isStreamChannel

@langchain/langgraph/stream — backend toolkit for the v2 streaming protocol.

This entrypoint collects the primitives needed to build a custom transport or server on top of the Agent Streaming Protocol:

• StreamChannel — an append-only, buffered event log with independent replay cursors, for buffering events and fanning them out to multiple subscribers.
• convertToProtocolEvent — turns raw streamEvents (v3) payloads into canonical ProtocolEvents.
• inferChannel / matchesSubscription — map an event to its Channel and decide whether a buffered event should be delivered for a given subscription filter (with optional since replay cursor).
• SUPPORTED_CHANNELS / isSupportedChannel — the recognized channel set and a guard for validating subscription requests.

These are intentionally transport-agnostic: pair them with SSE, WebSocket, or any custom framing to expose a graph over the protocol.