feat(core): introduce remote agent infrastructure and rename local executor (#15110)

packages/core/src/agents/remote-invocation.ts

@@ -0,0 +1,48 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {
+  BaseToolInvocation,
+  type ToolResult,
+  type ToolCallConfirmationDetails,
+} from '../tools/tools.js';
+import type { AgentInputs, RemoteAgentDefinition } from './types.js';
+import type { MessageBus } from '../confirmation-bus/message-bus.js';
+
+/**
+ * A tool invocation that proxies to a remote A2A agent.
+ *
+ * This implementation bypasses the local `LocalAgentExecutor` loop and directly
+ * invokes the configured A2A tool.
+ */
+export class RemoteAgentInvocation extends BaseToolInvocation<
+  AgentInputs,
+  ToolResult
+> {
+  constructor(
+    private readonly definition: RemoteAgentDefinition,
+    params: AgentInputs,
+    messageBus?: MessageBus,
+  ) {
+    super(params, messageBus, definition.name, definition.displayName);
+  }
+
+  getDescription(): string {
+    return `Calling remote agent ${this.definition.displayName ?? this.definition.name}`;
+  }
+
+  protected override async getConfirmationDetails(
+    _abortSignal: AbortSignal,
+  ): Promise<ToolCallConfirmationDetails | false> {
+    // TODO: Implement confirmation logic for remote agents.
+    return false;
+  }
+
+  async execute(_signal: AbortSignal): Promise<ToolResult> {
+    // TODO: Implement remote agent invocation logic.
+    throw new Error(`Remote agent invocation not implemented.`);
+  }
+}