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fix: append blank text content if assistant content is empty #677

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Merged
merged 1 commit into from
Aug 18, 2025
Merged

fix: append blank text content if assistant content is empty #677

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6 changes: 3 additions & 3 deletions src/strands/event_loop/streaming.py
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Original file line number Diff line number Diff line change
Expand Up @@ -40,10 +40,12 @@ def remove_blank_messages_content_text(messages: Messages) -> Messages:
# only modify assistant messages
if "role" in message and message["role"] != "assistant":
continue

if "content" in message:
content = message["content"]
has_tool_use = any("toolUse" in item for item in content)
if len(content) == 0:
content.append({"text": "[blank text]"})
continue

if has_tool_use:
# Remove blank 'text' items for assistant messages
Expand Down Expand Up @@ -272,7 +274,6 @@ async def process_stream(chunks: AsyncIterable[StreamEvent]) -> AsyncGenerator[d

async for chunk in chunks:
yield {"callback": {"event": chunk}}

if "messageStart" in chunk:
state["message"] = handle_message_start(chunk["messageStart"], state["message"])
elif "contentBlockStart" in chunk:
Expand Down Expand Up @@ -312,7 +313,6 @@ async def stream_messages(
logger.debug("model=<%s> | streaming messages", model)

messages = remove_blank_messages_content_text(messages)

chunks = model.stream(messages, tool_specs if tool_specs else None, system_prompt)

async for event in process_stream(chunks):
Expand Down
2 changes: 2 additions & 0 deletions tests/strands/event_loop/test_streaming.py
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Expand Up @@ -26,13 +26,15 @@ def moto_autouse(moto_env, moto_mock_aws):
{"role": "assistant", "content": [{"text": "a"}, {"text": " \n"}, {"toolUse": {}}]},
{"role": "assistant", "content": [{"text": ""}, {"toolUse": {}}]},
{"role": "assistant", "content": [{"text": "a"}, {"text": " \n"}]},
{"role": "assistant", "content": []},
{"role": "assistant"},
{"role": "user", "content": [{"text": " \n"}]},
],
[
{"role": "assistant", "content": [{"text": "a"}, {"toolUse": {}}]},
{"role": "assistant", "content": [{"toolUse": {}}]},
{"role": "assistant", "content": [{"text": "a"}, {"text": "[blank text]"}]},
{"role": "assistant", "content": [{"text": "[blank text]"}]},
{"role": "assistant"},
{"role": "user", "content": [{"text": " \n"}]},
],
Expand Down
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