Feat: Cleanup and Generalize determineAgentForResumption for LRO Session Resumption Routing

core/src/agents/functions.ts

@@ -8,7 +8,12 @@ import {Content, createUserContent, FunctionCall, Part} from '@google/genai';
 import {isEmpty} from 'lodash-es';
 
 import {InvocationContext} from '../agents/invocation_context.js';
-import {createEvent, Event, getFunctionCalls} from '../events/event.js';
+import {
+  createEvent,
+  Event,
+  getFunctionCalls,
+  getFunctionResponses,
+} from '../events/event.js';
 import {mergeEventActions} from '../events/event_actions.js';
 import {BaseTool} from '../tools/base_tool.js';
 import {ToolConfirmation} from '../tools/tool_confirmation.js';
@@ -564,3 +569,44 @@ export function mergeParallelFunctionResponseEvents(
 }
 
 // TODO - b/425992518: support function call in live connection.
+
+/**
+ * Finds the function call event that matches the function call ID.
+ * Mirrors Python ADK's `find_event_by_function_call_id`.
+ */
+export function findEventByFunctionCallId(
+  events: Event[],
+  functionCallId: string,
+  endIndex: number = events.length,
+): Event | undefined {
+  for (let i = endIndex - 1; i >= 0; i--) {
+    const event = events[i];
+    const functionCalls = getFunctionCalls(event);
+    for (const functionCall of functionCalls) {
+      if (functionCall.id === functionCallId) {
+        return event;
+      }
+    }
+  }
+  return undefined;
+}
+
+/**
+ * Finds the function call event that matches the function response ID of the last event.
+ * Mirrors Python ADK's `find_matching_function_call`.
+ */
+export function findMatchingFunctionCall(events: Event[]): Event | undefined {
+  if (!events.length) {
+    return undefined;
+  }
+  const lastEvent = events[events.length - 1];
+  const functionResponses = getFunctionResponses(lastEvent);
+  if (!functionResponses.length || !functionResponses[0].id) {
+    return undefined;
+  }
+  return findEventByFunctionCallId(
+    events,
+    functionResponses[0].id,
+    events.length - 1,
+  );
+}

core/src/apps/app.ts

@@ -6,6 +6,7 @@
 
 import {BaseAgent, isBaseAgent} from '../agents/base_agent.js';
 import {BasePlugin} from '../plugins/base_plugin.js';
+import {ResumabilityConfig} from './resumability_config.js';
 
 const VALID_APP_NAME_RE = /^[a-zA-Z][a-zA-Z0-9_-]*$/;
 
@@ -50,6 +51,7 @@ export interface AppOptions {
   name: string;
   rootAgent: BaseAgent;
   plugins?: BasePlugin[];
+  resumabilityConfig?: ResumabilityConfig;
 }
 
 /**
@@ -70,6 +72,7 @@ export class App {
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   readonly rootAgent: BaseAgent | any;
   readonly plugins: BasePlugin[];
+  readonly resumabilityConfig?: ResumabilityConfig;
 
   constructor(options: AppOptions) {
     validateAppName(options.name);
@@ -90,5 +93,6 @@ export class App {
     this.name = options.name;
     this.rootAgent = options.rootAgent;
     this.plugins = options.plugins ?? [];
+    this.resumabilityConfig = options.resumabilityConfig;
   }
 }

core/src/apps/resumability_config.ts

@@ -0,0 +1,36 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * The configuration of resumability for an application or runner.
+ *
+ * The "resumability" in ADK refers to the ability to:
+ * 1. pause an invocation upon a long-running function call.
+ * 2. resume an invocation from the last event, if it's paused or failed midway
+ * through.
+ */
+export interface ResumabilityConfig {
+  /**
+   * Whether the app/runner supports agent resumption.
+   * If enabled, resumption routing based on matching function responses will be active.
+   */
+  isResumable: boolean;
+}
+
+/**
+ * Creates a {@link ResumabilityConfig} with default values.
+ *
+ * @param params Optional partial {@link ResumabilityConfig} overriding defaults.
+ * @returns A merged {@link ResumabilityConfig} object.
+ */
+export function createResumabilityConfig(
+  params: Partial<ResumabilityConfig> = {},
+): ResumabilityConfig {
+  return {
+    isResumable: false,
+    ...params,
+  };
+}

core/src/common.ts

@@ -14,7 +14,11 @@ export type {
   SingleAgentCallback,
 } from './agents/base_agent.js';
 export {Context} from './agents/context.js';
-export {functionsExportedForTestingOnly} from './agents/functions.js';
+export {
+  findEventByFunctionCallId,
+  findMatchingFunctionCall,
+  functionsExportedForTestingOnly,
+} from './agents/functions.js';
 export {InvocationContext} from './agents/invocation_context.js';
 export type {InvocationContextParams} from './agents/invocation_context.js';
 export {LiveRequestQueue} from './agents/live_request_queue.js';
@@ -58,6 +62,8 @@ export {StreamingMode} from './agents/run_config.js';
 export type {RunConfig} from './agents/run_config.js';
 export {SequentialAgent, isSequentialAgent} from './agents/sequential_agent.js';
 export type {TranscriptionEntry} from './agents/transcription_entry.js';
+export {createResumabilityConfig} from './apps/resumability_config.js';
+export type {ResumabilityConfig} from './apps/resumability_config.js';
 export type {
   BaseArtifactService,
   DeleteArtifactRequest,
@@ -190,7 +196,13 @@ export type {
   ToolCallPolicyContext,
 } from './plugins/security_plugin.js';
 export {InMemoryRunner} from './runner/in_memory_runner.js';
-export {Runner, isRunner} from './runner/runner.js';
+export {
+  Runner,
+  determineAgentForResumption,
+  findEventByLastFunctionResponseId,
+  isRoutableLlmAgent,
+  isRunner,
+} from './runner/runner.js';
 export type {RunnerConfig} from './runner/runner.js';
 export {BaseSessionService} from './sessions/base_session_service.js';
 export type {

core/src/runner/in_memory_runner.ts

@@ -6,6 +6,7 @@
 
 import {BaseAgent} from '../agents/base_agent.js';
 import {App} from '../apps/app.js';
+import {ResumabilityConfig} from '../apps/resumability_config.js';
 import {InMemoryArtifactService} from '../artifacts/in_memory_artifact_service.js';
 import {InMemoryMemoryService} from '../memory/in_memory_memory_service.js';
 import {BasePlugin} from '../plugins/base_plugin.js';
@@ -37,18 +38,27 @@ export class InMemoryRunner extends Runner {
    * Creates a new InMemoryRunner instance.
    *
    * @param params The configuration for the runner.
+   * @param params.app An optional application instance to run.
    * @param params.agent The root agent to run.
    * @param params.appName The application name. Defaults to `'InMemoryRunner'`.
    * @param params.plugins An optional list of plugins.
-   * @param params.app An optional application instance to run.
+   * @param params.resumabilityConfig An optional resumability configuration.
    */
   constructor(params: {
     app?: App;
     agent?: BaseAgent;
     appName?: string;
     plugins?: BasePlugin[];
+    resumabilityConfig?: ResumabilityConfig;
   }) {
-    const {agent, appName = 'InMemoryRunner', plugins = [], app} = params;
+    const {
+      agent,
+      appName = 'InMemoryRunner',
+      plugins = [],
+      app,
+      resumabilityConfig,
+    } = params;
+
     super({
       app,
       appName,
@@ -57,6 +67,7 @@ export class InMemoryRunner extends Runner {
       artifactService: new InMemoryArtifactService(),
       sessionService: new InMemorySessionService(),
       memoryService: new InMemoryMemoryService(),
+      resumabilityConfig: app?.resumabilityConfig ?? resumabilityConfig,
     });
   }
 }