agentmetrics-langchain (JS/TS)

AgentMetrics integration for LangChain.js. Pass one callback to any chain or agent .invoke() call and every run reports back to your dashboard showing latency, cost, token counts, tool calls, and errors, with no changes to your agent logic.

Install

npm install agentmetrics-langchain

Quickstart

import { AgentMetricsCallback } from "agentmetrics-langchain";

const cb = new AgentMetricsCallback({
  agentId: "my-langchain-agent",
  baseUrl: "http://localhost:8099",
});

const result = await agent.invoke(
  { input: "What is the weather in Paris?" },
  { callbacks: [cb] },
);

API

new AgentMetricsCallback(opts)

| Option | Default | Description | |---|---|---| | agentId | "langchain-agent" | Label shown in the dashboard | | baseUrl | "http://localhost:8099" | AgentMetrics server address |

Pass the callback via the callbacks array in the second argument to .invoke(). It implements BaseCallbackHandler from @langchain/core and tracks the top-level chain only, with all nested sub-chains aggregated into the same run.

Supports both OpenAI (usage_metadata) and Anthropic (input_token_details) token counting paths.

What gets tracked

Each top-level chain invocation emits one event to /v1/events on completion or error:

| Field | Description | |---|---| | status | success or failed | | duration_ms | Wall-clock chain duration | | input_tokens / output_tokens | Aggregated across all LLM calls | | cache_read_tokens / cache_write_tokens | Cache token counts (Anthropic) | | llm_calls | Number of LLM requests in the chain | | tool_calls / tool_errors | Tool usage counts | | tool_names | Array of tools invoked | | model | Model name from the first LLM call | | estimated_cost_usd | Computed from token counts and model pricing | | error | First 500 chars of the error message on failure |

LangGraph.js

Works with LangGraph.js the same way:

import { AgentMetricsCallback } from "agentmetrics-langchain";

const cb  = new AgentMetricsCallback({ baseUrl: "http://localhost:8099" });
const app = buildGraph().compile();

const result = await app.invoke(state, { callbacks: [cb] });

License

MIT