> ## Documentation Index
> Fetch the complete documentation index at: https://docs.trynexus.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Nexus

> AI monitoring for custom silent failure modes in production

**Nexus** helps you trace AI execution in three ways:

* **Automatic tracing** via a LangChain callback handler.
* **OpenAI Agents SDK tracing** via `NexusOpenAITracingProcessor`.
* **Manual tracing** via `NexusClient` spans in your own code.

You can log runs, connect parent and child operations, and inspect tree structures from stored traces.

## Start here

<CardGroup cols={2}>
  <Card title="Quickstart" icon="rocket" href="/quickstart">
    Install the package and send your first trace.
  </Card>

  <Card title="LangChain integration" icon="brain" href="/guides/langchain">
    Attach `LangHandler` to chains, tools, and agents.
  </Card>

  <Card title="OpenAI Agents SDK" icon="robot" href="/guides/openai">
    Trace OpenAI agents with `NexusOpenAITracingProcessor`.
  </Card>

  <Card title="Configuration" icon="sliders" href="/guides/configuration">
    Configure DB and trigger behavior for your environment.
  </Card>
</CardGroup>

## What Nexus captures

* `run_id`, `trace_id`, `parent_run_id`, and `user_id`
* event category (`chain`, `llm`, `tool`, `agent`, `retriever`, and more)
* name metadata (for model, chain, tool, and agent nodes)
* JSON payloads for `input`, `output`, and `error`

This structure lets you reconstruct execution trees after a run and debug both failed and successful paths.

## Choose your tracing path

<CardGroup cols={2}>
  <Card title="I use LangChain" icon="wand-magic-sparkles" href="/guides/langchain">
    Plug in a callback and collect traces with minimal code changes.
  </Card>

  <Card title="I use OpenAI Agents SDK" icon="robot" href="/guides/openai">
    Register a trace processor and capture every agent span automatically.
  </Card>

  <Card title="I need full control" icon="route" href="/guides/manual-tracing">
    Add spans exactly where your app does meaningful work.
  </Card>
</CardGroup>

<Tip>
  Your Nexus API key (`nexus_api_key`) is available on the [Nexus platform](https://app.trynexus.io).
</Tip>