discord: support forum post creation via thread-create

Allow thread-create to create Discord forum posts by accepting initial content and appliedTagIds, and using POST /channels/{id}/threads.

src/agents/tools/discord-actions-messaging.ts

@@ -279,18 +279,31 @@ export async function handleDiscordMessagingAction(
       const channelId = resolveChannelId();
       const name = readStringParam(params, "name", { required: true });
       const messageId = readStringParam(params, "messageId");
+      // Optional initial content (required for forum posts).
+      const content = readStringParam(params, "content") ?? undefined;
+      // Optional applied tag ids (forum posts).
+      const appliedTagIds = Array.isArray(params.appliedTagIds)
+        ? params.appliedTagIds.filter((x) => typeof x === "string" && x.trim())
+        : undefined;
       const autoArchiveMinutesRaw = params.autoArchiveMinutes;
       const autoArchiveMinutes =
         typeof autoArchiveMinutesRaw === "number" && Number.isFinite(autoArchiveMinutesRaw)
           ? autoArchiveMinutesRaw
           : undefined;
+
       const thread = accountId
         ? await createThreadDiscord(
             channelId,
-            { name, messageId, autoArchiveMinutes },
+            { name, messageId, autoArchiveMinutes, content, appliedTagIds },
             { accountId },
           )
-        : await createThreadDiscord(channelId, { name, messageId, autoArchiveMinutes });
+        : await createThreadDiscord(channelId, {
+            name,
+            messageId,
+            autoArchiveMinutes,
+            content,
+            appliedTagIds,
+          });
       return jsonResult({ ok: true, thread });
     }
     case "threadList": {

src/channels/plugins/actions/discord/handle-action.ts

@@ -180,6 +180,10 @@ export async function handleDiscordMessageAction(
   if (action === "thread-create") {
     const name = readStringParam(params, "threadName", { required: true });
     const messageId = readStringParam(params, "messageId");
+    // Optional initial post content (required for forum post creation).
+    const content = readStringParam(params, "message");
+    // Optional forum tag ids.
+    const appliedTagIds = readStringArrayParam(params, "appliedTagIds");
     const autoArchiveMinutes = readNumberParam(params, "autoArchiveMin", {
       integer: true,
     });
@@ -190,6 +194,8 @@ export async function handleDiscordMessageAction(
         channelId: resolveChannelId(),
         name,
         messageId,
+        content,
+        appliedTagIds,
         autoArchiveMinutes,
       },
       cfg,

src/discord/send.messages.ts

@@ -94,10 +94,30 @@ export async function createThreadDiscord(
 ) {
   const rest = resolveDiscordRest(opts);
   const body: Record<string, unknown> = { name: payload.name };
+
   if (payload.autoArchiveMinutes) {
     body.auto_archive_duration = payload.autoArchiveMinutes;
   }
-  const route = Routes.threads(channelId, payload.messageId);
+
+  // Forum posts (channel type 15) require an initial message payload.
+  // If content is provided, create the thread with an initial post.
+  if (payload.content) {
+    body.message = { content: payload.content };
+    if (Array.isArray(payload.appliedTagIds) && payload.appliedTagIds.length) {
+      body.applied_tags = payload.appliedTagIds;
+    }
+    // NOTE: discord-api-types Routes doesn't currently expose a helper for
+    // POST /channels/{channel.id}/threads (it only exposes listing archived threads),
+    // so use the raw route string.
+    const route = `/channels/${channelId}/threads`;
+    return await rest.post(route, { body });
+  }
+
+  // Regular threads: create from an existing message when messageId is provided,
+  // otherwise create a standard thread in the channel.
+  const route = payload.messageId
+    ? Routes.threads(channelId, payload.messageId)
+    : `/channels/${channelId}/threads`;
   return await rest.post(route, { body });
 }
 

src/discord/send.types.ts

@@ -67,9 +67,16 @@ export type DiscordMessageEdit = {
 };
 
 export type DiscordThreadCreate = {
+  /** Optional message id to start a thread from (for classic threads). */
   messageId?: string;
+  /** Thread / forum post title. */
   name: string;
+  /** Auto-archive duration in minutes. */
   autoArchiveMinutes?: number;
+  /** Optional initial post content (required for forum post creation). */
+  content?: string;
+  /** Optional forum tag ids (applied tags). */
+  appliedTagIds?: string[];
 };
 
 export type DiscordThreadList = {