feat(agents): migrate subagents to event-driven scheduler (#17567)

packages/core/src/utils/toolCallContext.ts

@@ -0,0 +1,47 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { AsyncLocalStorage } from 'node:async_hooks';
+
+/**
+ * Contextual information for a tool call execution.
+ */
+export interface ToolCallContext {
+  /** The unique ID of the tool call. */
+  callId: string;
+  /** The ID of the scheduler managing the execution. */
+  schedulerId: string;
+  /** The ID of the parent tool call, if this is a nested execution (e.g., in a subagent). */
+  parentCallId?: string;
+}
+
+/**
+ * AsyncLocalStorage instance for tool call context.
+ */
+export const toolCallContext = new AsyncLocalStorage<ToolCallContext>();
+
+/**
+ * Runs a function within a tool call context.
+ *
+ * @param context The context to set.
+ * @param fn The function to run.
+ * @returns The result of the function.
+ */
+export function runWithToolCallContext<T>(
+  context: ToolCallContext,
+  fn: () => T,
+): T {
+  return toolCallContext.run(context, fn);
+}
+
+/**
+ * Retrieves the current tool call context.
+ *
+ * @returns The current ToolCallContext, or undefined if not in a context.
+ */
+export function getToolCallContext(): ToolCallContext | undefined {
+  return toolCallContext.getStore();
+}