fix(streaming): ensure process_stream returns non-empty message content

Author: Ratish1

src/strands/event_loop/streaming.py

@@ -413,6 +413,9 @@ async def process_stream(
         elif "redactContent" in chunk:
             handle_redact_content(chunk["redactContent"], state)
 
+    if not state["message"]["content"]:
+        state["message"]["content"].append({"text": ""})
+
     yield ModelStopReason(stop_reason=stop_reason, message=state["message"], usage=usage, metrics=metrics)
 
 

tests/strands/event_loop/test_streaming.py

@@ -578,7 +578,7 @@ def test_extract_usage_metrics_empty_metadata():
                         "end_turn",
                         {
                             "role": "assistant",
-                            "content": [],
+                            "content": [{"text": ""}],
                         },
                         {"inputTokens": 0, "outputTokens": 0, "totalTokens": 0},
                         {"latencyMs": 0, "timeToFirstByteMs": 0},