We're open-sourcing Lightrace

Why we're open-sourcing it

Lightrace is not a side project we decided to publish. It is the observability layer we run our own desk on: every autonomous agent run, every tool call, every model generation, and every failure on our platform is recorded through it. We built it because nothing off the shelf answered the question we ask most often when an agent misbehaves — what exactly broke, and who is fixing it?

That question shaped the product. A trace alone tells you what happened; it does not tell you what to do. So we treated error and issue handling as a first-class part of tracing: any observation that ends in an error is captured with its stacktrace, fingerprinted, grouped into a single issue, prioritized, and queued for triage — right next to the trace that produced it.

Traces tell you what happened. Issues tell you what broke.

We are releasing Lightrace under Apache 2.0 because the infrastructure we depend on was built the same way. Kafka, Airflow, Jaeger, and Sentry all began as internal tools that solved a real problem at one company, and every agent team deserves the same option today: tracing and error tracking you can read, audit, and self-host.

What Lightrace does

• Agent tracing & observe — a hierarchical trace viewer for every run — model calls, tools, chains, and spans — with token usage, latency, and cost broken down per step.

• Error tracking & issue grouping — every failed observation becomes a grouped issue you can triage, assign, and resolve, with the stacktrace and context kept next to the trace that produced it.

• Remote tool invocation Beta — mark a tool as trace(type="tool") and re-run it from the dashboard — against the exact inputs that failed, without reproducing the run by hand.

• Real-time updates — live trace streaming over WebSocket, so you watch agent runs as they happen instead of polling for results.

• Tools page — see every connected SDK instance, the tools it registered, and their schemas — a live map of what your agents can actually do.

• Multi-project RBAC — owner, Admin, Member, and Viewer roles per project, with API key creation and rotation built in.

Error tracking, built for agents

Every failed tool, model call, or span becomes an issue you can triage and fix — not a log line buried in a waterfall. It is the part of Lightrace we depend on most, and the reason we built it.

Python and TypeScript SDKs

Instrument an agent in a few lines. Errors are captured automatically as level: ERROR observations, with statusMessage and stacktrace attached.

pip install lightrace

from lightrace import Lightrace, trace

lt = Lightrace(public_key="pk-lt-demo", secret_key="sk-lt-demo")

@trace()
def run_agent(query: str):
    return search(query)

@trace(type="tool")  # remotely invocable from the UI
def search(query: str) -> list:
    return ["result"]

run_agent("hello")
lt.flush()

npm install lightrace

import { LightRace, trace } from "lightrace";

const lt = new LightRace({
  publicKey: "pk-lt-demo",
  secretKey: "sk-lt-demo",
});

const search = trace("search", { type: "tool" }, async (q: string) => {
  return ["result"];
});

const runAgent = trace("run-agent", async (q: string) => search(q));

await runAgent("hello");
lt.flush();

Integrations are available for LangChain, the Claude Agent SDK, OpenAI, and Anthropic. See the Python SDK and TypeScript SDK docs for the full list.

Drop-in Langfuse compatibility

Already using Langfuse SDKs? Point them at a Lightrace instance — both the v3 JSON batch ingestion API and the v4 OpenTelemetry (OTLP) endpoint are supported.

export LANGFUSE_PUBLIC_KEY=pk-lt-demo
export LANGFUSE_SECRET_KEY=sk-lt-demo
export LANGFUSE_HOST=http://localhost:3000

How Lightrace compares

Where Lightrace sits against the tools it is most often compared with.

* Sentry is source-available under the Business Source License, not an OSI-approved open-source license.

Frequently asked questions

Run it on your own infrastructure

Lightrace is Apache 2.0 and free to self-host. Star the repo, run it locally, and tell us what breaks.

Related repos: Python SDK · TypeScript SDK · CLI