fix(google): keep tool responses for gemini 3.1

Author: rahulmanuwas

.changeset/swift-pandas-juggle.md

@@ -0,0 +1,5 @@
+---
+'@livekit/agents-plugin-google': patch
+---
+
+fix Gemini 3.1 realtime tool-response handling during `updateChatCtx`

plugins/google/src/beta/realtime/realtime_api.test.ts

@@ -1,12 +1,15 @@
 // SPDX-FileCopyrightText: 2026 LiveKit, Inc.
 //
 // SPDX-License-Identifier: Apache-2.0
+import { llm } from '@livekit/agents';
 import { describe, expect, it } from 'vitest';
 import {
   buildGenerateReplyClientEvents,
   isRestrictedClientContentModel,
+  RealtimeModel,
   supportsServerSideChatContext,
 } from './realtime_api.js';
+import type * as api_proto from './api_proto.js';
 
 describe('Google realtime generateReply compatibility helpers', () => {
   it('detects restricted client-content models', () => {
@@ -135,4 +138,59 @@ describe('Google realtime generateReply compatibility helpers', () => {
     });
     expect(events[1]!.type).toBe('content');
   });
+
+  it('restricted models still send tool responses from updateChatCtx', async () => {
+    const session = new RealtimeModel({
+      apiKey: 'test',
+      model: 'gemini-3.1-flash-live-preview',
+    }).session() as unknown as {
+      activeSession?: unknown;
+      messageChannel: {
+        items: api_proto.ClientEvents[];
+        put(event: api_proto.ClientEvents): Promise<void>;
+      };
+      updateChatCtx(chatCtx: llm.ChatContext): Promise<void>;
+    };
+
+    const events: api_proto.ClientEvents[] = [];
+    Object.defineProperty(session, 'activeSession', {
+      configurable: true,
+      get: () => ({}),
+      set: () => undefined,
+    });
+    session.messageChannel.put = async (event) => {
+      events.push(event);
+    };
+
+    const chatCtx = llm.ChatContext.empty();
+    chatCtx.insert([
+      llm.ChatMessage.create({
+        role: 'assistant',
+        content: 'The tool finished successfully.',
+      }),
+      llm.FunctionCallOutput.create({
+        callId: 'call_123',
+        isError: false,
+        name: 'lookup_weather',
+        output: '{"temperature_c":21}',
+      }),
+    ]);
+
+    await session.updateChatCtx(chatCtx);
+
+    expect(events).toEqual([
+      {
+        type: 'tool_response',
+        value: {
+          functionResponses: [
+            {
+              id: 'call_123',
+              name: 'lookup_weather',
+              response: { output: '{"temperature_c":21}' },
+            },
+          ],
+        },
+      },
+    ]);
+  });
 });

plugins/google/src/beta/realtime/realtime_api.ts

@@ -77,7 +77,7 @@ function setsEqual<T>(a: Set<T>, b: Set<T>): boolean {
   return a.size === b.size && [...a].every((x) => b.has(x));
 }
 
-// Ref: python livekit-agents/livekit-plugins/livekit-plugins-google/livekit/plugins/google/realtime/api_proto.py
+// Restricted Gemini Live models reject mid-session sendClientContent.
 // Gemini 3.1+ rejects mid-session sendClientContent.
 // generateReply must use sendRealtimeInput, and the current JS SDK path cannot
 // keep chat context synchronized server-side for these models.
@@ -641,16 +641,6 @@ export class RealtimeSession extends llm.RealtimeSession {
     }
 
     if (appendCtx.items.length > 0) {
-      if (!supportsServerSideChatContext(this.options.model)) {
-        this.#logger.warn(
-          'updateChatCtx is not currently applied on restricted model ' +
-            this.options.model +
-            '. Storing chat context locally only until the JS SDK exposes a supported history path.',
-        );
-        this._chatCtx = chatCtx.copy();
-        return;
-      }
-
       const [turns] = await appendCtx
         .copy({
           excludeFunctionCall: true,
@@ -659,6 +649,24 @@ export class RealtimeSession extends llm.RealtimeSession {
 
       const toolResults = this.getToolResultsForRealtime(appendCtx, this.options.vertexai);
 
+      if (!supportsServerSideChatContext(this.options.model)) {
+        if (turns.length > 0) {
+          this.#logger.warn(
+            'updateChatCtx is not currently applied on restricted model ' +
+              this.options.model +
+              '. Storing chat context locally only until the JS SDK exposes a supported history path.',
+          );
+        }
+        if (toolResults) {
+          this.sendClientEvent({
+            type: 'tool_response',
+            value: toolResults,
+          });
+        }
+        this._chatCtx = chatCtx.copy();
+        return;
+      }
+
       if (turns.length > 0) {
         const shouldSendRealtimeText = this.pendingInterruptText;