fix(googlechat): preserve replyToId across multi-payload sends for thread routing

Google Chat uses replyToId as persistent thread context (threadName),
similar to Slack (thread_ts) and Mattermost (rootId). The outbound
delivery core was consuming inherited replyToId after the first
successful send, orphaning subsequent payloads to the top level.

Add googlechat to the isThreadBasedChannel check so replyToId survives
across all payloads in a multi-payload response.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/infra/outbound/deliver.greptile-fixes.test.ts

@@ -272,6 +272,90 @@ describe("deliverOutboundPayloads Greptile fixes", () => {
     ]);
   });
 
+  it("preserves inherited replyToId across all googlechat sendPayload payloads (thread routing)", async () => {
+    const sendPayload = vi
+      .fn()
+      .mockResolvedValueOnce({ channel: "googlechat", messageId: "gc-1" })
+      .mockResolvedValueOnce({ channel: "googlechat", messageId: "gc-2" })
+      .mockResolvedValueOnce({ channel: "googlechat", messageId: "gc-3" });
+    const sendText = vi.fn();
+    const sendMedia = vi.fn();
+
+    setActivePluginRegistry(
+      createTestRegistry([
+        {
+          pluginId: "googlechat",
+          source: "test",
+          plugin: createOutboundTestPlugin({
+            id: "googlechat",
+            outbound: { deliveryMode: "direct", sendPayload, sendText, sendMedia },
+          }),
+        },
+      ]),
+    );
+
+    const results = await deliverOutboundPayloads({
+      cfg: {},
+      channel: "googlechat",
+      to: "spaces/AAAA",
+      payloads: [
+        { text: "first", channelData: { mode: "custom" } },
+        { text: "second", channelData: { mode: "custom" } },
+        { text: "third", channelData: { mode: "custom" } },
+      ],
+      replyToId: "spaces/AAAA/threads/BBBB",
+      skipQueue: true,
+    });
+
+    expect(sendPayload).toHaveBeenCalledTimes(3);
+    // All payloads must retain the thread identifier — consuming it after the
+    // first send would orphan subsequent payloads to the top level.
+    expect(sendPayload.mock.calls[0]?.[0]?.replyToId).toBe("spaces/AAAA/threads/BBBB");
+    expect(sendPayload.mock.calls[1]?.[0]?.replyToId).toBe("spaces/AAAA/threads/BBBB");
+    expect(sendPayload.mock.calls[2]?.[0]?.replyToId).toBe("spaces/AAAA/threads/BBBB");
+    expect(results).toEqual([
+      { channel: "googlechat", messageId: "gc-1" },
+      { channel: "googlechat", messageId: "gc-2" },
+      { channel: "googlechat", messageId: "gc-3" },
+    ]);
+  });
+
+  it("preserves inherited replyToId across googlechat text payloads (sendText path)", async () => {
+    const sendText = vi
+      .fn()
+      .mockResolvedValueOnce({ channel: "googlechat", messageId: "gc-t1", chatId: "spaces/X" })
+      .mockResolvedValueOnce({ channel: "googlechat", messageId: "gc-t2", chatId: "spaces/X" });
+    const sendMedia = vi.fn();
+
+    setActivePluginRegistry(
+      createTestRegistry([
+        {
+          pluginId: "googlechat",
+          source: "test",
+          plugin: createOutboundTestPlugin({
+            id: "googlechat",
+            outbound: { deliveryMode: "direct", sendText, sendMedia },
+          }),
+        },
+      ]),
+    );
+
+    const results = await deliverOutboundPayloads({
+      cfg: {},
+      channel: "googlechat",
+      to: "spaces/X",
+      payloads: [{ text: "chunk one" }, { text: "chunk two" }],
+      replyToId: "spaces/X/threads/T1",
+      skipQueue: true,
+    });
+
+    expect(sendText).toHaveBeenCalledTimes(2);
+    // Both text sends should receive replyToId for thread routing
+    expect(sendText.mock.calls[0]?.[0]?.replyToId).toBe("spaces/X/threads/T1");
+    expect(sendText.mock.calls[1]?.[0]?.replyToId).toBe("spaces/X/threads/T1");
+    expect(results).toHaveLength(2);
+  });
+
   it("retries replyToId on later non-signal media payloads after a best-effort failure", async () => {
     const sendText = vi.fn();
     const sendMedia = vi

src/infra/outbound/deliver.ts

@@ -738,10 +738,12 @@ async function deliverOutboundPayloadsCore(
     );
   }
   let replyConsumed = false;
-  // Slack and Mattermost use replyToId as persistent thread context (thread_ts
-  // and rootId respectively) that must survive across all payloads. Never
-  // consume inherited reply state for thread-based channels.
-  const isThreadBasedChannel = channel === "slack" || channel === "mattermost";
+  // Slack, Mattermost, and Google Chat use replyToId as persistent thread
+  // context (thread_ts, rootId, and threadName respectively) that must survive
+  // across all payloads. Never consume inherited reply state for thread-based
+  // channels.
+  const isThreadBasedChannel =
+    channel === "slack" || channel === "mattermost" || channel === "googlechat";
   const shouldConsumeReplyAfterSend = (replyTo: string | undefined) => {
     if (!replyTo) {
       return false;