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

# MaximLangchainTracer

# Class: MaximLangchainTracer

Defined in: [src/lib/logger/langchain/tracer.ts:65](https://github.com/maximhq/maxim-js/blob/main/src/lib/logger/langchain/tracer.ts#L65)

LangChain callback handler for automatic observability with the Maxim platform.

Extends LangChain's BaseCallbackHandler to automatically trace and log
LangChain application executions including LLM calls, chains, tools, and
retrievers. Seamlessly integrates with existing LangChain applications
to provide comprehensive observability without code changes.

MaximLangchainTracer

## Example

```ts theme={null}
import { MaximLangchainTracer } from '@maximai/maxim-js';
import { ChatOpenAI } from '@langchain/openai';

// Basic setup
const maxim = new Maxim({ apiKey: 'your-api-key' });
const logger = await maxim.logger({ id: 'langchain-app' });
const tracer = new MaximLangchainTracer(logger);

// Use with LangChain models
const model = new ChatOpenAI({
  openAIApiKey: process.env.OPENAI_API_KEY,
  modelName: "gpt-4o-mini",
  callbacks: [tracer],
  metadata: {
    maxim: {
      generationName: "basic-openai-chat",
      generationTags: { testType: "basic", model: "openai" }
    },
  },
});

const response = await model.invoke("Hello world");
// Automatically logged to Maxim
```

## Extends

* `BaseCallbackHandler`

## Constructors

### Constructor

> **new MaximLangchainTracer**(`logger`, `input?`): `MaximLangchainTracer`

Defined in: [src/lib/logger/langchain/tracer.ts:87](https://github.com/maximhq/maxim-js/blob/main/src/lib/logger/langchain/tracer.ts#L87)

Creates a new MaximLangchainTracer instance.

#### Parameters

##### logger

[`MaximLogger`](../../core/classes/MaximLogger)

The Maxim logger instance to use for tracing

##### input?

`BaseCallbackHandlerInput`

Optional LangChain callback handler configuration

#### Returns

`MaximLangchainTracer`

#### Examples

```ts theme={null}
const maxim = new Maxim({ apiKey: 'your-api-key' });
const logger = await maxim.logger({ id: 'my-app' });
const tracer = new MaximLangchainTracer(logger);
```

```ts theme={null}
// With custom callback configuration
const tracer = new MaximLangchainTracer(logger, {
  ignoreLLM: false,
  ignoreChain: false,
  ignoreAgent: false
});
```

#### Overrides

`BaseCallbackHandler.constructor`

## Properties

### name

> `readonly` **name**: `"MaximLangchainTracer"` = `"MaximLangchainTracer"`

Defined in: [src/lib/logger/langchain/tracer.ts:66](https://github.com/maximhq/maxim-js/blob/main/src/lib/logger/langchain/tracer.ts#L66)

#### Overrides

`BaseCallbackHandler.name`

## Methods

### handleChainEnd()

> **handleChainEnd**(`outputs`, `runId`, `_parentRunId?`, `tags?`, `_kwargs?`): `void`

Defined in: [src/lib/logger/langchain/tracer.ts:226](https://github.com/maximhq/maxim-js/blob/main/src/lib/logger/langchain/tracer.ts#L226)

Called at the end of a Chain run, with the outputs and the run ID.

#### Parameters

##### outputs

`ChainValues`

##### runId

`string`

##### \_parentRunId?

`string`

##### tags?

`string`\[]

##### \_kwargs?

#### Returns

`void`

#### Overrides

`BaseCallbackHandler.handleChainEnd`

***

### handleChainError()

> **handleChainError**(`err`, `runId`, `_parentRunId?`, `tags?`): `void`

Defined in: [src/lib/logger/langchain/tracer.ts:252](https://github.com/maximhq/maxim-js/blob/main/src/lib/logger/langchain/tracer.ts#L252)

Called if a Chain run encounters an error

#### Parameters

##### err

`any`

##### runId

`string`

##### \_parentRunId?

`string`

##### tags?

`string`\[]

#### Returns

`void`

#### Overrides

`BaseCallbackHandler.handleChainError`

***

### handleChainStart()

> **handleChainStart**(`_chain`, `inputs`, `runId`, `parentRunId?`, `tags?`, `metadata?`, `_runType?`, `runName?`): `void`

Defined in: [src/lib/logger/langchain/tracer.ts:156](https://github.com/maximhq/maxim-js/blob/main/src/lib/logger/langchain/tracer.ts#L156)

Called at the start of a Chain run, with the chain name and inputs
and the run ID.

#### Parameters

##### \_chain

`Serialized`

##### inputs

`ChainValues`

##### runId

`string`

##### parentRunId?

`string`

##### tags?

`string`\[]

##### metadata?

`Record`\<`string`, `unknown`>

##### \_runType?

`string`

##### runName?

`string`

#### Returns

`void`

#### Overrides

`BaseCallbackHandler.handleChainStart`

***

### handleChatModelStart()

> **handleChatModelStart**(`llm`, `messages`, `runId`, `parentRunId?`, `extraParams?`, `tags?`, `metadata?`, `runName?`): `Promise`\<`void`>

Defined in: [src/lib/logger/langchain/tracer.ts:412](https://github.com/maximhq/maxim-js/blob/main/src/lib/logger/langchain/tracer.ts#L412)

Called at the start of a Chat Model run, with the prompt(s)
and the run ID.

#### Parameters

##### llm

`Serialized`

##### messages

`BaseMessage`\[]\[]

##### runId

`string`

##### parentRunId?

`string`

##### extraParams?

`Record`\<`string`, `unknown`>

##### tags?

`string`\[]

##### metadata?

`Record`\<`string`, `unknown`>

##### runName?

`string`

#### Returns

`Promise`\<`void`>

#### Overrides

`BaseCallbackHandler.handleChatModelStart`

***

### handleLLMEnd()

> **handleLLMEnd**(`output`, `runId`, `parentRunId?`, `tags?`): `void`

Defined in: [src/lib/logger/langchain/tracer.ts:353](https://github.com/maximhq/maxim-js/blob/main/src/lib/logger/langchain/tracer.ts#L353)

Called at the end of an LLM/ChatModel run, with the output and the run ID.

#### Parameters

##### output

`LLMResult`

##### runId

`string`

##### parentRunId?

`string`

##### tags?

`string`\[]

#### Returns

`void`

#### Overrides

`BaseCallbackHandler.handleLLMEnd`

***

### handleLLMError()

> **handleLLMError**(`err`, `runId`, `parentRunId?`, `tags?`): `void`

Defined in: [src/lib/logger/langchain/tracer.ts:383](https://github.com/maximhq/maxim-js/blob/main/src/lib/logger/langchain/tracer.ts#L383)

Called if an LLM/ChatModel run encounters an error

#### Parameters

##### err

`any`

##### runId

`string`

##### parentRunId?

`string`

##### tags?

`string`\[]

#### Returns

`void`

#### Overrides

`BaseCallbackHandler.handleLLMError`

***

### handleLLMStart()

> **handleLLMStart**(`llm`, `prompts`, `runId`, `parentRunId?`, `extraParams?`, `tags?`, `metadata?`, `name?`): `Promise`\<`void`>

Defined in: [src/lib/logger/langchain/tracer.ts:277](https://github.com/maximhq/maxim-js/blob/main/src/lib/logger/langchain/tracer.ts#L277)

Called at the start of an LLM or Chat Model run, with the prompt(s)
and the run ID.

#### Parameters

##### llm

`Serialized`

##### prompts

`string`\[]

##### runId

`string`

##### parentRunId?

`string`

##### extraParams?

`Record`\<`string`, `unknown`>

##### tags?

`string`\[]

##### metadata?

`Record`\<`string`, `unknown`>

##### name?

`string`

#### Returns

`Promise`\<`void`>

#### Overrides

`BaseCallbackHandler.handleLLMStart`

***

### handleRetrieverEnd()

> **handleRetrieverEnd**(`documents`, `runId`, `parentRunId?`, `tags?`): `void`

Defined in: [src/lib/logger/langchain/tracer.ts:534](https://github.com/maximhq/maxim-js/blob/main/src/lib/logger/langchain/tracer.ts#L534)

#### Parameters

##### documents

`DocumentInterface`\<`Record`\<`string`, `any`>>\[]

##### runId

`string`

##### parentRunId?

`string`

##### tags?

`string`\[]

#### Returns

`void`

#### Overrides

`BaseCallbackHandler.handleRetrieverEnd`

***

### handleRetrieverStart()

> **handleRetrieverStart**(`_retriever`, `query`, `runId`, `parentRunId?`, `tags?`, `metadata?`, `name?`): `void`

Defined in: [src/lib/logger/langchain/tracer.ts:488](https://github.com/maximhq/maxim-js/blob/main/src/lib/logger/langchain/tracer.ts#L488)

#### Parameters

##### \_retriever

`Serialized`

##### query

`string`

##### runId

`string`

##### parentRunId?

`string`

##### tags?

`string`\[]

##### metadata?

`Record`\<`string`, `unknown`>

##### name?

`string`

#### Returns

`void`

#### Overrides

`BaseCallbackHandler.handleRetrieverStart`

***

### handleToolEnd()

> **handleToolEnd**(`output`, `runId`, `parentRunId?`, `tags?`): `void`

Defined in: [src/lib/logger/langchain/tracer.ts:609](https://github.com/maximhq/maxim-js/blob/main/src/lib/logger/langchain/tracer.ts#L609)

Called at the end of a Tool run, with the tool output and the run ID.

#### Parameters

##### output

`any`

##### runId

`string`

##### parentRunId?

`string`

##### tags?

`string`\[]

#### Returns

`void`

#### Overrides

`BaseCallbackHandler.handleToolEnd`

***

### handleToolError()

> **handleToolError**(`error`, `runId`, `parentRunId?`, `tags?`): `void`

Defined in: [src/lib/logger/langchain/tracer.ts:665](https://github.com/maximhq/maxim-js/blob/main/src/lib/logger/langchain/tracer.ts#L665)

Called if a Tool run encounters an error

#### Parameters

##### error

`any`

##### runId

`string`

##### parentRunId?

`string`

##### tags?

`string`\[]

#### Returns

`void`

#### Overrides

`BaseCallbackHandler.handleToolError`

***

### handleToolStart()

> **handleToolStart**(`tool`, `input`, `runId`, `parentRunId?`, `tags?`, `metadata?`, `runName?`): `void`

Defined in: [src/lib/logger/langchain/tracer.ts:562](https://github.com/maximhq/maxim-js/blob/main/src/lib/logger/langchain/tracer.ts#L562)

Called at the start of a Tool run, with the tool name and input
and the run ID.

#### Parameters

##### tool

`Serialized`

##### input

`string`

##### runId

`string`

##### parentRunId?

`string`

##### tags?

`string`\[]

##### metadata?

`Record`\<`string`, `unknown`>

##### runName?

`string`

#### Returns

`void`

#### Overrides

`BaseCallbackHandler.handleToolStart`