Fix SSE parsing: read data: prefix + contentBlockDelta.delta.text

src/lambdas/agent-runner/handler.py

@@ -204,26 +204,38 @@ def handler(event, context):
 
     body = response.get('response')
     text_buffer = ''
+    leftover = ''
     if body is not None:
-        for chunk in body.iter_chunks():
-            if not chunk:
+        for raw_chunk in body.iter_chunks():
+            if not raw_chunk:
                 continue
-            try:
-                event = json.loads(chunk.decode('utf-8'))
-                # Strands streaming event: 'data' field contains text delta
-                delta = event.get('data', '') or event.get('text', '')
-                if delta:
-                    text_buffer += delta
-                    # Flush on paragraph or sentence break, or if buffer is large
-                    flush = (
-                        text_buffer.rstrip().endswith(('\n\n', '.\n', '!\n', '?\n'))
-                        or len(text_buffer) > 800
-                    )
-                    if flush and text_buffer.strip():
-                        send_telegram_direct(str(chat_id), bot_token, text_buffer.strip())
-                        text_buffer = ''
-            except (json.JSONDecodeError, UnicodeDecodeError):
-                pass
+            # AgentCore streams SSE format: "data: {...}\n\n"
+            text = leftover + raw_chunk.decode('utf-8', errors='replace')
+            parts = text.split('\n\n')
+            leftover = parts[-1]
+            for part in parts[:-1]:
+                for line in part.splitlines():
+                    if not line.startswith('data: '):
+                        continue
+                    data = line[6:].strip()
+                    if not data or data == '[DONE]':
+                        continue
+                    try:
+                        event = json.loads(data)
+                    except (json.JSONDecodeError, ValueError):
+                        continue
+                    # Extract text delta from contentBlockDelta
+                    delta = event.get('event', {}).get('contentBlockDelta', {}).get('delta', {})
+                    token = delta.get('text', '') or event.get('data', '')
+                    if token:
+                        text_buffer += token
+                        flush = (
+                            text_buffer.rstrip().endswith(('\n\n', '.\n', '!\n', '?\n'))
+                            or len(text_buffer) > 800
+                        )
+                        if flush and text_buffer.strip():
+                            send_telegram_direct(str(chat_id), bot_token, text_buffer.strip())
+                            text_buffer = ''
 
     # Flush any remaining text
     if text_buffer.strip() and bot_token: