LangChain.js

LangChain.js is the JavaScript/TypeScript port of LangChain — a framework for composing LLM calls, tools, and retrieval into chains and agents. Arize AX captures every chain, prompt, tool call, and LLM call by manually instrumenting the @langchain/core/callbacks/manager module via the @arizeai/openinference-instrumentation-langchain package.

Prerequisites

Node.js 18+
An Arize AX account (sign up)
An OPENAI_API_KEY from the OpenAI Platform

Launch Arize AX

Sign in to your Arize AX account.
From Space Settings, copy your Space ID and API Key. You will set them as ARIZE_SPACE_ID and ARIZE_API_KEY below.

Install

npm install @langchain/core @langchain/openai \
  @arizeai/openinference-instrumentation-langchain \
  @arizeai/openinference-semantic-conventions \
  @opentelemetry/api \
  @opentelemetry/exporter-trace-otlp-proto \
  @opentelemetry/instrumentation \
  @opentelemetry/resources \
  @opentelemetry/sdk-trace-base \
  @opentelemetry/sdk-trace-node \
  @opentelemetry/semantic-conventions

Configure credentials

export ARIZE_SPACE_ID="<your-space-id>"
export ARIZE_API_KEY="<your-api-key>"
export ARIZE_PROJECT_NAME="langchain-js-tracing-example"
export OPENAI_API_KEY="<your-openai-api-key>"

Setup tracing

// instrumentation.ts
import { OTLPTraceExporter } from "@opentelemetry/exporter-trace-otlp-proto";
import { resourceFromAttributes } from "@opentelemetry/resources";
import { SimpleSpanProcessor } from "@opentelemetry/sdk-trace-base";
import { NodeTracerProvider } from "@opentelemetry/sdk-trace-node";
import { ATTR_SERVICE_NAME } from "@opentelemetry/semantic-conventions";
import {
  SEMRESATTRS_PROJECT_NAME,
} from "@arizeai/openinference-semantic-conventions";
import {
  LangChainInstrumentation,
} from "@arizeai/openinference-instrumentation-langchain";
import * as CallbackManagerModule from "@langchain/core/callbacks/manager";

const projectName =
  process.env.ARIZE_PROJECT_NAME ?? "langchain-js-tracing-example";

export const provider = new NodeTracerProvider({
  resource: resourceFromAttributes({
    [ATTR_SERVICE_NAME]: projectName,
    [SEMRESATTRS_PROJECT_NAME]: projectName,
  }),
  spanProcessors: [
    new SimpleSpanProcessor(
      new OTLPTraceExporter({
        url: "https://otlp.arize.com/v1/traces",
        headers: {
          "arize-space-id": process.env.ARIZE_SPACE_ID ?? "",
          "arize-api-key": process.env.ARIZE_API_KEY ?? "",
        },
      }),
    ),
  ],
});

provider.register();

const instrumentation = new LangChainInstrumentation();
instrumentation.manuallyInstrument(CallbackManagerModule);

console.log("Arize AX tracing initialized for LangChain.js.");

Run LangChain.js

// example.ts

// Importing instrumentation first ensures tracing is set up before any
// LangChain client is created.
import { provider } from "./instrumentation";

import { ChatOpenAI } from "@langchain/openai";
import { ChatPromptTemplate } from "@langchain/core/prompts";
import { StringOutputParser } from "@langchain/core/output_parsers";
import { awaitAllCallbacks } from "@langchain/core/callbacks/promises";

// ChatOpenAI reads OPENAI_API_KEY from the environment.
const model = new ChatOpenAI({ model: "gpt-5.5" });
const prompt = ChatPromptTemplate.fromTemplate(
  "Answer the question concisely.\nQuestion: {question}\nAnswer:",
);
const chain = prompt.pipe(model).pipe(new StringOutputParser());

const result = await chain.invoke({
  question: "Why is the ocean salty? Answer in two sentences.",
});

console.log(result);

// LangChain.js dispatches tracing callbacks in the background, so the
// root chain span's `onEnd` can fire *after* `invoke()` resolves. Drain
// the callback queue before flushing, otherwise a batching span processor
// races the trailing root span and drops it. See the Span filter section.
await awaitAllCallbacks();

// Flush any pending spans before the process exits.
await provider.forceFlush();

Expected output

Arize AX tracing initialized for LangChain.js.
The ocean is salty because rivers continuously dissolve mineral salts from rocks and soil and carry them to the sea, where they accumulate over millions of years. Water leaves the ocean through evaporation but the salts remain, steadily concentrating until reaching today's roughly 3.5% salinity.

Verify in Arize AX

Open your Arize AX space and select project langchain-js-tracing-example.
You should see a new trace within ~30 seconds containing a RunnableSequence parent span (CHAIN) wrapping ChatPromptTemplate (CHAIN), ChatOpenAI (LLM, model gpt-5.5), and StrOutputParser (CHAIN) child spans, with the prompt, response, and token usage attached to the LLM span.
If no traces appear, see Troubleshooting.

Check from the skill, CLI, or SDK

Confirm spans are actually reaching your Arize AX project. Use whichever fits your workflow — the skill and CLI work for any framework; the SDK check is shown for each language.

Arize skill (agent)
AX CLI
SDK

Install the Arize Skills plugin and let your coding agent check for you:

npx skills add Arize-ai/arize-skills

Then prompt your agent:

Use the arize-trace skill to export and analyze recent traces from my project. Confirm spans are arriving, and summarize any errors or latency issues.

Export recent spans for your project — any rows mean traces are landing:

ax spans export "$ARIZE_PROJECT_NAME" --space "$ARIZE_SPACE_ID" \
  --limit 5 --stdout | jq 'length'

A non-zero count confirms spans reached Arize AX. Run ax auth login first if you have not authenticated. See the ax spans reference.

Query the project’s spans and check that at least one came back.

import os
from arize import ArizeClient

client = ArizeClient(api_key=os.environ["ARIZE_API_KEY"])
resp = client.spans.list(
    project=os.environ["ARIZE_PROJECT_NAME"],
    space=os.environ["ARIZE_SPACE_ID"],
    limit=5,
)
count = len(resp.spans)
print(
    f"{count} span(s) found" if count else "No spans yet — recheck setup"
)

// Reads ARIZE_API_KEY from the environment.
import { listSpans } from "@arizeai/ax-client";

const { data: spans } = await listSpans({
  project: process.env.ARIZE_PROJECT_NAME!,
  space: process.env.ARIZE_SPACE_ID!,
  limit: 5,
});
const count = spans.length;
console.log(
  count ? `${count} span(s) found` : "No spans yet — recheck setup",
);

client, err := arize.NewClient(
    arize.Config{APIKey: os.Getenv("ARIZE_API_KEY")},
)
if err != nil {
    log.Fatal(err)
}
resp, err := client.Spans.List(ctx, spans.ListRequest{
    Project: os.Getenv("ARIZE_PROJECT_NAME"),
    Space:   os.Getenv("ARIZE_SPACE_ID"),
    Limit:   5,
})
if err != nil {
    log.Fatal(err)
}
fmt.Printf("%d span(s) found\n", len(resp.Spans))

SDK span references: Python · TypeScript · Go.

Span filter

The basic setup above exports every span the tracer provider receives. When LangChain runs alongside other instrumentations (@opentelemetry/instrumentation-http, Next.js’s built-in tracing, framework HTTP middleware), those instrumentations emit POST / GET spans for every fetch, and the LangChain spans nest under those HTTP roots. OpenInference-tagged spans carry an openinference.span.kind attribute that the LangChain instrumentor sets — checking for it is enough to drop non-OpenInference spans. Swap SimpleSpanProcessor in instrumentation.ts for a filtering subclass:

import {
  ReadableSpan,
  SimpleSpanProcessor,
} from "@opentelemetry/sdk-trace-base";
import { SemanticConventions } from "@arizeai/openinference-semantic-conventions";

function isOpenInferenceSpan(span: ReadableSpan): boolean {
  return (
    typeof span.attributes[SemanticConventions.OPENINFERENCE_SPAN_KIND] ===
    "string"
  );
}

class OpenInferenceFilteringSpanProcessor extends SimpleSpanProcessor {
  onEnd(span: ReadableSpan): void {
    if (!isOpenInferenceSpan(span)) return;
    super.onEnd(span);
  }
}

// then in spanProcessors:
new OpenInferenceFilteringSpanProcessor(
  new OTLPTraceExporter({ /* ... */ }),
);

The trade-off: filtering removes the HTTP root spans, which orphans the surviving LangChain spans on the Traces tab (no parent to anchor them) — they remain visible on the Spans tab. If you also need a clean trace tree on the Traces tab, swap the filter for a span processor that promotes the first LangChain span to root by clearing its parent ID:

// root-aware-processor.ts
import { Context } from "@opentelemetry/api";
import {
  BatchSpanProcessor,
  ReadableSpan,
  Span,
  SpanExporter,
} from "@opentelemetry/sdk-trace-base";
import { getSession } from "@arizeai/openinference-core";
import {
  SemanticConventions,
  SESSION_ID,
} from "@arizeai/openinference-semantic-conventions";
import { LRUCache } from "lru-cache";

// Top-level LangChain / LangGraph runnable names. `LangGraph` is the
// `lc_name()` of a compiled Pregel graph (returned by `createReactAgent`
// and friends), `RunnableSequence` is the typical chain root for
// `prompt.pipe(model).pipe(parser)`-style chains, and `AgentExecutor`
// covers legacy LangChain agents. Match on the first whitespace-delimited
// token so suffixed run names (e.g. `RunnableSequence my-chain`) still hit.
const ROOT_OI_SPAN_PREFIXES = [
  "LangGraph",
  "RunnableSequence",
  "AgentExecutor",
];

function isRootOISpanByName(spanName: string): boolean {
  const head = spanName.split(" ")[0];
  return ROOT_OI_SPAN_PREFIXES.some(
    (prefix) => head === prefix || head.startsWith(prefix + " "),
  );
}

function isOpenInferenceSpan(span: ReadableSpan): boolean {
  return (
    typeof span.attributes[SemanticConventions.OPENINFERENCE_SPAN_KIND] ===
    "string"
  );
}

interface RootAwareConfig {
  exporter: SpanExporter;
  /** LRU size for tracking which traces have a promoted root. */
  cacheSize?: number;
}

/**
 * Filters non-OpenInference spans (HTTP, fetch, etc.) and promotes the
 * first LangChain span in each trace to root by clearing its parent IDs.
 * Also propagates session ids from context onto every emitted span.
 */
export class RootAwareOpenInferenceProcessor extends BatchSpanProcessor {
  private traceIds: LRUCache<string, boolean>;

  constructor(config: RootAwareConfig) {
    super(config.exporter);
    this.traceIds = new LRUCache({ max: config.cacheSize ?? 1000 });
  }

  onStart(span: Span, parentContext: Context): void {
    const session = getSession(parentContext);
    if (session?.sessionId) {
      span.setAttribute(SESSION_ID, session.sessionId);
    }

    const traceId = span.spanContext().traceId;
    if (
      isRootOISpanByName(span.name) &&
      !this.traceIds.has(traceId)
    ) {
      // parentSpanId is readonly on the public Span type; cast to clear.
      (span as unknown as { parentSpanId?: string }).parentSpanId =
        undefined;
      (span as unknown as { parentSpanContext?: unknown })
        .parentSpanContext = undefined;
      this.traceIds.set(traceId, true);
    }

    super.onStart(span, parentContext);
  }

  onEnd(span: ReadableSpan): void {
    if (!isOpenInferenceSpan(span)) return;
    super.onEnd(span);
  }

  shutdown(): Promise<void> {
    this.traceIds.clear();
    return super.shutdown();
  }
}

Wire it in by replacing the OpenInferenceFilteringSpanProcessor in instrumentation.ts:

import { RootAwareOpenInferenceProcessor } from "./root-aware-processor";

spanProcessors: [
  new RootAwareOpenInferenceProcessor({
    exporter: new OTLPTraceExporter({
      url: "https://otlp.arize.com/v1/traces",
      headers: {
        "arize-space-id": process.env.ARIZE_SPACE_ID ?? "",
        "arize-api-key": process.env.ARIZE_API_KEY ?? "",
      },
    }),
  }),
],

The recipe needs two additional dependencies: npm install @arizeai/openinference-core lru-cache.

Troubleshooting

No traces in Arize AX. Confirm ARIZE_SPACE_ID and ARIZE_API_KEY are set in the same shell that runs example.ts. Enable OpenTelemetry debug logs with export OTEL_LOG_LEVEL=debug and re-run.
LangChain spans missing but other spans present. instrumentation.manuallyInstrument(CallbackManagerModule) must run before any code creates a LangChain client. Make sure import { provider } from "./instrumentation" (or a side-effect-only import "./instrumentation") is the first import in your entry point.
401 from OpenAI. Verify OPENAI_API_KEY is set and has access to gpt-5.5. Swap for a model your key can call.
Process exits before spans flush. Spans are exported asynchronously; always await provider.forceFlush() (or provider.shutdown()) before the process exits to avoid losing trailing spans.
Root chain span missing with a batching processor. LangChain.js runs tracing callbacks in the background by default, so the outer chain span’s onEnd can fire after chain.invoke() resolves. A BatchSpanProcessor (including the RootAwareOpenInferenceProcessor recipe) then races a bare forceFlush() and drops that trailing root span, orphaning its children. Call await awaitAllCallbacks() (from @langchain/core/callbacks/promises) before flushing, or set LANGCHAIN_CALLBACKS_BACKGROUND=false. SimpleSpanProcessor hides the race because its per-span export keeps the event loop alive.
LangChain spans orphaned on the Traces tab. Expected when isOpenInferenceSpan is the only filter — see Span filter above for the RootAwareOpenInferenceProcessor recipe that promotes the first LangChain span to root.

Version compatibility

Instrumentation >=1.0.0 supports both attribute masking and context attribute propagation. The matrix below tracks instrumentor support across LangChain core releases:

Instrumentation Version	LangChain ^0.3.0	LangChain ^0.2.0	LangChain ^0.1.0
`>=1.0.0`	Yes	Yes	Yes
`>=0.2.0`	No	Yes	Yes
`>=0.1.0`	No	No	Yes

OpenTelemetry

LLM Providers

Agent Frameworks

Coding Agents

Platforms

Orchestration

Evaluation

Prerequisites

Launch Arize AX

Install

Configure credentials

Setup tracing

Run LangChain.js

Expected output

Verify in Arize AX

Check from the skill, CLI, or SDK

Span filter

Troubleshooting

Version compatibility

Resources

LangChain.js Documentation

OpenInference LangChain Instrumentor (JS/TS)

LangChain.js GitHub

​Prerequisites

​Launch Arize AX

​Install

​Configure credentials

​Setup tracing

​Run LangChain.js

​Expected output

​Verify in Arize AX

​Check from the skill, CLI, or SDK

​Span filter

​Troubleshooting

​Version compatibility

​Resources

LangChain.js Documentation

OpenInference LangChain Instrumentor (JS/TS)

LangChain.js GitHub

Prerequisites

Launch Arize AX

Install

Configure credentials

Setup tracing

Run LangChain.js

Expected output

Verify in Arize AX

Check from the skill, CLI, or SDK

Span filter

Troubleshooting

Version compatibility

Resources