diff --git a/packages/durabletask-js/src/utils/pb-helper.util.ts b/packages/durabletask-js/src/utils/pb-helper.util.ts
index dd03077..100f0b2 100644
--- a/packages/durabletask-js/src/utils/pb-helper.util.ts
+++ b/packages/durabletask-js/src/utils/pb-helper.util.ts
@@ -236,6 +236,22 @@ export function newEventRaisedEvent(name: string, encodedInput?: string): pb.His
   return event;
 }
 
+export function newEventSentEvent(eventId: number, instanceId: string, name: string, encodedInput?: string): pb.HistoryEvent {
+  const ts = new Timestamp();
+
+  const eventSent = new pb.EventSentEvent();
+  eventSent.setInstanceid(instanceId);
+  eventSent.setName(name);
+  eventSent.setInput(getStringValue(encodedInput));
+
+  const event = new pb.HistoryEvent();
+  event.setEventid(eventId);
+  event.setTimestamp(ts);
+  event.setEventsent(eventSent);
+
+  return event;
+}
+
 export function newSuspendEvent(): pb.HistoryEvent {
   const ts = new Timestamp();
 
diff --git a/packages/durabletask-js/src/worker/orchestration-executor.ts b/packages/durabletask-js/src/worker/orchestration-executor.ts
index e081d32..0699e6d 100644
--- a/packages/durabletask-js/src/worker/orchestration-executor.ts
+++ b/packages/durabletask-js/src/worker/orchestration-executor.ts
@@ -13,6 +13,7 @@ import { Logger, ConsoleLogger } from "../types/logger.type";
 import { getName } from "../task";
 import * as WorkerLogs from "./logs";
 import { OrchestrationStateError } from "../task/exception/orchestration-state-error";
+import { NonDeterminismError } from "../task/exception/non-determinism-error";
 import { CompletableTask } from "../task/completable-task";
 import { RetryableTask } from "../task/retryable-task";
 import { RetryHandlerTask } from "../task/retry-handler-task";
@@ -162,6 +163,9 @@ export class OrchestrationExecutor {
         case pb.HistoryEvent.EventtypeCase.EVENTRAISED:
           await this.handleEventRaised(ctx, event);
           break;
+        case pb.HistoryEvent.EventtypeCase.EVENTSENT:
+          await this.handleEventSent(ctx, event);
+          break;
         case pb.HistoryEvent.EventtypeCase.EXECUTIONSUSPENDED:
           await this.handleExecutionSuspended(ctx, event);
           break;
@@ -455,6 +459,42 @@ export class OrchestrationExecutor {
     }
   }
 
+  private async handleEventSent(ctx: RuntimeOrchestrationContext, event: pb.HistoryEvent): Promise<void> {
+    // This history event confirms that a sendEvent action was successfully processed by the sidecar.
+    const eventId = event.getEventid();
+    const action = ctx._pendingActions[eventId];
+
+    const isSendEventAction = action?.hasSendevent();
+
+    if (!action) {
+      throw getNonDeterminismError(eventId, getName(ctx.sendEvent));
+    } else if (!isSendEventAction) {
+      const expectedMethodName = getName(ctx.sendEvent);
+      throw new NonDeterminismError(
+        `A previous execution called ${expectedMethodName} with ID=${eventId}, but the current execution is instead trying to call a different method as part of rebuilding its history.`,
+      );
+    }
+
+    const eventSent = event.getEventsent();
+    const expectedEventName = eventSent?.getName();
+    const sendEventAction = action.getSendevent()!;
+    const actualEventName = sendEventAction.getName();
+    if (expectedEventName !== actualEventName) {
+      throw getWrongActionNameError(eventId, getName(ctx.sendEvent), expectedEventName, actualEventName);
+    }
+
+    const expectedInstanceId = eventSent?.getInstanceid();
+    const actualInstanceId = sendEventAction.getInstance()?.getInstanceid();
+    if (expectedInstanceId !== actualInstanceId) {
+      throw new NonDeterminismError(
+        `Failed to restore orchestration state due to a history mismatch: A previous execution called ${getName(ctx.sendEvent)} with target instance '${expectedInstanceId}' and sequence number ${eventId}, but the current execution is instead trying to target instance '${actualInstanceId}' as part of rebuilding its history.`,
+      );
+    }
+
+    // Remove the action from the pending action list only after replay validation succeeds.
+    delete ctx._pendingActions[eventId];
+  }
+
   private async handleExecutionSuspended(ctx: RuntimeOrchestrationContext, _event: pb.HistoryEvent): Promise<void> {
     if (!this._isSuspended && !ctx._isReplaying) {
       WorkerLogs.orchestrationSuspended(this._logger, ctx._instanceId);
diff --git a/packages/durabletask-js/test/orchestration_executor.spec.ts b/packages/durabletask-js/test/orchestration_executor.spec.ts
index 599453f..a0b2edb 100644
--- a/packages/durabletask-js/test/orchestration_executor.spec.ts
+++ b/packages/durabletask-js/test/orchestration_executor.spec.ts
@@ -5,6 +5,7 @@ import { CompleteOrchestrationAction, OrchestratorAction } from "../src/proto/or
 import { OrchestrationContext } from "../src/task/context/orchestration-context";
 import {
   newEventRaisedEvent,
+  newEventSentEvent,
   newExecutionStartedEvent,
   newOrchestratorStartedEvent,
   newResumeEvent,
@@ -2119,6 +2120,176 @@ describe("Orchestration Executor", () => {
   });
 });
 
+describe("EventSent Handler", () => {
+  it("should remove sendEvent action from pendingActions on replay when EVENTSENT event is received", async () => {
+    // Orchestrator sends an event then calls an activity
+    const myActivity = () => "activity-result";
+    const orchestrator: TOrchestrator = async function* (ctx: OrchestrationContext): any {
+      ctx.sendEvent("target-instance", "my-event", { key: "value" });
+      const result = yield ctx.callActivity(myActivity);
+      return result;
+    };
+
+    const registry = new Registry();
+    const name = registry.addOrchestrator(orchestrator);
+    const activityName = registry.addActivity(myActivity);
+
+    // Simulate replay: oldEvents contain the execution start, EventSent confirmation,
+    // TaskScheduled confirmation, and task completion
+    const oldEvents = [
+      newOrchestratorStartedEvent(),
+      newExecutionStartedEvent(name, "test-instance"),
+      // EventSent confirms the sendEvent action (ID=1 since it's the first action)
+      newEventSentEvent(1, "target-instance", "my-event", JSON.stringify({ key: "value" })),
+      // TaskScheduled confirms the activity action (ID=2)
+      newTaskScheduledEvent(2, activityName),
+      newTaskCompletedEvent(2, JSON.stringify("activity-result")),
+    ];
+
+    const newEvents = [newOrchestratorStartedEvent()];
+
+    const executor = new OrchestrationExecutor(registry);
+    const result = await executor.execute("test-instance", oldEvents, newEvents);
+
+    // Only the complete action should remain - sendEvent should NOT be re-sent
+    expect(result.actions.length).toEqual(1);
+    const action = result.actions[0];
+    expect(action.hasCompleteorchestration()).toBe(true);
+    expect(action.getCompleteorchestration()?.getResult()?.getValue()).toEqual(
+      JSON.stringify("activity-result"),
+    );
+  });
+
+  it("should throw NonDeterminismError when EVENTSENT event name does not match sendEvent action", async () => {
+    const orchestrator: TOrchestrator = async function* (ctx: OrchestrationContext): any {
+      ctx.sendEvent("target-instance", "my-event", { key: "value" });
+      yield ctx.createTimer(1);
+    };
+
+    const registry = new Registry();
+    const name = registry.addOrchestrator(orchestrator);
+
+    const oldEvents = [
+      newOrchestratorStartedEvent(),
+      newExecutionStartedEvent(name, "test-instance"),
+      newEventSentEvent(1, "target-instance", "different-event", JSON.stringify({ key: "value" })),
+    ];
+
+    const executor = new OrchestrationExecutor(registry);
+    const result = await executor.execute("test-instance", oldEvents, [newOrchestratorStartedEvent()]);
+
+    const completeAction = result.actions.find((a) => a.hasCompleteorchestration());
+    expect(completeAction).toBeDefined();
+    expect(completeAction?.getCompleteorchestration()?.getOrchestrationstatus()).toEqual(
+      pb.OrchestrationStatus.ORCHESTRATION_STATUS_FAILED,
+    );
+    const failureDetails = completeAction?.getCompleteorchestration()?.getFailuredetails();
+    expect(failureDetails?.getErrortype()).toEqual("NonDeterminismError");
+    expect(failureDetails?.getErrormessage()).toContain("different-event");
+    expect(failureDetails?.getErrormessage()).toContain("my-event");
+  });
+
+  it("should throw NonDeterminismError when EVENTSENT target instance does not match sendEvent action", async () => {
+    const orchestrator: TOrchestrator = async function* (ctx: OrchestrationContext): any {
+      ctx.sendEvent("target-instance", "my-event", { key: "value" });
+      yield ctx.createTimer(1);
+    };
+
+    const registry = new Registry();
+    const name = registry.addOrchestrator(orchestrator);
+
+    const oldEvents = [
+      newOrchestratorStartedEvent(),
+      newExecutionStartedEvent(name, "test-instance"),
+      newEventSentEvent(1, "different-target", "my-event", JSON.stringify({ key: "value" })),
+    ];
+
+    const executor = new OrchestrationExecutor(registry);
+    const result = await executor.execute("test-instance", oldEvents, [newOrchestratorStartedEvent()]);
+
+    const completeAction = result.actions.find((a) => a.hasCompleteorchestration());
+    expect(completeAction).toBeDefined();
+    expect(completeAction?.getCompleteorchestration()?.getOrchestrationstatus()).toEqual(
+      pb.OrchestrationStatus.ORCHESTRATION_STATUS_FAILED,
+    );
+    const failureDetails = completeAction?.getCompleteorchestration()?.getFailuredetails();
+    expect(failureDetails?.getErrortype()).toEqual("NonDeterminismError");
+    expect(failureDetails?.getErrormessage()).toContain("different-target");
+    expect(failureDetails?.getErrormessage()).toContain("target-instance");
+  });
+
+  it("should throw NonDeterminismError when EVENTSENT event has no matching action", async () => {
+    // Orchestrator does NOT call sendEvent but gets an EVENTSENT history event
+    const myActivity = () => "result";
+    const orchestrator: TOrchestrator = async function* (ctx: OrchestrationContext): any {
+      const result = yield ctx.callActivity(myActivity);
+      return result;
+    };
+
+    const registry = new Registry();
+    const name = registry.addOrchestrator(orchestrator);
+    registry.addActivity(myActivity);
+
+    // oldEvents contain an EVENTSENT event with ID=99 that has no corresponding action
+    const oldEvents = [
+      newOrchestratorStartedEvent(),
+      newExecutionStartedEvent(name, "test-instance"),
+      newEventSentEvent(99, "target-instance", "phantom-event"),
+    ];
+
+    const newEvents = [newOrchestratorStartedEvent()];
+
+    const executor = new OrchestrationExecutor(registry);
+    const result = await executor.execute("test-instance", oldEvents, newEvents);
+
+    // Should fail with NonDeterminismError
+    const completeAction = result.actions.find((a) => a.hasCompleteorchestration());
+    expect(completeAction).toBeDefined();
+    expect(completeAction?.getCompleteorchestration()?.getOrchestrationstatus()).toEqual(
+      pb.OrchestrationStatus.ORCHESTRATION_STATUS_FAILED,
+    );
+    const failureDetails = completeAction?.getCompleteorchestration()?.getFailuredetails();
+    expect(failureDetails?.getErrortype()).toEqual("NonDeterminismError");
+    expect(failureDetails?.getErrormessage()).toMatch(/sendEvent.*ID=99/);
+  });
+
+  it("should throw when EVENTSENT event matches a non-sendEvent action type", async () => {
+    // Orchestrator calls an activity (creates ScheduleTask action with ID=1)
+    // but history says ID=1 is an EventSent event
+    const myActivity = () => "result";
+    const orchestrator: TOrchestrator = async function* (ctx: OrchestrationContext): any {
+      const result = yield ctx.callActivity(myActivity);
+      return result;
+    };
+
+    const registry = new Registry();
+    const name = registry.addOrchestrator(orchestrator);
+    registry.addActivity(myActivity);
+
+    // EVENTSENT event with ID=1 conflicts with ScheduleTask action at ID=1
+    const oldEvents = [
+      newOrchestratorStartedEvent(),
+      newExecutionStartedEvent(name, "test-instance"),
+      newEventSentEvent(1, "target-instance", "my-event"),
+    ];
+
+    const newEvents = [newOrchestratorStartedEvent()];
+
+    const executor = new OrchestrationExecutor(registry);
+    const result = await executor.execute("test-instance", oldEvents, newEvents);
+
+    // Should fail with NonDeterminismError (wrong action type)
+    const completeAction = result.actions.find((a) => a.hasCompleteorchestration());
+    expect(completeAction).toBeDefined();
+    expect(completeAction?.getCompleteorchestration()?.getOrchestrationstatus()).toEqual(
+      pb.OrchestrationStatus.ORCHESTRATION_STATUS_FAILED,
+    );
+    const failureDetails = completeAction?.getCompleteorchestration()?.getFailuredetails();
+    expect(failureDetails?.getErrortype()).toEqual("NonDeterminismError");
+    expect(failureDetails?.getErrormessage()).toMatch(/sendEvent/);
+  });
+});
+
 function getAndValidateSingleCompleteOrchestrationAction(
   result: OrchestrationExecutionResult,
 ): CompleteOrchestrationAction | undefined {