fix(googlechat): space events response and thread context

Two fixes for Google Chat reliability:

1. Space Events Response (Fixes 'Can't handle app response' error):
   - Return proper JSON response for non-MESSAGE events in groups
   - Handles ADDED_TO_SPACE, REMOVED_FROM_SPACE, etc.
   - Previously returned empty '{}' which caused errors

2. Thread Reply Context (Adds missing context):
   - Add threadReply field to GoogleChatMessage type
   - Add quotedMessageMetadata field for quoted messages
   - Pass IsThreadReply and QuotedMessageId to agent context
   - Agent now knows when a message is a reply vs root message

Both fixes improve Google Chat reliability and agent context awareness.

extensions/googlechat/src/monitor.ts

@@ -264,6 +264,19 @@ export async function handleGoogleChatWebhookRequest(
   }
 
   selected.statusSink?.({ lastInboundAt: Date.now() });
+
+  // For synchronous responses in spaces, handle non-MESSAGE events immediately
+  const evtType = (event.type ?? (event as { eventType?: string }).eventType)?.toUpperCase();
+  const isGroup = event.space?.type?.toUpperCase() !== "DM";
+
+  // For non-MESSAGE events in groups (like ADDED_TO_SPACE), return an acknowledgment
+  if (isGroup && evtType !== "MESSAGE") {
+    res.statusCode = 200;
+    res.setHeader("Content-Type", "application/json");
+    res.end(JSON.stringify({ text: "Hello! I'm ready to help. 🦞" }));
+    return true;
+  }
+
   processGoogleChatEvent(event, selected).catch((err) => {
     selected?.runtime.error?.(
       `[${selected.account.accountId}] Google Chat webhook failed: ${String(err)}`,
@@ -642,6 +655,9 @@ async function processMessageWithPipeline(params: {
     GroupSystemPrompt: isGroup ? groupSystemPrompt : undefined,
     OriginatingChannel: "googlechat",
     OriginatingTo: `googlechat:${spaceId}`,
+    // Thread reply context
+    IsThreadReply: message.threadReply,
+    QuotedMessageId: message.quotedMessageMetadata?.name,
   });
 
   void core.channel.session

extensions/googlechat/src/types.ts

@@ -47,6 +47,11 @@ export type GoogleChatAnnotation = {
   customEmojiMetadata?: Record<string, unknown>;
 };
 
+export type GoogleChatQuotedMessageMetadata = {
+  name?: string;
+  lastUpdateTime?: string;
+};
+
 export type GoogleChatMessage = {
   name?: string;
   text?: string;
@@ -55,6 +60,10 @@ export type GoogleChatMessage = {
   thread?: GoogleChatThread;
   attachment?: GoogleChatAttachment[];
   annotations?: GoogleChatAnnotation[];
+  /** True if this message is a reply in a thread */
+  threadReply?: boolean;
+  /** Metadata about the quoted/original message being replied to */
+  quotedMessageMetadata?: GoogleChatQuotedMessageMetadata;
 };
 
 export type GoogleChatEvent = {