langchain-onebrain

LangChain integration for OneBrain — a persistent AI memory layer for humans and agents. This package provides chat message history, a retriever, and agent tools that connect LangChain to OneBrain via the official Python SDK.

Architecture: This package wraps onebrain-sdk (not raw HTTP). If OneBrain's API changes, only the SDK needs updating — this package stays stable.

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Installation

pip install langchain-onebrain

Requires Python 3.9+.

Dependencies:

• langchain-core>=0.3,<1
• onebrain-sdk>=1.0,<2

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Configuration

Set your OneBrain API key as an environment variable or pass it directly:

export ONEBRAIN_API_KEY="ob_your_prefix:your_secret_here"

All components accept api_key and base_url parameters to override the defaults.

Environment Variable	Description	Default
ONEBRAIN_API_KEY	Your OneBrain API key	— (required)
ONEBRAIN_BASE_URL	Base URL for self-hosted instances	https://onebrain.rocks/api/eu

Getting an API Key

1. Sign in at onebrain.rocks/dashboard.
2. Navigate to Settings > API Keys.
3. Click Create API Key and copy the full key (ob_prefix:secret).

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Quick Start

Chat Message History

Store and retrieve conversation messages as OneBrain memories:

from langchain_onebrain import OneBrainChatMessageHistory
from langchain_core.messages import HumanMessage, AIMessage

# Create a history backed by OneBrain
history = OneBrainChatMessageHistory(
    api_key="ob_xxx:secret",
    session_id="session-abc-123",
)

# Add messages
history.add_user_message("What is the weather like?")
history.add_ai_message("I don't have real-time weather data.")

# Retrieve all messages
for msg in history.messages:
    print(f"{msg.type}: {msg.content}")

# Clear (archives messages, does not delete)
history.clear()

With ConversationChain

from langchain.chains import ConversationChain
from langchain_openai import ChatOpenAI
from langchain_onebrain import OneBrainChatMessageHistory

llm = ChatOpenAI(model="gpt-4")
memory_history = OneBrainChatMessageHistory(session_id="user-42")

chain = ConversationChain(
    llm=llm,
    memory=ConversationBufferMemory(
        chat_memory=memory_history,
        return_messages=True,
    ),
)

response = chain.predict(input="Tell me about quantum computing.")

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Retriever

Search OneBrain memories and return them as LangChain documents:

from langchain_onebrain import OneBrainRetriever

retriever = OneBrainRetriever(
    api_key="ob_xxx:secret",
    top_k=5,
    search_mode="hybrid",  # "keyword", "vector", or "hybrid"
)

# Use directly
docs = retriever.invoke("user preferences for dark mode")
for doc in docs:
    print(doc.page_content)
    print(doc.metadata)  # id, type, confidence, score, source_type, created_at

With RetrievalQA

from langchain.chains import RetrievalQA
from langchain_openai import ChatOpenAI
from langchain_onebrain import OneBrainRetriever

llm = ChatOpenAI(model="gpt-4")
retriever = OneBrainRetriever(top_k=10, search_mode="hybrid")

qa = RetrievalQA.from_chain_type(
    llm=llm,
    retriever=retriever,
    chain_type="stuff",
)

answer = qa.invoke("What are the user's coding preferences?")
print(answer["result"])

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Agent Tools

Four tools for use with LangChain agents:

from langchain_onebrain import (
    OneBrainSearchTool,
    OneBrainWriteTool,
    OneBrainContextTool,
    OneBrainEntityTool,
)

# Create tools
search = OneBrainSearchTool(api_key="ob_xxx:secret")
write = OneBrainWriteTool(api_key="ob_xxx:secret")
context = OneBrainContextTool(api_key="ob_xxx:secret")
entity = OneBrainEntityTool(api_key="ob_xxx:secret")

# Use with an agent
from langchain_openai import ChatOpenAI
from langchain.agents import AgentExecutor, create_openai_tools_agent
from langchain_core.prompts import ChatPromptTemplate, MessagesPlaceholder

llm = ChatOpenAI(model="gpt-4")
tools = [search, write, context, entity]

prompt = ChatPromptTemplate.from_messages([
    ("system", "You are a helpful assistant with access to the user's memory."),
    MessagesPlaceholder("chat_history", optional=True),
    ("human", "{input}"),
    MessagesPlaceholder("agent_scratchpad"),
])

agent = create_openai_tools_agent(llm, tools, prompt)
executor = AgentExecutor(agent=agent, tools=tools)

result = executor.invoke({"input": "What do you know about my work projects?"})
print(result["output"])

Tool Reference

Tool	Name	Description
OneBrainSearchTool	onebrain_search	Search memories with keyword/vector/hybrid modes
OneBrainWriteTool	onebrain_write	Store new memories (facts, preferences, goals, etc.)
OneBrainContextTool	onebrain_context	Get optimized user context (brief/assistant/project/deep)
OneBrainEntityTool	onebrain_entity	List entities (people, organizations, tools)

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Self-Hosted Setup

OneBrain supports self-hosted deployments. Point the SDK to your instance:

from langchain_onebrain import OneBrainRetriever

retriever = OneBrainRetriever(
    api_key="ob_xxx:secret",
    base_url="https://brain.your-company.com/api/v1",
)

Or set the environment variable:

export ONEBRAIN_BASE_URL="https://brain.your-company.com/api/v1"

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API Reference

OneBrainChatMessageHistory

Parameter	Type	Default	Description
api_key	str | None	None	OneBrain API key (or ONEBRAIN_API_KEY env var)
session_id	str	"default"	Unique session identifier
base_url	str | None	None	API base URL override

Methods:

• messages — Property returning List[BaseMessage]
• add_message(message) — Store a single message
• add_messages(messages) — Store multiple messages
• clear() — Archive all session messages

OneBrainRetriever

Parameter	Type	Default	Description
api_key	str | None	None	OneBrain API key
top_k	int	10	Maximum results
search_mode	str	"hybrid"	Search mode: keyword/vector/hybrid
base_url	str | None	None	API base URL override
alpha	float | None	None	Keyword/vector balance (0.0-1.0)

Methods:

• invoke(query) / _get_relevant_documents(query) — Returns List[Document]

OneBrainSearchTool

Parameter	Type	Default	Description
query	str	—	Search query (required)
top_k	int	10	Maximum results
mode	str	"hybrid"	Search mode

OneBrainWriteTool

Parameter	Type	Default	Description
title	str	—	Memory title (required)
body	str	—	Memory content (required)
memory_type	str	"fact"	Type: fact/preference/decision/goal/experience/skill

OneBrainContextTool

Parameter	Type	Default	Description
scope	str	"deep"	Scope: brief/assistant/project/deep

OneBrainEntityTool

Parameter	Type	Default	Description
entity_type	str | None	None	Filter by entity type
limit	int	20	Maximum results

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Development

git clone https://github.com/azappnew/langchain-onebrain.git
cd langchain-onebrain
python -m venv .venv
source .venv/bin/activate
pip install -e ".[dev]"

# Run tests
pytest tests/ -v

# With coverage
pytest tests/ -v --cov=langchain_onebrain --cov-report=term-missing

# Lint
ruff check src/ tests/

# Type check
mypy src/

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License

MIT License. See LICENSE for details.

Copyright (c) 2026 AZapp One.