Stroutputparser

Recap: On Day 6, LangBot gained output parsers and now responds in two modes — chat mode returns typed LangBotResponse objects with mood and confidence, and list mode returns clean list[str] via CommaSeparatedListOutputParser. Both modes use .invoke(), which means the entire response arrives at once after the model finishes generating. Today we fix that — LangBot learns to type its replies one token at a time.

The problem: waiting for the whole answer

Every interaction so far has the same rhythm:

Recap: On Day 5, LangBot started returning typed objects — every response is now a LangBotResponse with .message, .mood, and .confidence. That is great when you need structured metadata. But structured output is not always the right tool. Sometimes you just want a clean string. Sometimes you want a parsed list. Today we add output parsers — lightweight LCEL components that transform raw AIMessage output into exactly the shape you need.