fix(platform): fix SSE parser and prevent empty Discord messages

- Fix streamChat SSE parser: backend sends type=text_delta with delta
  field, not type=text with content field
- Collect full response before posting to Discord — empty async
  generators caused 'Cannot send empty message' spam that hit rate limits
- Show fallback message if CoPilot returns no text content

autogpt_platform/copilot-bot/src/bot.ts

@@ -206,9 +206,22 @@ async function handleCoPilotMessage(
       console.log(`[bot] Created session ${sessionId} for user ${userId.slice(-8)}`);
     }
 
-    // Stream CoPilot response — thread.post() accepts AsyncIterable<string>
+    // Stream CoPilot response — collect chunks, then post.
+    // We collect first because thread.post() with an empty stream
+    // causes Discord "Cannot send an empty message" errors.
     const stream = api.streamChat(userId, text, sessionId);
-    await thread.post(stream);
+    let response = "";
+    for await (const chunk of stream) {
+      response += chunk;
+    }
+
+    if (response.trim()) {
+      await thread.post(response);
+    } else {
+      await thread.post(
+        "I processed your message but didn't generate a response. Please try again."
+      );
+    }
   } catch (err: unknown) {
     const errMsg = err instanceof Error ? err.message : String(err);
     console.error(`[bot] CoPilot error for user ${userId.slice(-8)}:`, errMsg);

autogpt_platform/copilot-bot/src/platform-api.ts

@@ -193,15 +193,16 @@ export class PlatformAPI {
 
           try {
             const parsed = JSON.parse(data);
-            if (parsed.type === "text" && parsed.content) {
-              yield parsed.content;
-            } else if (typeof parsed === "string") {
-              yield parsed;
+            // Backend sends: text_delta (streaming chunks), text_start/text_end,
+            // start/finish (lifecycle), step_start/step_finish, error, etc.
+            if (parsed.type === "text_delta" && parsed.delta) {
+              yield parsed.delta;
+            } else if (parsed.type === "error" && parsed.content) {
+              yield `Error: ${parsed.content}`;
             }
+            // Ignore start/finish/step lifecycle events — they carry no text
           } catch {
-            if (data && data !== "[DONE]") {
-              yield data;
-            }
+            // Non-JSON data line — skip
           }
         }
       }