LangChain Webhooks and Event Dispatch (Python) Overview A team wires per-tool webhook dispatch from their LangChain agent via FastAPI — analytics is always N seconds late because fire after the HTTP response closes, not during the stream (P60). Worse: the they attached via fires on the outer agent but is dark on the subagent's tool calls — custom callbacks are not inherited by LangGraph subgraphs (P28), they must be passed via at invoke time. Pain-catalog anchors handled here: - P28 — Callbacks via don't propagate to subgraphs - P46 — SSE streams dropped by buffering proxies (see ) - P47 — em…