Discord: preserve media caption whitespace

src/discord/send.sends-basic-channel-messages.test.ts

@@ -246,6 +246,32 @@ describe("sendMessageDiscord", () => {
     );
   });
 
+  it("sends media with empty text without content field", async () => {
+    const { rest, postMock } = makeRest();
+    postMock.mockResolvedValue({ id: "msg", channel_id: "789" });
+    const res = await sendMessageDiscord("channel:789", "", {
+      rest,
+      token: "t",
+      mediaUrl: "file:///tmp/photo.jpg",
+    });
+    expect(res.messageId).toBe("msg");
+    const body = postMock.mock.calls[0]?.[1]?.body;
+    expect(body).not.toHaveProperty("content");
+    expect(body).toHaveProperty("files");
+  });
+
+  it("preserves whitespace in media captions", async () => {
+    const { rest, postMock } = makeRest();
+    postMock.mockResolvedValue({ id: "msg", channel_id: "789" });
+    await sendMessageDiscord("channel:789", "  spaced  ", {
+      rest,
+      token: "t",
+      mediaUrl: "file:///tmp/photo.jpg",
+    });
+    const body = postMock.mock.calls[0]?.[1]?.body;
+    expect(body).toHaveProperty("content", "  spaced  ");
+  });
+
   it("includes message_reference when replying", async () => {
     const { rest, postMock } = makeRest();
     postMock.mockResolvedValue({ id: "msg1", channel_id: "789" });

src/discord/send.shared.ts

@@ -361,13 +361,17 @@ async function sendDiscordMedia(
   const media = await loadWebMedia(mediaUrl);
   const chunks = text ? buildDiscordTextChunks(text, { maxLinesPerMessage, chunkMode }) : [];
   const caption = chunks[0] ?? "";
+  const hasCaption = caption.trim().length > 0;
   const messageReference = replyTo ? { message_id: replyTo, fail_if_not_exists: false } : undefined;
   const res = (await request(
     () =>
       rest.post(Routes.channelMessages(channelId), {
         body: {
-          content: caption || undefined,
-          message_reference: messageReference,
+          // Only include content when there is actual text; Discord rejects
+          // media-only messages that carry an empty or undefined content field
+          // when sent as multipart/form-data. Preserve whitespace in captions.
+          ...(hasCaption ? { content: caption } : {}),
+          ...(messageReference ? { message_reference: messageReference } : {}),
           ...(embeds?.length ? { embeds } : {}),
           files: [
             {