diff --git a/frontend/src/simulation/AVRSimulator.ts b/frontend/src/simulation/AVRSimulator.ts
index d08c39c4..97c22084 100644
--- a/frontend/src/simulation/AVRSimulator.ts
+++ b/frontend/src/simulation/AVRSimulator.ts
@@ -295,15 +295,6 @@ const MEGA_PORT_CONFIGS = [
 ];
 
 export class AVRSimulator {
-  // Digital input pins are driven from the SPICE solve
-  // (connectDigitalInputsToMcu) for nets backed by a real source/element, so
-  // `digitalRead()` reflects the real wiring (a pin wired to 5V reads HIGH, a
-  // button to 5V reads HIGH when pressed) instead of a hardcoded part seed.
-  // The connector skips floating nets, so event-driven parts with no SPICE
-  // model (rotary encoder, keypad, dialer, dip-switch, stepper) keep driving
-  // their pins via the part layer. Input-control parts (button / slide-switch)
-  // check this flag and skip their direct seed — see BasicParts.spiceDriven().
-  readonly spiceDrivenInputs = true;
   private cpu: CPU | null = null;
   /** Peripherals kept alive by reference so GC doesn't collect their CPU hooks */
   private peripherals: unknown[] = [];
diff --git a/frontend/src/simulation/RP2040Simulator.ts b/frontend/src/simulation/RP2040Simulator.ts
index dd84a0c2..8a666b84 100644
--- a/frontend/src/simulation/RP2040Simulator.ts
+++ b/frontend/src/simulation/RP2040Simulator.ts
@@ -145,12 +145,6 @@ export class IdleSpinDetector {
 export type RP2040I2CDevice = I2CDevice;
 
 export class RP2040Simulator {
-  // Digital inputs are driven from the SPICE solve (connectDigitalInputsToMcu)
-  // for source-backed nets, so digitalRead reflects real wiring (a GP pin wired
-  // to a rail / button reads the right level). Floating nets are left to the
-  // part layer, so event-driven parts (encoder/keypad/…) keep working. Mirrors
-  // the AVR fix; the connector + sourcedNets gating are board-agnostic.
-  readonly spiceDrivenInputs = true;
   private rp2040: RP2040 | null = null;
   private running = false;
   private animationFrame: number | null = null;
diff --git a/frontend/src/simulation/spice/CircuitSimulationService.ts b/frontend/src/simulation/spice/CircuitSimulationService.ts
index 3988e51b..1fb3e8d7 100644
--- a/frontend/src/simulation/spice/CircuitSimulationService.ts
+++ b/frontend/src/simulation/spice/CircuitSimulationService.ts
@@ -67,9 +67,6 @@ export interface ElectricalSnapshot {
   timeWaveforms?: TimeWaveforms;
   /** Convergence warnings from the solver. */
   warnings: string[];
-  /** Nets backed by a real source/element (see NetlistBuilder). Gates which
-   *  MCU input pins connectDigitalInputsToMcu may drive from the solve. */
-  sourcedNets: Set<string>;
 }
 
 /** What the service needs from the scheduler. */
@@ -133,7 +130,6 @@ export class CircuitSimulationService {
     nets: string[];
     voltageSources: string[];
     analysisKind: 'op' | 'tran' | 'ac';
-    sourcedNets: Set<string>;
   } | null = null;
 
   /** Set by `stop()`. Once true, `tick()` and `handleMcuEdge()`
@@ -306,7 +302,7 @@ export class CircuitSimulationService {
       })),
     };
     const input = buildInputFromStore(snap as Parameters<typeof buildInputFromStore>[0]);
-    const { netlist, pinNetMap, nets, voltageSources, sourcedNets } = buildNetlist(input);
+    const { netlist, pinNetMap, nets, voltageSources } = buildNetlist(input);
 
     // Tell the scheduler exactly which vectors we want — every net
     // voltage + every branch current.
@@ -330,7 +326,6 @@ export class CircuitSimulationService {
       nets,
       voltageSources,
       analysisKind: input.analysis.kind,
-      sourcedNets,
     };
     this.publishFromLastResult();
   }
@@ -385,7 +380,6 @@ export class CircuitSimulationService {
       analysisMode: ctx.analysisKind,
       timeWaveforms,
       warnings: result.warnings,
-      sourcedNets: ctx.sourcedNets,
     });
   }
 
diff --git a/frontend/src/simulation/spice/NetlistBuilder.ts b/frontend/src/simulation/spice/NetlistBuilder.ts
index 3e632c0b..be20a913 100644
--- a/frontend/src/simulation/spice/NetlistBuilder.ts
+++ b/frontend/src/simulation/spice/NetlistBuilder.ts
@@ -67,18 +67,6 @@ export interface BuildNetlistResult {
    * request branch currents (`i(v_<name>)`).
    */
   voltageSources: string[];
-  /**
-   * Nets that are backed by a real electrical source/element — a power rail
-   * ('0' / 'vcc_rail'), a board GPIO V-source, an internal pull resistor, or
-   * any net a componentToSpice mapper emitted a card for (resistor, button
-   * switch, divider, etc.). Excludes purely-floating nets (which only get the
-   * step-7 auto-pull-down). `connectDigitalInputsToMcu` drives an MCU input pin
-   * from the solve ONLY when its net is in here, so event-driven parts with no
-   * SPICE model (rotary encoder, keypad, dialer, dip-switch, stepper) keep
-   * driving their own pins via the part layer instead of being forced LOW by a
-   * floating-net read.
-   */
-  sourcedNets: Set<string>;
 }
 
 export function buildNetlist(input: BuildNetlistInput): BuildNetlistResult {
@@ -150,11 +138,6 @@ export function buildNetlist(input: BuildNetlistInput): BuildNetlistResult {
   const cards: string[] = [];
   const modelLines = new Set<string>();
   const dominantVcc = boards[0]?.vcc ?? 5;
-  // Nets backed by a real source/element (see BuildNetlistResult.sourcedNets).
-  // Rails are always sourced; component + GPIO-source + pull nets are added
-  // below. Deliberately NOT populated from the step-7 auto-pull-down cards,
-  // since those mark FLOATING nets.
-  const sourcedNets = new Set<string>(['0', 'vcc_rail']);
 
   for (const comp of components) {
     const localLookup = (pinName: string) => netLookup(comp.id, pinName);
@@ -162,11 +145,6 @@ export function buildNetlist(input: BuildNetlistInput): BuildNetlistResult {
     if (!emission) continue;
     cards.push(...emission.cards);
     for (const m of emission.modelsUsed) modelLines.add(m);
-    // Every net this component connects to now has a real SPICE element on it.
-    for (const pinName of pinsReferencedByWires(comp.id, wires)) {
-      const n = netLookup(comp.id, pinName);
-      if (n) sourcedNets.add(n);
-    }
   }
 
   // ── 5. Board GPIO sources ─────────────────────────────────────────────────
@@ -196,7 +174,6 @@ export function buildNetlist(input: BuildNetlistInput): BuildNetlistResult {
           cards.push(
             `R_pull_${sanitizeSpiceId(board.id)}_${sanitizeSpiceId(pinName)} ${net} ${rail} 45000`,
           );
-          sourcedNets.add(net); // weak pull to a rail → determinate idle level
         }
         continue;
       }
@@ -204,7 +181,6 @@ export function buildNetlist(input: BuildNetlistInput): BuildNetlistResult {
       if (net === '0' || net === 'vcc_rail') continue; // already served
       const v = state.type === 'digital' ? state.v : state.duty * board.vcc;
       cards.push(`V_${sanitizeSpiceId(board.id)}_${sanitizeSpiceId(pinName)} ${net} 0 DC ${v}`);
-      sourcedNets.add(net); // board GPIO V-source drives this net (e.g. cross-board input)
     }
   }
 
@@ -227,8 +203,6 @@ export function buildNetlist(input: BuildNetlistInput): BuildNetlistResult {
     const b = netLookup(w.end.componentId, w.end.pinName);
     if (!a || !b) continue;
     cards.push(`R_wire_${w.id} ${a} ${b} ${ohms}`);
-    sourcedNets.add(a);
-    sourcedNets.add(b);
   }
 
   // ── 7. Auto pull-downs for floating nets ─────────────────────────────────
@@ -305,7 +279,6 @@ export function buildNetlist(input: BuildNetlistInput): BuildNetlistResult {
     pinNetMap,
     nets,
     voltageSources,
-    sourcedNets,
   };
 }
 
diff --git a/frontend/src/simulation/spice/connectDigitalInputsToMcu.ts b/frontend/src/simulation/spice/connectDigitalInputsToMcu.ts
index 843a02e2..fb2effee 100644
--- a/frontend/src/simulation/spice/connectDigitalInputsToMcu.ts
+++ b/frontend/src/simulation/spice/connectDigitalInputsToMcu.ts
@@ -21,8 +21,6 @@
  */
 import { useSimulatorStore, getBoardSimulator, getBoardPinManager } from '../../store/useSimulatorStore';
 import { useElectricalStore } from '../../store/useElectricalStore';
-import { isStm32BoardKind } from '../../types/board';
-import { stm32PinNameToLinear } from '../Stm32Bridge';
 
 // 3.3 V LVCMOS thresholds with a hysteresis band so a node hovering near the
 // midpoint doesn't chatter. A pulled-up idle input sits at ~3.3 V and a
@@ -45,7 +43,7 @@ export function connectDigitalInputsToMcu(): () => void {
   const lastLevel = new Map<string, boolean>();
 
   function injectDigitalInputs() {
-    const { nodeVoltages, pinNetMap, sourcedNets } = useElectricalStore.getState();
+    const { nodeVoltages, pinNetMap } = useElectricalStore.getState();
     const { boards } = useSimulatorStore.getState();
     for (const board of boards) {
       const sim = getBoardSimulator(board.id) as
@@ -55,23 +53,11 @@ export function connectDigitalInputsToMcu(): () => void {
       const pm = getBoardPinManager(board.id);
       const driven = pm ? pm.getOutputPins() : new Set<number>();
       const prefix = `${board.id}:`;
-      // STM32 names pins PA0/PC13/… and its PinManager + setPinState key on the
-      // linear pin (port*16+pin); every other board uses plain GPIO numbers.
-      const isStm32 = isStm32BoardKind(board.boardKind);
       for (const [key, net] of pinNetMap) {
         if (!key.startsWith(prefix)) continue;
-        const pinName = key.slice(prefix.length);
-        const gpio = isStm32 ? stm32PinNameToLinear(pinName) : gpioFromPinName(pinName);
+        const gpio = gpioFromPinName(key.slice(prefix.length));
         if (gpio < 0) continue;
         if (driven.has(gpio)) continue; // the MCU drives this pin (digitalWrite)
-        // Only drive pins whose net is backed by a real source/element (rail,
-        // pull, button switch, divider, cross-board output, …). A net that is
-        // only floating (an event-driven part like a rotary encoder / keypad
-        // that has no SPICE model) is left to the part layer, which seeds the
-        // pin directly — otherwise its ~0 V floating read would force it LOW
-        // and fight the part. This is what makes it safe to enable
-        // spiceDrivenInputs on the AVR (which has many such part-driven pins).
-        if (!sourcedNets.has(net)) continue;
         const v = nodeVoltages[net];
         if (v == null) continue;
         const stateKey = `${board.id}:${gpio}`;
diff --git a/frontend/src/simulation/spice/start.ts b/frontend/src/simulation/spice/start.ts
index f583bc55..0979c4ad 100644
--- a/frontend/src/simulation/spice/start.ts
+++ b/frontend/src/simulation/spice/start.ts
@@ -50,7 +50,6 @@ function createElectricalStorePort(): ElectricalStorePort {
         error: snapshot.warnings[0] ?? null,
         lastSolveMs: 0,
         submittedNetlist: '',
-        sourcedNets: snapshot.sourcedNets,
       });
     },
   };
diff --git a/frontend/src/store/useElectricalStore.ts b/frontend/src/store/useElectricalStore.ts
index d2a7a46b..b8e47f6b 100644
--- a/frontend/src/store/useElectricalStore.ts
+++ b/frontend/src/store/useElectricalStore.ts
@@ -25,10 +25,6 @@ export interface ElectricalSnapshot {
   error: string | null;
   lastSolveMs: number;
   submittedNetlist: string;
-  /** Nets backed by a real source/element (rail, GPIO V-source, pull, or any
-   *  component card). connectDigitalInputsToMcu only drives MCU input pins
-   *  whose net is here, so floating event-part pins aren't forced LOW. */
-  sourcedNets: Set<string>;
 }
 
 interface ElectricalState extends ElectricalSnapshot {
@@ -55,7 +51,6 @@ const EMPTY: ElectricalSnapshot = {
   error: null,
   lastSolveMs: 0,
   submittedNetlist: '',
-  sourcedNets: new Set(),
 };
 
 export const useElectricalStore = create<ElectricalState>((set) => ({
diff --git a/frontend/src/store/useSimulatorStore.ts b/frontend/src/store/useSimulatorStore.ts
index 3d9be4d1..ff31dba4 100644
--- a/frontend/src/store/useSimulatorStore.ts
+++ b/frontend/src/store/useSimulatorStore.ts
@@ -600,12 +600,6 @@ function makePinPullHandler(boardId: string) {
 // minus the ESP32-only WiFi / proxy-resync machinery. ──────────────────────
 class Stm32BridgeShim {
   pinManager: PinManager;
-  // Digital inputs are driven from the SPICE solve (connectDigitalInputsToMcu)
-  // for source-backed nets — digitalRead reflects the real wiring instead of a
-  // part seed. The connector maps STM32 pin names (PA0, PC13) to the linear pin
-  // setPinState expects via stm32PinNameToLinear. Floating nets stay with the
-  // part layer. Mirrors the AVR / RP2040 fix.
-  readonly spiceDrivenInputs = true;
   onSerialData: ((ch: string) => void) | null = null;
   onPinChangeWithTime: ((pin: number, state: boolean, timeMs: number) => void) | null = null;
   onBaudRateChange: ((baud: number) => void) | null = null;