ai-agents-streaming-error-hand-keyerror-for-the-configured-output-key-e-g-answer--0dfb6b6f

THEN Ensure robust access to streamed chunks by using .get() with a fallback; upgrade langchain-core to the latest version if possible, as this is a known callback tracer issue in versions ≤0.2.23. For a quick workaround, wrap the stream loop in a try-except for KeyError to suppress the log noise.

for chunk in chain.stream(input, config):
    answer = chunk.get("answer")
    if answer is not None:
        print(answer, end="")