diff --git a/packages/durabletask-js/src/testing/in-memory-backend.ts b/packages/durabletask-js/src/testing/in-memory-backend.ts
index 66cb406..a0ca836 100644
--- a/packages/durabletask-js/src/testing/in-memory-backend.ts
+++ b/packages/durabletask-js/src/testing/in-memory-backend.ts
@@ -4,6 +4,7 @@
 import * as pb from "../proto/orchestrator_service_pb";
 import * as pbh from "../utils/pb-helper.util";
 import { OrchestrationStatus as ClientOrchestrationStatus } from "../orchestration/enum/orchestration-status.enum";
+import { ParentOrchestrationInstance } from "../types/parent-orchestration-instance.type";
 
 /**
  * Internal orchestration instance state stored by the in-memory backend.
@@ -82,6 +83,7 @@ export class InMemoryOrchestrationBackend {
     name: string,
     input?: string,
     scheduledStartTime?: Date,
+    parentInstance?: ParentOrchestrationInstance,
   ): string {
     if (this.instances.has(instanceId)) {
       throw new Error(`Orchestration instance '${instanceId}' already exists`);
@@ -104,7 +106,7 @@ export class InMemoryOrchestrationBackend {
 
     // Add initial events to start the orchestration
     const orchestratorStarted = pbh.newOrchestratorStartedEvent(startTime);
-    const executionStarted = pbh.newExecutionStartedEvent(name, instanceId, input);
+    const executionStarted = pbh.newExecutionStartedEvent(name, instanceId, input, parentInstance);
 
     instance.pendingEvents.push(orchestratorStarted);
     instance.pendingEvents.push(executionStarted);
@@ -580,9 +582,13 @@ export class InMemoryOrchestrationBackend {
       instance.status = pb.OrchestrationStatus.ORCHESTRATION_STATUS_RUNNING;
     }
 
-    // Create the sub-orchestration
+    // Create the sub-orchestration with parent instance info
     try {
-      this.createInstance(subInstanceId, name, input);
+      this.createInstance(subInstanceId, name, input, undefined, {
+        name: instance.name,
+        instanceId: instance.instanceId,
+        taskScheduledId: taskId,
+      });
 
       // Watch for sub-orchestration completion
       this.watchSubOrchestration(instance.instanceId, subInstanceId, taskId);
diff --git a/packages/durabletask-js/test/in-memory-backend.spec.ts b/packages/durabletask-js/test/in-memory-backend.spec.ts
index 81a82a8..0374170 100644
--- a/packages/durabletask-js/test/in-memory-backend.spec.ts
+++ b/packages/durabletask-js/test/in-memory-backend.spec.ts
@@ -196,6 +196,57 @@ describe("In-Memory Backend", () => {
     expect(state?.serializedOutput).toContain("caught:");
   });
 
+  it("should set parent instance info on sub-orchestrations", async () => {
+    let capturedParent: import("../src").ParentOrchestrationInstance | undefined;
+
+    const childOrchestrator: TOrchestrator = async (ctx: OrchestrationContext) => {
+      capturedParent = ctx.parent;
+      return "child-done";
+    };
+
+    const parentOrchestrator: TOrchestrator = async function* (ctx: OrchestrationContext): any {
+      const result = yield ctx.callSubOrchestrator(childOrchestrator);
+      return result;
+    };
+
+    worker.addOrchestrator(childOrchestrator);
+    worker.addOrchestrator(parentOrchestrator);
+    await worker.start();
+
+    const id = await client.scheduleNewOrchestration(parentOrchestrator);
+    const state = await client.waitForOrchestrationCompletion(id, true, 10);
+
+    expect(state).toBeDefined();
+    expect(state?.runtimeStatus).toEqual(OrchestrationStatus.COMPLETED);
+
+    // Verify parent instance info was populated on the sub-orchestration context
+    expect(capturedParent).toBeDefined();
+    expect(capturedParent?.name).toEqual(getName(parentOrchestrator));
+    expect(capturedParent?.instanceId).toEqual(id);
+    expect(typeof capturedParent?.taskScheduledId).toEqual("number");
+  });
+
+  it("should not set parent instance info on top-level orchestrations", async () => {
+    let capturedParent: import("../src").ParentOrchestrationInstance | undefined;
+
+    const topLevelOrchestrator: TOrchestrator = async (ctx: OrchestrationContext) => {
+      capturedParent = ctx.parent;
+      return "done";
+    };
+
+    worker.addOrchestrator(topLevelOrchestrator);
+    await worker.start();
+
+    const id = await client.scheduleNewOrchestration(topLevelOrchestrator);
+    const state = await client.waitForOrchestrationCompletion(id, true, 10);
+
+    expect(state).toBeDefined();
+    expect(state?.runtimeStatus).toEqual(OrchestrationStatus.COMPLETED);
+
+    // Top-level orchestrations should have no parent
+    expect(capturedParent).toBeUndefined();
+  });
+
   it("should handle external events", async () => {
     const orchestrator: TOrchestrator = async function* (ctx: OrchestrationContext): any {
       const value = yield ctx.waitForExternalEvent("my_event");