@skein-js/langsmith

LangSmith tracing for skein-js — run identity and thread grouping on every graph call.

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.

What's here

LangSmith's tracer already instruments everything inside your graph — every LLM call, tool, and chain. What it can't know on its own is what a "run" is on your server, so without help every run lands in LangSmith as an anonymous root trace: no thread, no assistant, no user.

This package supplies that identity. Above all it sets session_id, the key LangSmith's Threads view groups on — so a conversation reads as one thread in LangSmith exactly as it does through the Agent Protocol.

It deliberately does not attach a tracer of its own. @langchain/core already installs a global tracer when LANGSMITH_TRACING is on; adding a second would send every span twice — you'd pay double and couldn't trust the numbers. Instead this sink makes sure that one tracer is switched on and properly configured, then enriches what it sends.

Install

pnpm add @skein-js/langsmith langsmith

langsmith and @langchain/core are optional peers — @langchain/core you already have via LangGraph.

Usage

Set LANGSMITH_API_KEY and you're done — the sink reads it, switches tracing on, and enriches every run:

import { createLangSmithTelemetry } from "@skein-js/langsmith";
import { embedInMemoryGraphs } from "@skein-js/server-kit";
import { createExpressServer } from "@skein-js/express";

const telemetry = createLangSmithTelemetry();
const server = await createExpressServer({
  deps: embedInMemoryGraphs({ agent }, { overrides: telemetry ? { telemetry } : {} }),
});

createLangSmithTelemetry() returns undefined when LangSmith isn't configured, so the ternary above is the whole "is it enabled" story.

Using the CLI? Don't write any of this — declare it in langgraph.json and skein dev / skein start wire it up:

{ "telemetry": { "langsmith": true } }

With LANGSMITH_API_KEY set, even that is optional: the adapter is auto-detected. See docs/observability.md.

What lands in LangSmith

| Where | What | | ---------- | ------------------------------------------------------------------------------------ | | metadata | session_id (= thread id), run_id, thread_id, assistant_id, graph_id | | metadata | ls_user_id when auth is configured, skein_trigger (wait/stream/background) | | tags | skein, graph:<id>, trigger:<how>, assistant:<id> | | Run name | the graph id |

API

• createLangSmithTelemetry(options?): TelemetrySink | undefined — returns undefined when LangSmith is not configured (no API key and no explicit projectName), so the result can be passed straight through.
  • apiKey — defaults to LANGSMITH_API_KEY / LANGCHAIN_API_KEY
  • projectName — defaults to LANGSMITH_PROJECT / LANGCHAIN_PROJECT
  • endpoint — defaults to LANGSMITH_ENDPOINT, for self-hosted LangSmith
  • enableTracing — whether to switch the global tracer on when it isn't already (default true). Existing environment values are never overwritten, so a deliberate LANGSMITH_TRACING=false is respected.
  • env — the environment to read and write; defaults to process.env.

Learn more

• Observability — traces, metrics, and writing your own sink
• Errors & logging — the other two reporting surfaces
• skein-js overview

License

Apache-2.0