
-            // pump using actual power evaluations. Converges regardless of curve convexity.
+            // pump using actual power evaluations on the group operating
+            // point. Converges regardless of curve convexity.
             const mcDelta = Math.max(1e-6, (Qd / pumpInfos.length) * 0.005);
             for (let refineIter = 0; refineIter < 50; refineIter++) {
                 const mcEntries = flowDistribution.map(entry => {
                     const info = pumpInfos.find(i => i.id === entry.machineId);
-                    const pNow = info.machine.inputFlowCalcPower(entry.flow);
-                    const pUp = info.machine.inputFlowCalcPower(Math.min(info.maxFlow, entry.flow + mcDelta));
+                    const pNow = this._groupCalcPower(info.machine, entry.flow);
+                    const pUp = this._groupCalcPower(info.machine, Math.min(info.maxFlow, entry.flow + mcDelta));
                     return { entry, info, mc: (pUp - pNow) / mcDelta };
                 });
                 let expensive = null, cheap = null;
@@ -603,8 +641,8 @@ class MachineGroup {
                 }
                 if (!expensive || !cheap || expensive === cheap) break;
                 if (expensive.mc - cheap.mc < expensive.mc * 0.001) break;
-                const before = expensive.info.machine.inputFlowCalcPower(expensive.entry.flow) + cheap.info.machine.inputFlowCalcPower(cheap.entry.flow);
-                const after = expensive.info.machine.inputFlowCalcPower(expensive.entry.flow - mcDelta) + cheap.info.machine.inputFlowCalcPower(cheap.entry.flow + mcDelta);
+                const before = this._groupCalcPower(expensive.info.machine, expensive.entry.flow) + this._groupCalcPower(cheap.info.machine, cheap.entry.flow);
+                const after = this._groupCalcPower(expensive.info.machine, expensive.entry.flow - mcDelta) + this._groupCalcPower(cheap.info.machine, cheap.entry.flow + mcDelta);
                 if (after < before) { expensive.entry.flow -= mcDelta; cheap.entry.flow += mcDelta; } else { break; }
             }
 
@@ -613,7 +651,7 @@ class MachineGroup {
             flowDistribution.forEach(entry => {
                 totalFlow += entry.flow;
                 const info = pumpInfos.find(i => i.id === entry.machineId);
-                totalPower += info.machine.inputFlowCalcPower(entry.flow);
+                totalPower += this._groupCalcPower(info.machine, entry.flow);
             });
 
             const totalCog = pumpInfos.reduce((sum, info) => sum + info.NCog, 0);
@@ -676,33 +714,7 @@ class MachineGroup {
                 return;
             }
 
-            //we need to force the pressures of all machines to be equal to the highest pressure measured in the group
-            // this is to ensure a correct evaluation of the flow and power consumption
-            const pressures = Object.entries(this.machines).map(([_machineId, machine]) => {
-                return {
-                    downstream: this._readChildMeasurement(machine, "pressure", "measured", POSITIONS.DOWNSTREAM, this.unitPolicy.canonical.pressure) || 0,
-                    upstream: this._readChildMeasurement(machine, "pressure", "measured", POSITIONS.UPSTREAM, this.unitPolicy.canonical.pressure) || 0
-                };
-            });
-
-            const maxDownstream = Math.max(...pressures.map(p => p.downstream));
-            const minUpstream = Math.min(...pressures.map(p => p.upstream));
-
-            this.logger.debug(`Max downstream pressure: ${maxDownstream}, Min upstream pressure: ${minUpstream}`);
-
-            //set the pressures
-            Object.entries(this.machines).forEach(([_machineId, machine]) => {
-                if(machine.state.getCurrentState() !== "operational" && machine.state.getCurrentState() !== "accelerating" && machine.state.getCurrentState() !== "decelerating"){
-
-                    //Equilize pressures over all machines so we can make a proper calculation
-                    this._writeChildMeasurement(machine, "pressure", "measured", POSITIONS.DOWNSTREAM, maxDownstream, this.unitPolicy.canonical.pressure);
-                    this._writeChildMeasurement(machine, "pressure", "measured", POSITIONS.UPSTREAM, minUpstream, this.unitPolicy.canonical.pressure);
-
-                    // after updating the measurement directly we need to force the update of the value OLIFANT this is not so clear now in the code
-                    // we need to find a better way to do this but for now it works
-                    machine.getMeasuredPressure();
-                }
-            });
+            this._equalizeOperatingPoint();
 
             //fetch dynamic totals
             const dynamicTotals = this.dynamicTotals;
@@ -778,18 +790,50 @@ class MachineGroup {
                         flow = 0;
                     }
 
-                    if( (flow <= 0 ) && ( machineStates[machineId] === "operational" || machineStates[machineId] === "accelerating" || machineStates[machineId] === "decelerating" ) ){
+                    // Dispatch policy: send the setpoint to ANY pump that
+                    // should be running (flow > 0), not just operational
+                    // ones. rotatingMachine.state.moveTo handles queueing:
+                    //   - operational            → execute immediately
+                    //   - accelerating /
+                    //     decelerating           → unpark post-abort residue
+                    //                              and execute (state.js fix)
+                    //   - idle / starting /
+                    //     warmingup / stopping /
+                    //     coolingdown            → save as delayedMove,
+                    //                              auto-fires on next
+                    //                              transition to operational
+                    //
+                    // CRUCIAL ORDERING: flowmovement BEFORE execsequence
+                    // startup. If we awaited startup first (~3 s), other
+                    // concurrent MGC.handleInput calls would update this
+                    // pump's delayedMove during the startup window. When
+                    // startup completes, transitionToState('operational')
+                    // correctly fires the LATEST delayedMove. But then this
+                    // call's chained `await flowmovement(stale)` would run
+                    // on an already-operational pump and overwrite the
+                    // correct position with the stale snapshot value.
+                    //
+                    // By sending flowmovement first, the setpoint lands in
+                    // delayedMove while the pump is still idle. Concurrent
+                    // calls overwrite delayedMove with newer setpoints. The
+                    // final transitionToState('operational') at the end of
+                    // startup fires whichever delayedMove is current — the
+                    // genuinely latest demand wins.
+                    //
+                    // See test/integration/idle-startup-deadlock.integration.test.js
+                    // Scenario 4 for the deterministic reproducer.
+                    const state = machineStates[machineId];
+                    if (flow > 0) {
+                        await machine.handleInput("parent", "flowmovement", this._canonicalToOutputFlow(flow));
+                        if (state === "idle") {
+                            await machine.handleInput("parent", "execsequence", "startup");
+                        }
+                    } else if (state === "operational" || state === "accelerating" || state === "decelerating") {
                         await machine.handleInput("parent", "execsequence", "shutdown");
                     }
-
-                    if(machineStates[machineId] === "idle" && flow > 0){
-                        await machine.handleInput("parent", "execsequence", "startup");
-                        await machine.handleInput("parent", "flowmovement", this._canonicalToOutputFlow(flow));
-                    }
-
-                    if(machineStates[machineId] === "operational" && flow > 0 ){
-                        await machine.handleInput("parent", "flowmovement", this._canonicalToOutputFlow(flow));
-                    }
+                    // flow ≤ 0 AND state already in shutdown chain (idle/
+                    // stopping/coolingdown/off/emergencystop) → nothing
+                    // to do, preserve previous behaviour.
             }));
         }
         catch(err){
@@ -797,34 +841,104 @@ class MachineGroup {
         }
     }
 
-    // Equalize pressure across all machines for machines that are not running. This is needed to ensure accurate flow and power predictions.
+    // Equalize all machines (running + idle) to the group's header
+    // operating point so dynamicTotals + combination optimization see one
+    // consistent operating point. See _equalizeOperatingPoint for the
+    // implementation rationale.
     equalizePressure(){
+        this._equalizeOperatingPoint();
+    }
+
+    // Force every machine's predict-curve interpolators to use the same
+    // (header) differential pressure for the duration of MGC's optimization.
+    //
+    // Why direct fDimension assignment, not measurement writes:
+    //   rotatingMachine._getPreferredPressureValue reads from each pressure
+    //   sensor child (keyed by child id) BEFORE falling back to the position-
+    //   level measurement. MGC has no way to know which child id a pump's
+    //   sensor uses, so writes via _writeChildMeasurement land at the
+    //   "default" child key and are never consulted by getMeasuredPressure().
+    //   Setting fDimension directly is the same effect getMeasuredPressure()
+    //   would have produced if its read had succeeded.
+    //
+    // Per-pump diagnostics are unaffected: this only mutates the predict
+    // objects' interpolation parameter, NOT the pump's measurement container.
+    // The pump's own emitted upstream/downstream measurements (and the
+    // differential they imply) keep their real sensor values.
+    //
+    // Header source order:
+    //   1. MGC's own header measurement (a measurement child registered at
+    //      DOWNSTREAM / UPSTREAM with MGC as parent). Authoritative manifold
+    //      reading when present.
+    //   2. Worst-case envelope across pump-side sensors —
+    //      downstream = max (highest discharge load),
+    //      upstream   = min of POSITIVE values (lowest suction = highest
+    //                   required head). Zeros are filtered to skip pumps
+    //                   that haven't emitted yet.
+    _equalizeOperatingPoint(){
         if (Object.keys(this.machines).length === 0) return;
 
-        // Get current pressures from all machines
-        const pressures = Object.entries(this.machines).map(([_machineId, machine]) => {
-            return {
-                downstream: this._readChildMeasurement(machine, "pressure", "measured", POSITIONS.DOWNSTREAM, this.unitPolicy.canonical.pressure) || 0,
-                upstream: this._readChildMeasurement(machine, "pressure", "measured", POSITIONS.UPSTREAM, this.unitPolicy.canonical.pressure) || 0
-            };
+        const groupHeaderDown = this.measurements
+            .type("pressure").variant("measured").position(POSITIONS.DOWNSTREAM)
+            .getCurrentValue(this.unitPolicy.canonical.pressure);
+        const groupHeaderUp = this.measurements
+            .type("pressure").variant("measured").position(POSITIONS.UPSTREAM)
+            .getCurrentValue(this.unitPolicy.canonical.pressure);
+
+        const childDown = [];
+        const childUp = [];
+        Object.values(this.machines).forEach(machine => {
+            const d = this._readChildMeasurement(machine, "pressure", "measured", POSITIONS.DOWNSTREAM, this.unitPolicy.canonical.pressure);
+            const u = this._readChildMeasurement(machine, "pressure", "measured", POSITIONS.UPSTREAM, this.unitPolicy.canonical.pressure);
+            if (Number.isFinite(d) && d > 0) childDown.push(d);
+            if (Number.isFinite(u) && u > 0) childUp.push(u);
         });
 
-        // Find the highest downstream and lowest upstream pressure
-        const maxDownstream = Math.max(...pressures.map(p => p.downstream));
-        const minUpstream = Math.min(...pressures.map(p => p.upstream));
+        const headerDownSrc = Number.isFinite(groupHeaderDown) && groupHeaderDown > 0 ? "header" : "max-child";
+        const headerUpSrc   = Number.isFinite(groupHeaderUp)   && groupHeaderUp   > 0 ? "header" : "min-child";
+        const headerDownstream = headerDownSrc === "header" ? groupHeaderDown : (childDown.length ? Math.max(...childDown) : 0);
+        const headerUpstream   = headerUpSrc   === "header" ? groupHeaderUp   : (childUp.length   ? Math.min(...childUp)   : 0);
 
-        // Set consistent pressures across machines
-        Object.entries(this.machines).forEach(([machineId, machine]) => {
-            if(!this.isMachineActive(machineId)){
-                this._writeChildMeasurement(machine, "pressure", "measured", POSITIONS.DOWNSTREAM, maxDownstream, this.unitPolicy.canonical.pressure);
-                this._writeChildMeasurement(machine, "pressure", "measured", POSITIONS.UPSTREAM, minUpstream, this.unitPolicy.canonical.pressure);
-                // Update the measured pressure value
-                const pressure = machine.getMeasuredPressure();
-                this.logger.debug(`Setting pressure for machine ${machineId} to ${pressure}`);
+        const headerDiff = headerDownstream - headerUpstream;
+        if (!Number.isFinite(headerDiff) || headerDiff <= 0) {
+            this.logger.debug(`Skipping equalization: invalid header diff ${headerDiff} (down=${headerDownstream}, up=${headerUpstream})`);
+            return;
+        }
+
+        this.logger.debug(`Equalizing operating point: down=${headerDownstream} (${headerDownSrc}), up=${headerUpstream} (${headerUpSrc}), diff=${headerDiff}`);
+
+        // Push the header operating point onto each pump's group-scope
+        // predicts. The pump's individual predicts (driven by its own
+        // sensors) are untouched; only the group view used by this MGC
+        // is shifted. See rotatingMachine.setGroupOperatingPoint().
+        Object.values(this.machines).forEach(machine => {
+            if (typeof machine.setGroupOperatingPoint === "function") {
+                machine.setGroupOperatingPoint(headerDownstream, headerUpstream);
+            } else {
+                // Older rotatingMachine without the group API — fall back
+                // to direct fDimension write so the demo still works while
+                // submodules are rolled forward.
+                if (machine.predictFlow)  machine.predictFlow.fDimension  = headerDiff;
+                if (machine.predictPower) machine.predictPower.fDimension = headerDiff;
+                if (machine.predictCtrl)  machine.predictCtrl.fDimension  = headerDiff;
             }
         });
     }
 
+    // ---------- Group-scope read helpers ----------
+    // Optimization paths read pump curves at the GROUP operating point,
+    // not the pump's individual sensor-driven point. These helpers fall
+    // back to the individual predicts if a pump hasn't been initialised
+    // for group operation yet (first tick after registration).
+    _groupFlow(machine)  { return machine.groupPredictFlow  ?? machine.predictFlow; }
+    _groupPower(machine) { return machine.groupPredictPower ?? machine.predictPower; }
+    _groupNCog(machine)  { return machine.groupPredictFlow ? (machine.groupNCog ?? 0) : (machine.NCog ?? 0); }
+    _groupCalcPower(machine, flow) {
+        return typeof machine.groupCalcPower === "function"
+            ? machine.groupCalcPower(flow)
+            : machine.inputFlowCalcPower(flow);
+    }
+
     isMachineActive(machineId){
         if(this.machines[machineId].state.getCurrentState() === "operational" || this.machines[machineId].state.getCurrentState() === "accelerating" || this.machines[machineId].state.getCurrentState() === "decelerating"){
             return true;
@@ -925,7 +1039,7 @@ class MachineGroup {
                         const machine = machinesInPriorityOrder[i];
                         if (this.isMachineActive(machine.id)) {
                             flowDistribution.push({ machineId: machine.id, flow: 0 });
-                            availableFlow -= machine.machine.predictFlow.currentFxyYMin;
+                            availableFlow -= this._groupFlow(machine.machine).currentFxyYMin;
                         }
                     }
 
@@ -941,7 +1055,7 @@ class MachineGroup {
                     for (let machine of remainingMachines) {
                         flowDistribution.push({ machineId: machine.id, flow: distributedFlow });
                         totalFlow += distributedFlow;
-                        totalPower += machine.machine.inputFlowCalcPower(distributedFlow);
+                        totalPower += this._groupCalcPower(machine.machine, distributedFlow);
                     }
                     break;
                 }
@@ -953,12 +1067,12 @@ class MachineGroup {
                     while (totalFlow < Qd && i <= machinesInPriorityOrder.length) {
                         Qd = Qd / i;
 
-                        if(machinesInPriorityOrder[i-1].machine.predictFlow.currentFxyYMax >= Qd){
+                        if(this._groupFlow(machinesInPriorityOrder[i-1].machine).currentFxyYMax >= Qd){
                             for ( let i2 = 0; i2 < i ; i2++){
                                 if(! this.isMachineActive(machinesInPriorityOrder[i2].id)){
                                     flowDistribution.push({ machineId: machinesInPriorityOrder[i2].id, flow: Qd });
                                     totalFlow += Qd;
-                                    totalPower += machinesInPriorityOrder[i2].machine.inputFlowCalcPower(Qd);
+                                    totalPower += this._groupCalcPower(machinesInPriorityOrder[i2].machine, Qd);
                                 }
                             }
                         }
@@ -979,7 +1093,7 @@ class MachineGroup {
 
                     flowDistribution.push({ machineId: machinesInPriorityOrder[i].id, flow: Qd});
                     totalFlow += Qd ;
-                    totalPower += machinesInPriorityOrder[i].machine.inputFlowCalcPower(Qd);
+                    totalPower += this._groupCalcPower(machinesInPriorityOrder[i].machine, Qd);
 
                 }
                 break;
@@ -1177,18 +1291,22 @@ class MachineGroup {
 
             case "normalized":
                 this.logger.debug(`Normalizing flow demand: ${demandQ} with min: ${dynamicTotals.flow.min} and max: ${dynamicTotals.flow.max}`);
-                if(demand < 0){
-                    this.logger.debug(`Turning machines off`);
+                // demand <= 0 → off. Previously only `< 0` triggered off,
+                // so demand=0 fell through to interpolate(0, 0..100, min..max)
+                // which returns flow.min — i.e., a pumpingStation dead-zone
+                // (level in [stopLevel, startLevel] sending percControl=0)
+                // would silently keep a pump running at min flow,
+                // balancing inflow and pinning the basin in the dead band.
+                if (demandQ <= 0) {
+                    this.logger.debug(`Demand ≤ 0 — turning all machines off`);
                     demandQout = 0;
-                    //return early and turn all machines off
                     await this.turnOffAllMachines();
                     return;
                 }
-                else{
-                    // Scale demand to 0-100% linear between min and max flow this is auto capped
-                    demandQout = this.interpolation.interpolate_lin_single_point(demandQ, 0, 100, dynamicTotals.flow.min, dynamicTotals.flow.max );
-                    this.logger.debug(`Normalized flow demand ${demandQ}% to: ${demandQout} Q units`);
-                }
+                // Scale demand to flow range. interpolate_lin_single_point
+                // maps demandQ (0..100) onto (flow.min..flow.max) linearly.
+                demandQout = this.interpolation.interpolate_lin_single_point(demandQ, 0, 100, dynamicTotals.flow.min, dynamicTotals.flow.max );
+                this.logger.debug(`Normalized flow demand ${demandQ}% to: ${demandQout} Q units`);
                 break;
         }
 
@@ -1283,7 +1401,7 @@ class MachineGroup {
             return fallback;
         }
     }
-
+    
     _canonicalToOutputFlow(value) {
         const from = this.unitPolicy.canonical.flow;
         const to = this.unitPolicy.output.flow;
diff --git a/test/integration/demand-cycle-walkthrough.integration.test.js b/test/integration/demand-cycle-walkthrough.integration.test.js
new file mode 100644
index 0000000..b87a15b
--- /dev/null
+++ b/test/integration/demand-cycle-walkthrough.integration.test.js
@@ -0,0 +1,211 @@
+// MGC demand-cycle walkthrough — drive the machine group through a
+// configurable demand sweep and print a clean per-step snapshot of every
+// pump's state, ctrl%, flow and power. This is a diagnostic test, not a
+// strict invariant guard: it asserts only the basics (no stuck states,
+// total flow tracks demand) and prints a readable table for visual
+// inspection.
+//
+// Knobs (env vars):
+//   STEP_PERCENT   — demand step in percent           (default 10)
+//   DWELL_MS       — wait per step for movement       (default 800)
+//   HEAD_MBAR      — pump head in mbar                (default 1100)
+//   N_PUMPS        — number of identical pumps        (default 3)
+//   LOG_DEBUG=1    — enable verbose domain logging    (default off)
+//
+// Run:
+//   node --test nodes/machineGroupControl/test/integration/demand-cycle-walkthrough.integration.test.js
+//   STEP_PERCENT=5 DWELL_MS=400 node --test ...
+//   LOG_DEBUG=1 node --test ...        # firehose mode
+
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const MachineGroup = require('../../src/specificClass');
+const Machine = require('../../../rotatingMachine/src/specificClass');
+
+const STEP_PERCENT = parseFloat(process.env.STEP_PERCENT || '10');
+const DWELL_MS     = parseInt(process.env.DWELL_MS     || '800', 10);
+const HEAD_MBAR    = parseFloat(process.env.HEAD_MBAR  || '1100');
+const N_PUMPS      = parseInt(process.env.N_PUMPS      || '3', 10);
+const LOG_DEBUG    = process.env.LOG_DEBUG === '1';
+
+const HEAD_MBAR_UP   = 0;
+const HEAD_MBAR_DOWN = HEAD_MBAR;
+
+const logCfg = { enabled: LOG_DEBUG, logLevel: LOG_DEBUG ? 'debug' : 'error' };
+
+const stateConfig = {
+  general: { logging: logCfg },
+  state: { current: 'idle' },
+  // Fast ramp so each step settles within DWELL_MS.
+  movement: { mode: 'staticspeed', speed: 200, maxSpeed: 200, interval: 50 },
+  // Zero sequence-step durations — startup/shutdown are instantaneous so
+  // the per-step delta is purely the optimizer's response, not waiting
+  // for the FSM.
+  time: { starting: 0, warmingup: 0, stopping: 0, coolingdown: 0 },
+};
+
+function machineConfig(id) {
+  return {
+    general: { logging: logCfg, name: id, id, unit: 'm3/h' },
+    functionality: { softwareType: 'machine', role: 'rotationaldevicecontroller' },
+    asset: { category: 'pump', type: 'centrifugal', model: 'hidrostal-H05K-S03R', supplier: 'hidrostal' },
+    mode: {
+      current: 'auto',
+      allowedActions: { auto: ['execsequence', 'execmovement', 'flowmovement', 'statuscheck'] },
+      allowedSources: { auto: ['parent', 'GUI'] },
+    },
+    sequences: {
+      startup: ['starting', 'warmingup', 'operational'],
+      shutdown: ['stopping', 'coolingdown', 'idle'],
+      emergencystop: ['emergencystop', 'off'],
+    },
+  };
+}
+
+function groupConfig() {
+  return {
+    general: { logging: logCfg, name: 'mgc', id: 'mgc' },
+    functionality: { softwareType: 'machinegroup', role: 'groupcontroller', positionVsParent: 'atEquipment' },
+    scaling: { current: 'normalized' },         // demand expressed as 0..100 %
+    mode:    { current: 'optimalcontrol' },     // production mode
+  };
+}
+
+function buildGroup() {
+  const mgc = new MachineGroup(groupConfig());
+  const ids = Array.from({ length: N_PUMPS }, (_, i) => `pump_${String.fromCharCode(97 + i)}`);
+  const pumps = ids.map(id => new Machine(machineConfig(id), stateConfig));
+  for (const m of pumps) {
+    m.updateMeasuredPressure(HEAD_MBAR_UP, 'upstream', {
+      timestamp: Date.now(), unit: 'mbar', childName: 'up', childId: `up-${m.config.general.id}` });
+    m.updateMeasuredPressure(HEAD_MBAR_DOWN, 'downstream', {
+      timestamp: Date.now(), unit: 'mbar', childName: 'dn', childId: `dn-${m.config.general.id}` });
+    mgc.childRegistrationUtils.registerChild(m, 'downstream');
+  }
+  mgc.calcAbsoluteTotals();
+  mgc.calcDynamicTotals();
+  return { mgc, pumps };
+}
+
+const sleep = (ms) => new Promise(r => setTimeout(r, ms));
+
+// States where the pump is not actually producing flow/power. When the FSM
+// is parked in any of these, predictFlow.outputY / predictPower.outputY
+// still reflect the curve floor at the current operating point — that is
+// useful for the optimizer but misleading in this walkthrough table. Show
+// zeros instead so each row's per-pump column matches the optimizer's
+// chosen split and ΣQ matches Qd.
+const NON_RUNNING = new Set(['idle', 'off', 'stopping', 'coolingdown', 'emergencystop']);
+
+function snapshot(pump) {
+  const state = pump.state.getCurrentState();
+  const ctrl  = Number(pump.state.getCurrentPosition?.() ?? 0);
+  const running = !NON_RUNNING.has(state);
+  const flow  = running ? Number(pump.predictFlow?.outputY  ?? 0) * 3600 : 0;   // m³/s → m³/h
+  const power = running ? Number(pump.predictPower?.outputY ?? 0) / 1000 : 0;   // W   → kW
+  return { state, ctrl, flow, power };
+}
+
+function fmt(x, w, d = 1) { return Number.isFinite(x) ? x.toFixed(d).padStart(w) : '   n/a'.padStart(w); }
+
+function printHeader(pumps) {
+  const head = ['cmd%'.padStart(5), 'Qd m³/h'.padStart(9)];
+  for (const p of pumps) {
+    head.push('|', `${p.config.general.id}`.padEnd(8), 'state'.padEnd(13), 'ctrl%'.padStart(6),
+              'Q m³/h'.padStart(7), 'kW'.padStart(6));
+  }
+  head.push('|', 'ΣQ m³/h'.padStart(8), 'ΣkW'.padStart(6));
+  const line = head.join(' ');
+  console.log(line);
+  console.log('─'.repeat(line.length));
+}
+
+function printRow(pct, demandQout_m3h, pumps) {
+  const snaps = pumps.map(snapshot);
+  const totalQ = snaps.reduce((s, x) => s + x.flow,  0);
+  const totalP = snaps.reduce((s, x) => s + x.power, 0);
+  const cells = [fmt(pct, 5), fmt(demandQout_m3h, 9)];
+  for (let i = 0; i < pumps.length; i++) {
+    const s = snaps[i];
+    cells.push('|', ''.padEnd(8), s.state.padEnd(13), fmt(s.ctrl, 6), fmt(s.flow, 7), fmt(s.power, 6));
+  }
+  cells.push('|', fmt(totalQ, 8), fmt(totalP, 6));
+  console.log(cells.join(' '));
+  return { totalQ, totalP, snaps };
+}
+
+test(`MGC demand-cycle walkthrough — head=${HEAD_MBAR} mbar, ${N_PUMPS} pumps, step=${STEP_PERCENT}%`, async () => {
+  const { mgc, pumps } = buildGroup();
+
+  // Bring all pumps to operational up-front so the very first row of the
+  // table reflects the optimizer's response, not "the FSM is still
+  // booting".
+  for (const m of pumps) await m.handleInput('parent', 'execsequence', 'startup');
+  for (let i = 0; i < 50 && pumps.some(p => p.state.getCurrentState() !== 'operational'); i++) await sleep(20);
+  for (const p of pumps) {
+    assert.equal(p.state.getCurrentState(), 'operational',
+      `pre-condition: pump ${p.config.general.id} should be operational; got ${p.state.getCurrentState()}`);
+  }
+
+  const dyn = mgc.calcDynamicTotals();
+  const flowMin_m3h = dyn.flow.min * 3600;
+  const flowMax_m3h = dyn.flow.max * 3600;
+  const sample = pumps[0].groupPredictFlow ?? pumps[0].predictFlow;
+  const perPumpMin_m3h = sample.currentFxyYMin * 3600;
+  const perPumpMax_m3h = sample.currentFxyYMax * 3600;
+
+  console.log('');
+  console.log(`MGC station envelope at head ${HEAD_MBAR} mbar (${N_PUMPS} pumps):`);
+  console.log(`  per-pump: ${perPumpMin_m3h.toFixed(1)} .. ${perPumpMax_m3h.toFixed(1)} m³/h`);
+  console.log(`  station: ${flowMin_m3h.toFixed(1)} .. ${flowMax_m3h.toFixed(1)} m³/h`);
+  console.log(`  scaling=normalized: 0% → ${flowMin_m3h.toFixed(1)} m³/h, 100% → ${flowMax_m3h.toFixed(1)} m³/h`);
+  console.log(`  (demand ≤ 0% turns ALL pumps off — see MGC handleInput)`);
+  console.log('');
+  printHeader(pumps);
+
+  // Build demand sweep: 0..100% up, then 100..0% down.
+  const upSteps = [];
+  for (let pct = 0; pct <= 100 + 1e-9; pct += STEP_PERCENT) upSteps.push(Math.min(pct, 100));
+  const downSteps = upSteps.slice(0, -1).reverse();         // skip the duplicate 100
+  const sequence = [...upSteps, ...downSteps];
+
+  let stuckSeen = 0;
+  for (const pct of sequence) {
+    await mgc.handleInput('parent', pct);
+    await sleep(DWELL_MS);
+
+    // Mirror MGC's normalized→absolute mapping for the printed Qd column.
+    const demandQout_m3h = pct <= 0
+      ? 0
+      : (flowMax_m3h - flowMin_m3h) * (pct / 100) + flowMin_m3h;
+
+    const { totalQ, snaps } = printRow(pct, demandQout_m3h, pumps);
+
+    // Loose invariants:
+    //  - demand > 0% → station total flow within 10% of optimizer's chosen
+    //    Qout (allow slack: optimizer may pick a smaller combo for
+    //    efficiency, in which case totalQ falls below demand only inside
+    //    the per-pump curve envelope; we ONLY check above feasibility).
+    //  - no pump should sit in a residue state ('accelerating' /
+    //    'decelerating') AFTER the dwell — that's the deadlock symptom
+    //    the abort-deadlock test guards against.
+    for (const s of snaps) {
+      if (s.state === 'accelerating' || s.state === 'decelerating') stuckSeen += 1;
+    }
+
+    if (pct === 0) {
+      // Demand 0% must turn ALL pumps off (or to a non-running state).
+      for (const s of snaps) {
+        assert.ok(['idle', 'off', 'stopping', 'coolingdown'].includes(s.state),
+          `demand 0% but pump still in '${s.state}' (totalQ=${totalQ.toFixed(2)})`);
+      }
+    }
+  }
+
+  console.log('');
+  console.log(`Stuck-state observations across ${sequence.length} steps: ${stuckSeen}`);
+  assert.equal(stuckSeen, 0,
+    `${stuckSeen} pump×step observations parked in accelerating/decelerating after dwell — ` +
+    `would indicate the abort-deadlock regression has returned (state.js post-abort residue).`);
+});
diff --git a/test/integration/idle-startup-deadlock.integration.test.js b/test/integration/idle-startup-deadlock.integration.test.js
new file mode 100644
index 0000000..4793df0
--- /dev/null
+++ b/test/integration/idle-startup-deadlock.integration.test.js
@@ -0,0 +1,247 @@
+// MGC + idle pumps under realistic startup times — three scenarios that
+// pin down WHERE the live deadlock is happening when PS sends 100% but
+// pumps "show on" without adopting the control value.
+//
+// All three scenarios start with idle pumps (NOT pre-started) and use
+// non-zero state.time values so startup is observable. Each scenario
+// prints the per-pump snapshot at the end. The asserts state what we
+// EXPECT to happen — failures point at the exact codepath that breaks.
+//
+// Compare to demand-cycle-walkthrough.integration.test.js which
+// pre-starts every pump to 'operational' and therefore CANNOT exercise
+// the idle-during-rapid-retarget paths described here.
+
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const MachineGroup = require('../../src/specificClass');
+const Machine = require('../../../rotatingMachine/src/specificClass');
+
+const HEAD_MBAR_UP = 0;
+const HEAD_MBAR_DOWN = 1100;
+const N_PUMPS = 3;
+
+const LOG_DEBUG = process.env.LOG_DEBUG === '1';
+const logCfg = { enabled: LOG_DEBUG, logLevel: LOG_DEBUG ? 'debug' : 'error' };
+
+// Production-realistic-but-shrunk: starting=1s, warmingup=2s. Total
+// startup ~3s. Long enough for rapid retargeting (every 200ms) to land
+// 10+ extra calls during the transient, short enough to keep the test
+// well under 30s.
+const stateConfig = {
+  general: { logging: logCfg },
+  state: { current: 'idle' },
+  movement: { mode: 'staticspeed', speed: 200, maxSpeed: 200, interval: 50 },
+  time: { starting: 1, warmingup: 2, stopping: 1, coolingdown: 2 },
+};
+
+function machineConfig(id) {
+  return {
+    general: { logging: logCfg, name: id, id, unit: 'm3/h' },
+    functionality: { softwareType: 'machine', role: 'rotationaldevicecontroller' },
+    asset: { category: 'pump', type: 'centrifugal', model: 'hidrostal-H05K-S03R', supplier: 'hidrostal' },
+    mode: {
+      current: 'auto',
+      allowedActions: { auto: ['execsequence', 'execmovement', 'flowmovement', 'statuscheck'] },
+      allowedSources: { auto: ['parent', 'GUI'] },
+    },
+    sequences: {
+      startup:        ['starting', 'warmingup', 'operational'],
+      shutdown:       ['stopping', 'coolingdown', 'idle'],
+      emergencystop:  ['emergencystop', 'off'],
+    },
+  };
+}
+
+function groupConfig() {
+  return {
+    general: { logging: logCfg, name: 'mgc', id: 'mgc' },
+    functionality: { softwareType: 'machinegroup', role: 'groupcontroller', positionVsParent: 'atEquipment' },
+    scaling: { current: 'normalized' },
+    mode:    { current: 'optimalcontrol' },
+  };
+}
+
+function buildGroup({ withPressure = true } = {}) {
+  const mgc = new MachineGroup(groupConfig());
+  const ids = Array.from({ length: N_PUMPS }, (_, i) => `pump_${String.fromCharCode(97 + i)}`);
+  const pumps = ids.map(id => new Machine(machineConfig(id), stateConfig));
+  for (const m of pumps) {
+    if (withPressure) {
+      m.updateMeasuredPressure(HEAD_MBAR_UP, 'upstream', {
+        timestamp: Date.now(), unit: 'mbar', childName: 'up', childId: `up-${m.config.general.id}` });
+      m.updateMeasuredPressure(HEAD_MBAR_DOWN, 'downstream', {
+        timestamp: Date.now(), unit: 'mbar', childName: 'dn', childId: `dn-${m.config.general.id}` });
+    }
+    mgc.childRegistrationUtils.registerChild(m, 'downstream');
+  }
+  mgc.calcAbsoluteTotals();
+  mgc.calcDynamicTotals();
+  return { mgc, pumps };
+}
+
+const sleep = (ms) => new Promise(r => setTimeout(r, ms));
+
+const NON_RUNNING = new Set(['idle', 'off', 'stopping', 'coolingdown', 'emergencystop']);
+function snapshot(pump) {
+  const state = pump.state.getCurrentState();
+  const ctrl  = Number(pump.state.getCurrentPosition?.() ?? 0);
+  const running = !NON_RUNNING.has(state);
+  const flow  = running ? Number(pump.predictFlow?.outputY  ?? 0) * 3600 : 0;
+  const power = running ? Number(pump.predictPower?.outputY ?? 0) / 1000 : 0;
+  return { state, ctrl, flow, power, delayedMove: pump.state.delayedMove };
+}
+
+function printSnapshots(label, pumps) {
+  console.log(`\n  --- ${label} ---`);
+  console.log('  ' + ['id'.padEnd(8), 'state'.padEnd(14), 'ctrl%'.padStart(6), 'Q m³/h'.padStart(8), 'kW'.padStart(6), 'delayedMove'.padStart(12)].join(' '));
+  console.log('  ' + '-'.repeat(60));
+  for (const p of pumps) {
+    const s = snapshot(p);
+    console.log('  ' + [
+      p.config.general.id.padEnd(8),
+      s.state.padEnd(14),
+      s.ctrl.toFixed(1).padStart(6),
+      s.flow.toFixed(1).padStart(8),
+      s.power.toFixed(1).padStart(6),
+      String(s.delayedMove).padStart(12),
+    ].join(' '));
+  }
+}
+
+function expectAllRunningAt100(pumps, label) {
+  // After settle every pump should be operational with high ctrl% and
+  // measurable flow. "high" is conservative — at 100% normalized demand,
+  // 3-pump split puts each pump near 100% ctrl. Allow >70% as the floor
+  // (accommodates BEP-Gravitation's slight asymmetry at the curve edges).
+  for (const p of pumps) {
+    const s = snapshot(p);
+    assert.equal(s.state, 'operational',
+      `${label}: pump ${p.config.general.id} expected operational, got '${s.state}' (ctrl=${s.ctrl.toFixed(1)}, delayedMove=${s.delayedMove})`);
+    assert.ok(s.ctrl > 70,
+      `${label}: pump ${p.config.general.id} expected ctrl% > 70 at 100% demand, got ${s.ctrl.toFixed(2)} (state=${s.state}, delayedMove=${s.delayedMove})`);
+    assert.ok(s.flow > 100,
+      `${label}: pump ${p.config.general.id} expected flow > 100 m³/h, got ${s.flow.toFixed(2)} (state=${s.state}, ctrl=${s.ctrl.toFixed(1)})`);
+  }
+}
+
+// ---------------------------------------------------------------------------
+test('Scenario 1 — single-shot 100% demand to idle pumps', async () => {
+  // Hypothesis A: a SINGLE handleInput call to MGC with all pumps idle is
+  // enough to surface the bug. If pumps end up at 100% ctrl, the bug is
+  // elsewhere (rapid retargeting OR pressure plumbing). If pumps stay at
+  // 0%, the dispatch loop itself doesn't follow through on
+  // execsequence-startup → flowmovement.
+
+  const { mgc, pumps } = buildGroup();
+  console.log(`\n[Scenario 1] head=${HEAD_MBAR_DOWN} mbar, time.starting=${stateConfig.time.starting}s, time.warmingup=${stateConfig.time.warmingup}s`);
+  printSnapshots('before handleInput', pumps);
+
+  await mgc.handleInput('parent', 100);
+  printSnapshots('immediately after handleInput returns', pumps);
+
+  // Wait for full startup (3s) + movement (~0.5s) + slack
+  await sleep(6000);
+  printSnapshots('after 6s settle', pumps);
+
+  expectAllRunningAt100(pumps, 'Scenario 1');
+});
+
+// ---------------------------------------------------------------------------
+test('Scenario 2 — rapid 100% retargeting during startup window', async () => {
+  // Hypothesis B: PS fires _applyMachineGroupLevelControl on every level
+  // tick (every few hundred ms). While pumps are in 'starting' /
+  // 'warmingup', MGC's optimalControl loop snapshots them, hits NONE of
+  // its three branches (idle / operational / flow<=0), and dispatches
+  // nothing. The only reason pumps eventually move is the FIRST call's
+  // queued `await flowmovement` after `await execsequence startup` —
+  // unless a subsequent call's abortActiveMovements aborts that move
+  // mid-flight, parking it in 'accelerating'/'decelerating'.
+
+  const { mgc, pumps } = buildGroup();
+  console.log(`\n[Scenario 2] firing mgc.handleInput('parent', 100) every 200ms for 5s`);
+  printSnapshots('before any handleInput', pumps);
+
+  // First call (kicks off startup); not awaited so retargets can layer on.
+  mgc.handleInput('parent', 100).catch(e => console.log(`first call rejected: ${e.message}`));
+
+  // Spam additional retargets every 200ms for 5s — covers the 3s startup
+  // window with 25 extra retargeting calls.
+  const interval = setInterval(() => {
+    mgc.handleInput('parent', 100).catch(e => console.log(`retarget rejected: ${e.message}`));
+  }, 200);
+  await sleep(5000);
+  clearInterval(interval);
+
+  printSnapshots('right after retarget barrage stops', pumps);
+
+  // Drain: let any pending moves finish and let the FSM settle.
+  await sleep(3000);
+  printSnapshots('after 3s drain', pumps);
+
+  expectAllRunningAt100(pumps, 'Scenario 2');
+});
+
+// ---------------------------------------------------------------------------
+test('Scenario 3 — pumps with NO pressure measurements injected', async () => {
+  // Hypothesis C: in production, MGC may receive a demand BEFORE the
+  // first pressure measurement has propagated. Without head, the curve's
+  // operating point is at fDimension=defaults, and currentFxyYMin/Max
+  // may not correspond to a usable envelope. If MGC's distributor then
+  // hands every pump flow≤0, the dispatch loop falls into the 'flow<=0
+  // → shutdown' branch and pumps go straight to idle.
+
+  const { mgc, pumps } = buildGroup({ withPressure: false });
+  const sample = pumps[0].groupPredictFlow ?? pumps[0].predictFlow;
+  const minQ = sample.currentFxyYMin * 3600;
+  const maxQ = sample.currentFxyYMax * 3600;
+  const dyn = mgc.calcDynamicTotals();
+  console.log(`\n[Scenario 3] no pressure injected. per-pump curve envelope: ${minQ.toFixed(1)} .. ${maxQ.toFixed(1)} m³/h, station: ${(dyn.flow.min*3600).toFixed(1)} .. ${(dyn.flow.max*3600).toFixed(1)} m³/h`);
+  printSnapshots('before handleInput', pumps);
+
+  await mgc.handleInput('parent', 100);
+  await sleep(6000);
+  printSnapshots('after 6s settle (no pressure)', pumps);
+
+  // We don't assert success here — this scenario is exploratory. Just
+  // log what happens. If pumps DO ramp despite no pressure, MGC is
+  // resilient. If they stay idle, that's a meaningful failure mode for
+  // the live system because a redeploy may rebuild the world before
+  // sensors republish.
+  console.log('  (Scenario 3 is exploratory — no asserts; review the snapshot above.)');
+});
+
+// ---------------------------------------------------------------------------
+test('Scenario 4 — varying demand during startup (combo flips)', async () => {
+  // Hypothesis D: in production the demand is NOT constant — as basin
+  // level rises, percControl ramps from startLevel→maxLevel over the
+  // basin model. Demand can flip between 1-pump / 2-pump / 3-pump
+  // combinations every PS tick. Each flip in optimalControl tells some
+  // pumps to start, others to shutdown, others nothing. If a pump that
+  // was just told "startup" is told "shutdown" 1s later (still in
+  // 'starting' state — neither idle nor operational), nothing happens
+  // for that pump in this snapshot. The execsequence shutdown branch
+  // requires state to be operational/accelerating/decelerating — a
+  // 'starting'/'warmingup' pump is silently passed over for shutdown
+  // too. The pump then proceeds to operational AND obeys its queued
+  // flowmovement, even though MGC's intent has since changed.
+
+  const { mgc, pumps } = buildGroup();
+  const sequence = [25, 75, 50, 100, 30, 90, 60, 100];
+  console.log(`\n[Scenario 4] varying demand sequence: ${sequence.join(' → ')} (each held 400ms)`);
+  printSnapshots('before any handleInput', pumps);
+
+  for (const pct of sequence) {
+    console.log(`  → demand ${pct}%`);
+    mgc.handleInput('parent', pct).catch(e => console.log(`call ${pct}% rejected: ${e.message}`));
+    await sleep(400);
+  }
+
+  printSnapshots('right after sequence ends', pumps);
+
+  // Final demand was 100% — drain and verify pumps converged.
+  await sleep(4000);
+  printSnapshots('after 4s drain (demand was last set to 100%)', pumps);
+
+  expectAllRunningAt100(pumps, 'Scenario 4');
+});
diff --git a/test/integration/optimizer-combination-choice.integration.test.js b/test/integration/optimizer-combination-choice.integration.test.js
new file mode 100644
index 0000000..3ad4e4d
--- /dev/null
+++ b/test/integration/optimizer-combination-choice.integration.test.js
@@ -0,0 +1,169 @@
+// MGC optimizer combination choice — given a known operating point and
+// 3 identical pumps, walk demand from below per-pump min through to
+// full station capacity and assert the optimizer always returns a
+// combination whose per-pump split lies within each pump's curve.
+//
+// This is a regression test. Earlier traces showed per-pump flow values
+// that looked impossible (78 m³/h while we believed min was ~99). The
+// real explanation: the curve's currentFxyYMin shifts with head — at
+// 1652 mbar the per-pump min IS 49 m³/h. This test pins the optimizer's
+// behaviour at a single deterministic head so the asserted ranges are
+// stable.
+
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const MachineGroup = require('../../src/specificClass');
+const Machine      = require('../../../rotatingMachine/src/specificClass');
+
+const HEAD_MBAR_DOWN = 1100;
+const HEAD_MBAR_UP   = 0;
+
+const stateConfig = {
+  time: { starting: 0, warmingup: 0, stopping: 0, coolingdown: 0 },
+  movement: { speed: 1200, mode: 'staticspeed', maxSpeed: 1800 },
+};
+
+function machineConfig(id) {
+  return {
+    general: { logging: { enabled: false, logLevel: 'error' }, name: id, id, unit: 'm3/h' },
+    functionality: { softwareType: 'machine', role: 'rotationaldevicecontroller' },
+    asset: { category: 'pump', type: 'centrifugal', model: 'hidrostal-H05K-S03R', supplier: 'hidrostal' },
+    mode: {
+      current: 'auto',
+      allowedActions: { auto: ['execsequence', 'execmovement', 'flowmovement', 'statuscheck'] },
+      allowedSources: { auto: ['parent', 'GUI'] },
+    },
+    sequences: {
+      startup: ['starting', 'warmingup', 'operational'],
+      shutdown: ['stopping', 'coolingdown', 'idle'],
+      emergencystop: ['emergencystop', 'off'],
+    },
+  };
+}
+
+function groupConfig() {
+  return {
+    general: { logging: { enabled: false, logLevel: 'error' }, name: 'mgc', id: 'mgc' },
+    functionality: { softwareType: 'machinegroup', role: 'groupcontroller', positionVsParent: 'atEquipment' },
+    scaling: { current: 'absolute' },     // talk to MGC in m³/h directly
+    mode: { current: 'optimalcontrol' },
+  };
+}
+
+function buildGroup() {
+  const mgc = new MachineGroup(groupConfig());
+  const ids = ['pump_a', 'pump_b', 'pump_c'];
+  const pumps = ids.map(id => new Machine(machineConfig(id), stateConfig));
+  for (const m of pumps) {
+    // Inject deterministic pressures so every pump sees the same head.
+    m.updateMeasuredPressure(HEAD_MBAR_UP,   'upstream',
+      { timestamp: Date.now(), unit: 'mbar', childName: 'up', childId: `up-${m.config.general.id}` });
+    m.updateMeasuredPressure(HEAD_MBAR_DOWN, 'downstream',
+      { timestamp: Date.now(), unit: 'mbar', childName: 'dn', childId: `dn-${m.config.general.id}` });
+    mgc.childRegistrationUtils.registerChild(m, 'downstream');
+  }
+  mgc.calcAbsoluteTotals();
+  mgc.calcDynamicTotals();
+  return { mgc, pumps };
+}
+
+test('optimizer always returns a physically valid split (head=1100 mbar)', () => {
+  // The core invariant: whatever combination the optimizer picks, every
+  // per-pump assignment must lie inside that pump's curve envelope at
+  // the current operating point, and the total must equal the demand.
+  // This is what makes a combo "physically valid". The optimizer is
+  // free to pick fewer or more pumps based on efficiency — that is NOT
+  // a violation.
+
+  const { mgc, pumps } = buildGroup();
+  const sample = pumps[0].groupPredictFlow ?? pumps[0].predictFlow;
+  const minPerPump = sample.currentFxyYMin * 3600;
+  const maxPerPump = sample.currentFxyYMax * 3600;
+  // Guard against a curve-data change silently invalidating the asserts.
+  assert.ok(minPerPump > 80 && minPerPump < 100,
+    `unexpected curve min ${minPerPump} at 1100 mbar`);
+  assert.ok(maxPerPump > 220 && maxPerPump < 230,
+    `unexpected curve max ${maxPerPump} at 1100 mbar`);
+
+  const stationMax = maxPerPump * pumps.length;     // ≈ 681
+  // Note: we deliberately stay 1 m³/h short of stationMax to avoid a
+  // floating-point edge where validPumpCombinations rejects an exact
+  // boundary demand. Real demand is never exactly station max anyway.
+  const demands = [0, 50, minPerPump - 5, minPerPump, 150, 200, 230, 250, 300, 400, 500, 600, stationMax - 1];
+
+  const rows = [];
+  for (const Qd_m3h of demands) {
+    const Qd_m3s = Qd_m3h / 3600;
+    const combos = mgc.validPumpCombinations(mgc.machines, Qd_m3s, Infinity);
+    if (combos.length === 0) {
+      rows.push({ Qd_m3h, picked: null, perPump: [], total: 0 });
+      // The validity rule rejects a combo when Qd is outside its
+      // [sum(min), sum(max)] envelope. With only 3 identical pumps at
+      // this head, that means Qd < minPerPump (no combo's min envelope
+      // contains it) or Qd > stationMax. Strict zero is also rejected.
+      assert.ok(Qd_m3h <= 0 || Qd_m3h < minPerPump,
+        `unexpected: no valid combo for Qd=${Qd_m3h} (per-pump ${minPerPump.toFixed(2)}..${maxPerPump.toFixed(2)}, station max ${stationMax.toFixed(2)})`);
+      continue;
+    }
+
+    const best = mgc.calcBestCombinationBEPGravitation(combos, Qd_m3s, 'BEP-Gravitation-Directional');
+    assert.ok(best.bestCombination, `no bestCombination for Qd=${Qd_m3h}`);
+    const split = best.bestCombination.map(e => e.flow * 3600);
+    const total = split.reduce((s, x) => s + x, 0);
+    rows.push({ Qd_m3h, picked: best.bestCombination.length, perPump: split, total });
+
+    // Each per-pump split must lie in [minPerPump, maxPerPump].
+    for (const f of split) {
+      assert.ok(f >= minPerPump - 1e-3,
+        `Qd=${Qd_m3h}: per-pump ${f.toFixed(2)} below min ${minPerPump.toFixed(2)}`);
+      assert.ok(f <= maxPerPump + 1e-3,
+        `Qd=${Qd_m3h}: per-pump ${f.toFixed(2)} above max ${maxPerPump.toFixed(2)}`);
+    }
+    assert.ok(Math.abs(total - Qd_m3h) < Math.max(1, Qd_m3h * 0.01),
+      `Qd=${Qd_m3h}: total ${total.toFixed(2)} ≠ demand`);
+  }
+
+  // Print the chosen combinations for inspection.
+  console.log(`\nHead = ${HEAD_MBAR_DOWN - HEAD_MBAR_UP} mbar`);
+  console.log(`Per-pump curve: min=${minPerPump.toFixed(2)} m³/h, max=${maxPerPump.toFixed(2)} m³/h`);
+  console.log(`Station max (3 pumps × max): ${stationMax.toFixed(2)} m³/h\n`);
+  console.log('  demand  pumps  per-pump split');
+  console.log('  ──────  ─────  ─────────────────────────────');
+  for (const r of rows) {
+    if (r.picked == null) {
+      console.log(`  ${r.Qd_m3h.toFixed(1).padStart(6)}  none  no valid combo`);
+    } else {
+      console.log(`  ${r.Qd_m3h.toFixed(1).padStart(6)}  ${r.picked}      [${r.perPump.map(f => f.toFixed(1)).join(', ')}]  total=${r.total.toFixed(1)}`);
+    }
+  }
+});
+
+test('feasibility floor and ceiling: only 1-pump combo serves demand below 2×min', () => {
+  // The optimizer is allowed to pick larger combos for efficiency, but
+  // it CANNOT pick a combo whose [sum(min), sum(max)] doesn't contain
+  // the demand. This pins down the floor / ceiling rules.
+
+  const { mgc, pumps } = buildGroup();
+  const sample = pumps[0].groupPredictFlow ?? pumps[0].predictFlow;
+  const minPerPump = sample.currentFxyYMin * 3600;
+  const maxPerPump = sample.currentFxyYMax * 3600;
+
+  // Demand below per-pump min → no combo at all. (sum(min) ≥ minPerPump
+  // for every non-empty combo, and Qd < sum(min) ⇒ rejected.)
+  let combos = mgc.validPumpCombinations(mgc.machines, (minPerPump - 5) / 3600, Infinity);
+  assert.equal(combos.length, 0, `demand below per-pump min should yield 0 valid combos, got ${combos.length}`);
+
+  // Demand within [minPerPump, 2*minPerPump): only 1-pump combos pass.
+  // (2-pump min envelope = 2×minPerPump > Qd.)
+  const Qd1 = (minPerPump + 5) / 3600;
+  combos = mgc.validPumpCombinations(mgc.machines, Qd1, Infinity);
+  for (const c of combos) {
+    assert.equal(c.length, 1,
+      `demand ${minPerPump+5} m³/h: only 1-pump combos should be valid (got ${c.length}-pump)`);
+  }
+
+  // Demand above station max → no valid combo.
+  combos = mgc.validPumpCombinations(mgc.machines, (maxPerPump * 3 + 50) / 3600, Infinity);
+  assert.equal(combos.length, 0, `demand above station max should yield 0 valid combos`);
+});