fix(discord): send initial message for non-forum thread creation

When creating a thread in a non-forum channel with the `content` parameter,
the content was silently ignored. This happened because only forum/media
channels support the `message` field in the thread creation request body.

This fix sends the initial message as a separate API call after the thread
is created, ensuring the content parameter works for all thread types.

Fixes the issue where `thread-create` with `message` parameter appeared
to succeed but the message never appeared in the thread.

src/discord/send.creates-thread.test.ts

@@ -107,6 +107,61 @@ describe("sendMessageDiscord", () => {
     );
   });
 
+  it("sends initial message for non-forum threads with content", async () => {
+    const { rest, getMock, postMock } = makeDiscordRest();
+    getMock.mockResolvedValue({ type: ChannelType.GuildText });
+    postMock.mockResolvedValue({ id: "t1" });
+    await createThreadDiscord(
+      "chan1",
+      { name: "thread", content: "Hello thread!" },
+      { rest, token: "t" },
+    );
+    expect(postMock).toHaveBeenCalledTimes(2);
+    // First call: create thread
+    expect(postMock).toHaveBeenNthCalledWith(
+      1,
+      Routes.threads("chan1"),
+      expect.objectContaining({
+        body: expect.objectContaining({ name: "thread", type: ChannelType.PublicThread }),
+      }),
+    );
+    // Second call: send message to thread
+    expect(postMock).toHaveBeenNthCalledWith(
+      2,
+      Routes.channelMessages("t1"),
+      expect.objectContaining({
+        body: { content: "Hello thread!" },
+      }),
+    );
+  });
+
+  it("sends initial message for message-attached threads with content", async () => {
+    const { rest, getMock, postMock } = makeDiscordRest();
+    postMock.mockResolvedValue({ id: "t1" });
+    await createThreadDiscord(
+      "chan1",
+      { name: "thread", messageId: "m1", content: "Discussion here" },
+      { rest, token: "t" },
+    );
+    // Should not detect channel type for message-attached threads
+    expect(getMock).not.toHaveBeenCalled();
+    expect(postMock).toHaveBeenCalledTimes(2);
+    // First call: create thread from message
+    expect(postMock).toHaveBeenNthCalledWith(
+      1,
+      Routes.threads("chan1", "m1"),
+      expect.objectContaining({ body: { name: "thread" } }),
+    );
+    // Second call: send message to thread
+    expect(postMock).toHaveBeenNthCalledWith(
+      2,
+      Routes.channelMessages("t1"),
+      expect.objectContaining({
+        body: { content: "Discussion here" },
+      }),
+    );
+  });
+
   it("lists active threads by guild", async () => {
     const { rest, getMock } = makeDiscordRest();
     getMock.mockResolvedValue({ threads: [] });

src/discord/send.messages.ts

@@ -134,7 +134,17 @@ export async function createThreadDiscord(
   const route = payload.messageId
     ? Routes.threads(channelId, payload.messageId)
     : Routes.threads(channelId);
-  return await rest.post(route, { body });
+  const thread = (await rest.post(route, { body })) as { id: string };
+
+  // For non-forum channels, send the initial message separately after thread creation.
+  // Forum channels handle this via the `message` field in the request body.
+  if (!isForumLike && payload.content?.trim()) {
+    await rest.post(Routes.channelMessages(thread.id), {
+      body: { content: payload.content },
+    });
+  }
+
+  return thread;
 }
 
 export async function listThreadsDiscord(payload: DiscordThreadList, opts: DiscordReactOpts = {}) {