# LangChainTracer

> **Class** in `@langchain/core`

📖 [View in docs](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer)

Interface for the input parameters of the BaseCallbackHandler class. It
allows to specify which types of events should be ignored by the
callback handler.

## Signature

```javascript
class LangChainTracer
```

## Extends

- `BaseTracer`

## Implements

- `LangChainTracerFields`

## Constructors

- [`constructor()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/constructor)

## Properties

- `awaitHandlers`
- `client`
- `exampleId`
- `fields`
- `ignoreAgent`
- `ignoreChain`
- `ignoreCustomEvent`
- `ignoreLLM`
- `ignoreRetriever`
- `lc_kwargs`
- `lc_serializable`
- `name`
- `projectName`
- `raiseError`
- `replicas`
- `runMap`
- `runTreeMap`
- `tracingMetadata`
- `tracingTags`
- `usesRunTreeMap`
- `lc_aliases`
- `lc_attributes`
- `lc_id`
- `lc_namespace`
- `lc_secrets`
- `lc_serializable_keys`

## Methods

- [`_addChildRun()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/_addChildRun)
- [`_addRunToRunMap()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/_addRunToRunMap)
- [`_createRunForChainStart()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/_createRunForChainStart)
- [`_createRunForChatModelStart()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/_createRunForChatModelStart)
- [`_createRunForLLMStart()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/_createRunForLLMStart)
- [`_createRunForRetrieverStart()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/_createRunForRetrieverStart)
- [`_createRunForToolStart()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/_createRunForToolStart)
- [`_endTrace()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/_endTrace)
- [`_getExecutionOrder()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/_getExecutionOrder)
- [`copy()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/copy)
- [`copyWithTracingConfig()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/copyWithTracingConfig)
- [`getRun()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/getRun)
- [`getRunById()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/getRunById)
- [`getRunTreeWithTracingConfig()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/getRunTreeWithTracingConfig)
- [`handleAgentAction()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleAgentAction)
- [`handleAgentEnd()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleAgentEnd)
- [`handleChainEnd()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleChainEnd)
- [`handleChainError()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleChainError)
- [`handleChainStart()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleChainStart)
- [`handleChatModelStart()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleChatModelStart)
- [`handleChatModelStreamEvent()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleChatModelStreamEvent)
- [`handleCustomEvent()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleCustomEvent)
- [`handleLLMEnd()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleLLMEnd)
- [`handleLLMError()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleLLMError)
- [`handleLLMNewToken()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleLLMNewToken)
- [`handleLLMStart()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleLLMStart)
- [`handleRetrieverEnd()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleRetrieverEnd)
- [`handleRetrieverError()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleRetrieverError)
- [`handleRetrieverStart()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleRetrieverStart)
- [`handleText()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleText)
- [`handleToolEnd()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleToolEnd)
- [`handleToolError()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleToolError)
- [`handleToolEvent()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleToolEvent)
- [`handleToolStart()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/handleToolStart)
- [`onAgentAction()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onAgentAction)
- [`onAgentEnd()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onAgentEnd)
- [`onChainEnd()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onChainEnd)
- [`onChainError()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onChainError)
- [`onChainStart()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onChainStart)
- [`onLLMEnd()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onLLMEnd)
- [`onLLMError()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onLLMError)
- [`onLLMNewToken()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onLLMNewToken)
- [`onLLMStart()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onLLMStart)
- [`onRetrieverEnd()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onRetrieverEnd)
- [`onRetrieverError()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onRetrieverError)
- [`onRetrieverStart()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onRetrieverStart)
- [`onRunCreate()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onRunCreate)
- [`onRunUpdate()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onRunUpdate)
- [`onText()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onText)
- [`onToolEnd()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onToolEnd)
- [`onToolError()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onToolError)
- [`onToolStart()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/onToolStart)
- [`persistRun()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/persistRun)
- [`stringifyError()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/stringifyError)
- [`toJSON()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/toJSON)
- [`toJSONNotImplemented()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/toJSONNotImplemented)
- [`updateFromRunTree()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/updateFromRunTree)
- [`[hasInstance]()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/[hasInstance])
- [`fromMethods()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/fromMethods)
- [`getTraceableRunTree()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/getTraceableRunTree)
- [`lc_name()`](https://reference.langchain.com/javascript/langchain-core/tracers/tracer_langchain/LangChainTracer/lc_name)

---

[View source on GitHub](https://github.com/langchain-ai/langchainjs/blob/cc39f564a9df18655ee4ae92de3f32e251021db8/libs/langchain-core/src/tracers/tracer_langchain.ts#L89)