diff --git a/frontend/src/simulation/parts/BasicParts.ts b/frontend/src/simulation/parts/BasicParts.ts
index 76428465..3d428ea7 100644
--- a/frontend/src/simulation/parts/BasicParts.ts
+++ b/frontend/src/simulation/parts/BasicParts.ts
@@ -1,5 +1,6 @@
 import { PartSimulationRegistry } from './PartSimulationRegistry';
 import { useElectricalStore } from '../../store/useElectricalStore';
+import { useSimulatorStore } from '../../store/useSimulatorStore';
 import { emitPropertyChange } from './partUtils';
 
 /**
@@ -171,6 +172,14 @@ const LED_BURNOUT_A = 0.1;
 /** Surface a circuit fault for an LED — console + a UI event the toolbar shows. */
 function reportLedFault(componentId: string, kind: string, message: string): void {
   console.warn(`[led] ${componentId}: ${message}`);
+  // Mark it destroyed in the shared burnt set (P4): the canvas renders it
+  // charred + a smoke badge, and the solver opens it — same treatment as a
+  // burnt resistor/capacitor. (The LED also goes dark via its own update.)
+  try {
+    useSimulatorStore.getState().markComponentBurnt?.(componentId);
+  } catch {
+    /* store unavailable (test env) — ignore */
+  }
   if (typeof window !== 'undefined' && typeof window.dispatchEvent === 'function') {
     try {
       window.dispatchEvent(
diff --git a/frontend/src/simulation/spice/CircuitSimulationService.ts b/frontend/src/simulation/spice/CircuitSimulationService.ts
index 2972e07c..f388937b 100644
--- a/frontend/src/simulation/spice/CircuitSimulationService.ts
+++ b/frontend/src/simulation/spice/CircuitSimulationService.ts
@@ -40,6 +40,9 @@ export interface SimulatorStorePort {
       end: { componentId: string; pinName: string };
     }>;
     boards: Array<{ id: string; boardKind: string; pinStates?: Record<string, unknown> }>;
+    /** Components destroyed at runtime (P4) — excluded from the netlist so a
+     *  burnt part actually goes open. Optional for non-store ports. */
+    burntComponents?: Set<string>;
   };
   subscribe(listener: (state: unknown, prev: unknown) => void): () => void;
 }
@@ -279,8 +282,14 @@ export class CircuitSimulationService {
 
   private async runSolve(): Promise<void> {
     const state = this.simStore.getState();
+    // P4: a runtime-destroyed part is excluded from the netlist so it actually
+    // goes open — its current stops and anything it fed loses power (cascading
+    // failure), the way real hardware behaves once a component burns out.
+    const burnt = state.burntComponents;
+    const liveComponents =
+      burnt && burnt.size > 0 ? state.components.filter((c) => !burnt.has(c.id)) : state.components;
     const snap = {
-      components: state.components,
+      components: liveComponents,
       wires: state.wires,
       boards: state.boards.map((b) => ({
         id: b.id,