# LangSmithExporter

Sends Tracing data to LangSmith for observability.

## Constructor

```typescript
new LangSmithExporter(config: LangSmithExporterConfig)
```

## LangSmithExporterConfig

```typescript
interface LangSmithExporterConfig extends ClientConfig, BaseExporterConfig {
  client?: Client;
  projectName?: string;
}
```

Extends both `ClientConfig` (from LangSmith SDK) and `BaseExporterConfig`:

- From `BaseExporterConfig`: `logger?: IMastraLogger`, `logLevel?: LogLevel | 'debug' | 'info' | 'warn' | 'error'`
- From `ClientConfig`: `apiKey`, `apiUrl`, `callerOptions`, `hideInputs`, `hideOutputs`, etc.

## Methods

### exportTracingEvent

```typescript
async exportTracingEvent(event: TracingEvent): Promise<void>
```

Exports a tracing event to LangSmith.

### flush

```typescript
async flush(): Promise<void>
```

Force flushes any pending spans to LangSmith without shutting down the exporter. Useful in serverless environments where you need to ensure spans are exported before the runtime terminates.

### shutdown

```typescript
async shutdown(): Promise<void>
```

Ends all active spans and clears the trace map.

## Usage

```typescript
import { LangSmithExporter } from "@mastra/langsmith";

const exporter = new LangSmithExporter({
  apiKey: process.env.LANGSMITH_API_KEY,
  projectName: "my-project", // Optional: specify which project to send traces to
  apiUrl: "https://api.smith.langchain.com",
  logLevel: "info",
});
```

## Environment Variables

| Variable             | Description                                                           |
| -------------------- | --------------------------------------------------------------------- |
| `LANGSMITH_API_KEY`  | Your LangSmith API key                                                |
| `LANGCHAIN_PROJECT`  | Default project name for traces (used if `projectName` not specified) |
| `LANGSMITH_BASE_URL` | API URL for self-hosted instances                                     |

## Span Type Mapping

| Span Type          | LangSmith Type |
| ------------------ | -------------- |
| `MODEL_GENERATION` | `llm`          |
| `MODEL_CHUNK`      | `llm`          |
| `TOOL_CALL`        | `tool`         |
| `MCP_TOOL_CALL`    | `tool`         |
| All others         | `chain`        |