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

# LangChain

> Use MengramRetriever in LangChain RAG pipelines and chains for persistent memory.

## Installation

```bash theme={null}
pip install langchain-mengram
```

## MengramRetriever

Subclasses `BaseRetriever` from LangChain. Searches across all 3 memory types and returns `Document` objects.

```python theme={null}
from langchain_mengram import MengramRetriever

retriever = MengramRetriever(
    api_key="om-your-key",
    user_id="alice",
    top_k=5,
    memory_types=["semantic", "episodic", "procedural"],
)

# Use as any LangChain retriever
docs = retriever.invoke("deployment issues")
for doc in docs:
    print(doc.page_content)
    print(doc.metadata)  # {"source": "mengram", "memory_type": "semantic", ...}
```

## Use in a chain

```python theme={null}
from langchain_openai import ChatOpenAI
from langchain_core.prompts import ChatPromptTemplate
from langchain_core.output_parsers import StrOutputParser
from langchain_core.runnables import RunnablePassthrough

retriever = MengramRetriever(api_key="om-...")

prompt = ChatPromptTemplate.from_template(
    "Context from memory:\n{context}\n\nQuestion: {question}"
)

chain = (
    {"context": retriever, "question": RunnablePassthrough()}
    | prompt
    | ChatOpenAI(model="gpt-4o")
    | StrOutputParser()
)

answer = chain.invoke("What deployment stack am I using?")
```

## Cognitive Profile

```python theme={null}
from langchain_mengram import get_mengram_profile

# Get a system prompt string
prompt = get_mengram_profile(api_key="om-...", user_id="alice")
```

## Parameters

| Parameter      | Type | Default                                    | Description           |
| -------------- | ---- | ------------------------------------------ | --------------------- |
| `api_key`      | str  | required                                   | Mengram API key       |
| `user_id`      | str  | "default"                                  | User to search        |
| `api_url`      | str  | "[https://mengram.io](https://mengram.io)" | API base URL          |
| `top_k`        | int  | 5                                          | Max results per type  |
| `memory_types` | list | all 3                                      | Which types to search |