Question

A Generative AI Engineer is building a customer-facing chat assistant on Databricks using LangChain Expression Language (LCEL). The frontend team requires that partial responses appear token-by-token in the UI as the foundation model generates them, rather than waiting for the full completion. The chain is composed as: prompt | chat_model | StrOutputParser(). Which approach correctly enables incremental token delivery from this LCEL chain?

Accepted Answer

Invoke the chain with chain.stream(input) and iterate over the yielded chunks, forwarding each to the UI as it arrives

Answer

Call chain.invoke(input) inside a loop and send the accumulated string on each iteration

Answer

Wrap the chain with chain.batch([input]) so multiple partial results are returned as a list

Answer

Set the StrOutputParser to async mode and call chain.ainvoke(input) to receive tokens as they complete