fix(slack extension): preserve thread IDs for read + outbound delivery (#23836)

* Slack Extension: preserve thread IDs in reads and outbound sends

* Slack extension: fix threadTs typing and action test context

* Update CHANGELOG.md

extensions/slack/src/channel.test.ts

@@ -0,0 +1,106 @@
+import { describe, expect, it, vi } from "vitest";
+
+const handleSlackActionMock = vi.fn();
+
+vi.mock("./runtime.js", () => ({
+  getSlackRuntime: () => ({
+    channel: {
+      slack: {
+        handleSlackAction: handleSlackActionMock,
+      },
+    },
+  }),
+}));
+
+import { slackPlugin } from "./channel.js";
+
+describe("slackPlugin actions", () => {
+  it("forwards read threadId to Slack action handler", async () => {
+    handleSlackActionMock.mockResolvedValueOnce({ messages: [], hasMore: false });
+    const handleAction = slackPlugin.actions?.handleAction;
+    expect(handleAction).toBeDefined();
+
+    await handleAction!({
+      action: "read",
+      channel: "slack",
+      accountId: "default",
+      cfg: {},
+      params: {
+        channelId: "C123",
+        threadId: "1712345678.123456",
+      },
+    });
+
+    expect(handleSlackActionMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        action: "readMessages",
+        channelId: "C123",
+        threadId: "1712345678.123456",
+      }),
+      {},
+      undefined,
+    );
+  });
+});
+
+describe("slackPlugin outbound", () => {
+  const cfg = {
+    channels: {
+      slack: {
+        botToken: "xoxb-test",
+        appToken: "xapp-test",
+      },
+    },
+  };
+
+  it("uses threadId as threadTs fallback for sendText", async () => {
+    const sendSlack = vi.fn().mockResolvedValue({ messageId: "m-text" });
+    const sendText = slackPlugin.outbound?.sendText;
+    expect(sendText).toBeDefined();
+
+    const result = await sendText!({
+      cfg,
+      to: "C123",
+      text: "hello",
+      accountId: "default",
+      threadId: "1712345678.123456",
+      deps: { sendSlack },
+    });
+
+    expect(sendSlack).toHaveBeenCalledWith(
+      "C123",
+      "hello",
+      expect.objectContaining({
+        threadTs: "1712345678.123456",
+      }),
+    );
+    expect(result).toEqual({ channel: "slack", messageId: "m-text" });
+  });
+
+  it("prefers replyToId over threadId for sendMedia", async () => {
+    const sendSlack = vi.fn().mockResolvedValue({ messageId: "m-media" });
+    const sendMedia = slackPlugin.outbound?.sendMedia;
+    expect(sendMedia).toBeDefined();
+
+    const result = await sendMedia!({
+      cfg,
+      to: "C999",
+      text: "caption",
+      mediaUrl: "https://example.com/image.png",
+      accountId: "default",
+      replyToId: "1712000000.000001",
+      threadId: "1712345678.123456",
+      deps: { sendSlack },
+    });
+
+    expect(sendSlack).toHaveBeenCalledWith(
+      "C999",
+      "caption",
+      expect.objectContaining({
+        mediaUrl: "https://example.com/image.png",
+        threadTs: "1712000000.000001",
+      }),
+    );
+    expect(result).toEqual({ channel: "slack", messageId: "m-media" });
+  });
+});

extensions/slack/src/channel.ts

@@ -245,6 +245,7 @@ export const slackPlugin: ChannelPlugin<ResolvedSlackAccount> = {
       await handleSlackMessageAction({
         providerId: meta.id,
         ctx,
+        includeReadThreadId: true,
         invoke: async (action, cfg, toolContext) =>
           await getSlackRuntime().channel.slack.handleSlackAction(action, cfg, toolContext),
       }),
@@ -324,28 +325,30 @@ export const slackPlugin: ChannelPlugin<ResolvedSlackAccount> = {
     deliveryMode: "direct",
     chunker: null,
     textChunkLimit: 4000,
-    sendText: async ({ to, text, accountId, deps, replyToId, cfg }) => {
+    sendText: async ({ to, text, accountId, deps, replyToId, threadId, cfg }) => {
       const send = deps?.sendSlack ?? getSlackRuntime().channel.slack.sendMessageSlack;
       const account = resolveSlackAccount({ cfg, accountId });
       const token = getTokenForOperation(account, "write");
       const botToken = account.botToken?.trim();
       const tokenOverride = token && token !== botToken ? token : undefined;
+      const threadTsValue = replyToId ?? threadId;
       const result = await send(to, text, {
-        threadTs: replyToId ?? undefined,
+        threadTs: threadTsValue != null ? String(threadTsValue) : undefined,
         accountId: accountId ?? undefined,
         ...(tokenOverride ? { token: tokenOverride } : {}),
       });
       return { channel: "slack", ...result };
     },
-    sendMedia: async ({ to, text, mediaUrl, accountId, deps, replyToId, cfg }) => {
+    sendMedia: async ({ to, text, mediaUrl, accountId, deps, replyToId, threadId, cfg }) => {
       const send = deps?.sendSlack ?? getSlackRuntime().channel.slack.sendMessageSlack;
       const account = resolveSlackAccount({ cfg, accountId });
       const token = getTokenForOperation(account, "write");
       const botToken = account.botToken?.trim();
       const tokenOverride = token && token !== botToken ? token : undefined;
+      const threadTsValue = replyToId ?? threadId;
       const result = await send(to, text, {
         mediaUrl,
-        threadTs: replyToId ?? undefined,
+        threadTs: threadTsValue != null ? String(threadTsValue) : undefined,
         accountId: accountId ?? undefined,
         ...(tokenOverride ? { token: tokenOverride } : {}),
       });