@skein-js/langgraph

The LangGraph.js binding for @skein-js/agent-protocol — presents a compiled graph as the engine's AgentGraph.

Part of skein-js — the open-source alternative to LangGraph Platform for TypeScript: a self-hosted Agent Protocol server for LangGraph.js, and a drop-in replacement for the LangGraph CLI.

Status: 🚧 Pre-alpha — implemented.

Why this package exists

@skein-js/agent-protocol drives an AgentGraph: a structural type naming only what the engine calls (stream and getState required; getStateHistory, updateState, bulkUpdateState, streamEvents, invoke, getGraphAsync, getSubgraphsAsync optional). A LangGraph.js CompiledGraph satisfies that type already — but three things the engine used to do are LangGraph-specific, and each was a value import of @langchain/langgraph:

| What | Now | | ------------------------------------------------------------- | ------------------------------------------------------------------------------------ | | Building a Command to resume an interrupted run | The engine emits a branded envelope (agentCommand); langGraphAgent translates it | | Bridging long-term memory into a BaseStore for getStore() | SkeinBaseStore, injected as ProtocolDeps.storeBridge | | Cloning a checkpoint when re-putting it under a new thread id | cloneLangGraphCheckpoint, injected as ProtocolDeps.cloneCheckpoint |

Moving them here is what lets npm i @skein-js/agent-protocol pull no graph runtime — asserted on the built entry by static-imports.test.ts, not merely documented.

This package depends on @skein-js/agent-protocol, never the reverse, and imports only its public entry point. If it ever needs an internal, the internal is missing from the public API.

You probably do not import this directly

Every on-ramp wires it for you — skein dev/start, buildRuntime, embedInMemoryGraphs, embedPostgresGraphs. Reach for it when you assemble ProtocolDeps by hand.

import { createExpressServer } from "@skein-js/express";
import { cloneLangGraphCheckpoint, langGraphResolver, SkeinBaseStore } from "@skein-js/langgraph";
import { MemorySaver } from "@langchain/langgraph";

const deps = {
  store,
  queue,
  bus,
  checkpointer: new MemorySaver(),
  // Wrap the resolver so compiled graphs are presented as `AgentGraph`s.
  graphs: langGraphResolver(myResolver),
  // The three runtime-specific constructors the engine injects rather than imports.
  storeBridge: (repo) => new SkeinBaseStore(repo),
  ephemeralCheckpointer: () => new MemorySaver(),
  cloneCheckpoint: cloneLangGraphCheckpoint,
};

await createExpressServer({ deps }).listen(2024);

API

• langGraphResolver(resolver) — a GraphResolver whose graphs are wrapped with langGraphAgent. Memoized per underlying graph, so load() stays identity-stable.
• langGraphAgent(compiled) — presents one compiled graph as an AgentGraph, translating command envelopes on stream / streamEvents / invoke / bulkUpdateState. Overrides live on a prototype clone and delegate with this, so the per-call checkpointer the engine attaches afterwards is still honoured.
• SkeinBaseStore — bridges a skein StoreRepo into a LangGraph BaseStore, so graph nodes reach long-term cross-thread memory via getStore(). The exact inverse of fromBaseStore, which stays in @skein-js/agent-protocol because its BaseStore import is type-only.
• cloneLangGraphCheckpoint(checkpoint) — delegates to LangGraph's own copyCheckpoint. Deliberately not reimplemented: it knows which fields are safe to share.

Reuse

Everything here is a thin adapter over @langchain/langgraph — Command, BaseStore, copyCheckpoint, MemorySaver. Nothing is reimplemented; see docs/reuse.md.

License

Apache-2.0