From 99cfa50451cc7bb8d4f03e06eb50b666d19e3830 Mon Sep 17 00:00:00 2001
From: Peter Steinberger <steipete@gmail.com>
Date: Fri, 24 Apr 2026 23:42:42 +0100
Subject: [PATCH] test(slack): cover first native stream thread target

---
 .../dispatch.preview-fallback.test.ts         | 43 ++++++++++++++++---
 .../dispatch.streaming.test.ts                | 11 +++++
 2 files changed, 49 insertions(+), 5 deletions(-)

diff --git a/extensions/slack/src/monitor/message-handler/dispatch.preview-fallback.test.ts b/extensions/slack/src/monitor/message-handler/dispatch.preview-fallback.test.ts
index 7f3f8342297..e75951452ed 100644
--- a/extensions/slack/src/monitor/message-handler/dispatch.preview-fallback.test.ts
+++ b/extensions/slack/src/monitor/message-handler/dispatch.preview-fallback.test.ts
@@ -30,6 +30,7 @@ class TestSlackStreamNotDeliveredError extends Error {
 let mockedNativeStreaming = false;
 let mockedBlockStreamingEnabled: boolean | undefined = false;
 let capturedReplyOptions: { disableBlockStreaming?: boolean } | undefined;
+let mockedReplyThreadTs: string | undefined = THREAD_TS;
 let mockedDispatchSequence: Array<{
   kind: "tool" | "block" | "final";
   payload: { text: string; isError?: boolean; mediaUrl?: string; mediaUrls?: string[] };
@@ -52,7 +53,15 @@ function createDraftStreamStub() {
   };
 }
 
-function createPreparedSlackMessage() {
+function createPreparedSlackMessage(params?: {
+  message?: Partial<{
+    channel: string;
+    ts: string;
+    thread_ts?: string;
+    user: string;
+  }>;
+  replyToMode?: "off" | "first" | "all" | "batched";
+}) {
   return {
     ctx: {
       cfg: {},
@@ -77,6 +86,7 @@ function createPreparedSlackMessage() {
       ts: "171234.111",
       thread_ts: THREAD_TS,
       user: "U123",
+      ...params?.message,
     },
     route: {
       agentId: "agent-1",
@@ -88,7 +98,7 @@ function createPreparedSlackMessage() {
     ctxPayload: {
       MessageThreadId: THREAD_TS,
     },
-    replyToMode: "all",
+    replyToMode: params?.replyToMode ?? "all",
     isDirectMessage: false,
     isRoomish: false,
     historyKey: "history-key",
@@ -248,13 +258,13 @@ vi.mock("../config.runtime.js", () => ({
 
 vi.mock("../replies.js", () => ({
   createSlackReplyDeliveryPlan: () => ({
-    peekThreadTs: () => THREAD_TS,
-    nextThreadTs: () => THREAD_TS,
+    peekThreadTs: () => mockedReplyThreadTs,
+    nextThreadTs: () => mockedReplyThreadTs,
     markSent: () => {},
   }),
   deliverReplies: deliverRepliesMock,
   readSlackReplyBlocks: () => undefined,
-  resolveSlackThreadTs: () => THREAD_TS,
+  resolveSlackThreadTs: () => mockedReplyThreadTs,
 }));
 
 vi.mock("../reply.runtime.js", () => ({
@@ -311,6 +321,7 @@ describe("dispatchPreparedSlackMessage preview fallback", () => {
     mockedNativeStreaming = false;
     mockedBlockStreamingEnabled = false;
     capturedReplyOptions = undefined;
+    mockedReplyThreadTs = THREAD_TS;
     mockedDispatchSequence = [{ kind: "final", payload: { text: FINAL_REPLY_TEXT } }];
 
     createSlackDraftStreamMock.mockReturnValue(createDraftStreamStub());
@@ -347,6 +358,28 @@ describe("dispatchPreparedSlackMessage preview fallback", () => {
     expect(capturedReplyOptions?.disableBlockStreaming).toBe(true);
   });
 
+  it("starts native streams in the first-reply thread for top-level channel messages", async () => {
+    mockedNativeStreaming = true;
+    mockedReplyThreadTs = "171234.111";
+    mockedDispatchSequence = [{ kind: "final", payload: { text: FINAL_REPLY_TEXT } }];
+
+    await dispatchPreparedSlackMessage(
+      createPreparedSlackMessage({
+        message: { thread_ts: undefined },
+        replyToMode: "all",
+      }),
+    );
+
+    expect(startSlackStreamMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        channel: "C123",
+        threadTs: "171234.111",
+        text: FINAL_REPLY_TEXT,
+      }),
+    );
+    expect(deliverRepliesMock).not.toHaveBeenCalled();
+  });
+
   it("keeps same-content tool and final payloads distinct after preview fallback", async () => {
     mockedDispatchSequence = [
       { kind: "tool", payload: { text: SAME_TEXT } },
diff --git a/extensions/slack/src/monitor/message-handler/dispatch.streaming.test.ts b/extensions/slack/src/monitor/message-handler/dispatch.streaming.test.ts
index c7d8ddfb078..8b66a680f27 100644
--- a/extensions/slack/src/monitor/message-handler/dispatch.streaming.test.ts
+++ b/extensions/slack/src/monitor/message-handler/dispatch.streaming.test.ts
@@ -156,6 +156,17 @@ describe("slack native streaming thread hint", () => {
     ).toBe("1000.2");
   });
 
+  it("uses the message timestamp for top-level channel replies when replyToMode=all", () => {
+    expect(
+      resolveSlackStreamingThreadHint({
+        replyToMode: "all",
+        incomingThreadTs: undefined,
+        messageTs: "1000.4",
+        isThreadReply: false,
+      }),
+    ).toBe("1000.4");
+  });
+
   it("uses the existing incoming thread regardless of replyToMode", () => {
     expect(
       resolveSlackStreamingThreadHint({