diff --git a/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.test.ts b/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.test.ts
index d66084329dc..4c221b55189 100644
--- a/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.test.ts
+++ b/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.test.ts
@@ -70,12 +70,20 @@ describe("Codex ACPX runtime adapter", () => {
     const admittedFirst = port.startTurn({ text: "First", requestId: "turn-1", onExtensionRequest: request, onExtensionNotification: notification });
     const signal = new AbortController().signal;
     await expect(created.onExtensionRequest!("cursor/ask_question", { sessionId: "backend-1" }, { requestId: 0, signal })).resolves.toEqual({ requestId: 0 });
+    const sessionless = { toolCallId: "native-cursor-plan", plan: "Review the complete plan" };
+    await expect(created.onExtensionRequest!("cursor/create_plan", sessionless, { requestId: "plan", signal })).resolves.toEqual({ requestId: "plan" });
+    expect(request).toHaveBeenLastCalledWith("cursor/create_plan", { ...sessionless, sessionId: "backend-1" }, expect.objectContaining({ requestId: "plan" }));
+    expect(sessionless).not.toHaveProperty("sessionId");
     await expect(created.onExtensionRequest!("pi/steer", {}, { requestId: 1, signal })).rejects.toThrow("admitted active turn");
     await expect(created.onExtensionRequest!("cursor/ask_question", { sessionId: "other" }, { requestId: 1, signal })).rejects.toThrow("admitted active turn");
     created.onExtensionNotification!("cursor/task", { sessionId: "backend-1", taskId: "t" });
     created.onExtensionNotification!("cursor/task", { sessionId: "other" });
     created.onExtensionNotification!("cursor/ask_question", { sessionId: "backend-1" });
     expect(notification).toHaveBeenCalledExactlyOnceWith("cursor/task", { sessionId: "backend-1", taskId: "t" });
+    created.onExtensionNotification!("cursor/task", { toolCallId: "native-child" });
+    expect(notification).toHaveBeenLastCalledWith("cursor/task", { sessionId: "backend-1", toolCallId: "native-child" });
+    created.onExtensionNotification!("cursor/task", { sessionId: "agent-1" });
+    expect(notification).toHaveBeenCalledTimes(2);
     request.mockImplementationOnce(() => new Promise(() => undefined));
     const pending = created.onExtensionRequest!("cursor/ask_question", {}, { requestId: 2, signal });
     const rejected = expect(pending).rejects.toThrow("expired");
diff --git a/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.ts b/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.ts
index 77d540520e0..73d0bbfbf07 100644
--- a/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.ts
+++ b/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.ts
@@ -84,6 +84,7 @@ interface AcpxRuntimeGoalState {
 
 interface AcpxRuntimeExtensionTurn {
   requestId: string;
+  sessionId: string;
   controller: AbortController;
   signal: AbortSignal;
   promptStarted: Promise<void>;
@@ -320,7 +321,10 @@ export async function openQualifiedAcpxRuntime(
         throw new Error("ACPX extension request does not own an admitted active turn");
       }
       const signal = AbortSignal.any([active.signal, context.signal]);
-      const response = await abortableExtensionResult(active.onRequest(method, params, { requestId: context.requestId, signal }), signal);
+      // Cursor's native extensions omit sessionId. Only after admission may
+      // that omission inherit this exact prompt's ACP wire session identity.
+      const boundParams = params.sessionId === undefined ? { ...params, sessionId: active.sessionId } : params;
+      const response = await abortableExtensionResult(active.onRequest(method, boundParams, { requestId: context.requestId, signal }), signal);
       signal.throwIfAborted();
       if (!ownsExtensionTurn(active, params)) throw new Error("ACPX extension request turn expired");
       return response;
@@ -328,7 +332,7 @@ export async function openQualifiedAcpxRuntime(
     onExtensionNotification: (method, params) => {
       const active = extensionBoundary.active;
       if (!extensionNotifications.has(method) || !active?.onNotification || !ownsExtensionTurn(active, params)) return;
-      active.onNotification(method, params);
+      active.onNotification(method, params.sessionId === undefined ? { ...params, sessionId: active.sessionId } : params);
     },
     nonInteractivePermissions: "fail",
     permissionPolicy: {
@@ -1316,7 +1320,7 @@ function runtimePort(
       const approval = new AbortController();
       const controller = new AbortController();
       const extensionTurn: AcpxRuntimeExtensionTurn = {
-        requestId: input.requestId, controller,
+        requestId: input.requestId, sessionId: identity.backendSessionId, controller,
         signal: input.signal ? AbortSignal.any([controller.signal, input.signal, approval.signal]) : AbortSignal.any([controller.signal, approval.signal]),
         promptStarted: Promise.resolve(),
         onRequest: input.onExtensionRequest, onNotification: input.onExtensionNotification,