xat-langchain

XAT signing for LangChain. Every tool call gets an Agent-Signature header.

Based on the x-agent-trust extension in the OpenAPI Extensions Registry.

Install

pip install xat-langchain

Usage

Wrap existing tools

from xat_langchain import XATToolkit

toolkit = XATToolkit(key_file="agent.pem", agent_id="my-agent")
signed_tools = toolkit.wrap(existing_tools)

# Every HTTP call these tools make now carries Agent-Signature
agent = create_react_agent(llm, signed_tools)

Decorator

from xat_langchain import xat_tool
import requests

@xat_tool(key_file="agent.pem", agent_id="my-agent")
def search(query: str) -> str:
    return requests.get(f"https://api.example.com/search?q={query}").text

With AWS KMS (production)

import boto3

kms = boto3.client("kms", region_name="eu-west-2")

async def kms_sign(data: bytes) -> bytes:
    import hashlib
    digest = hashlib.sha256(data).digest()
    response = kms.sign(
        KeyId="arn:aws:kms:eu-west-2:123456:key/abcd",
        Message=digest,
        MessageType="DIGEST",
        SigningAlgorithm="ECDSA_SHA_256"
    )
    return response["Signature"]

toolkit = XATToolkit(kms_sign=kms_sign, agent_id="prod-agent")

Audit trail

from xat_langchain import XATCallbackHandler

handler = XATCallbackHandler()
agent.invoke({"input": "..."}, config={"callbacks": [handler]})
print(handler.signed_calls)

What it does

• Wraps LangChain tool HTTP calls with automatic Agent-Signature signing
• ECDSA P-256 (ES256) over a canonical request string
• Private key never enters memory when using KMS providers
• Works with any LangChain tool that makes HTTP requests

Links

• OpenAPI Extensions Registry
• Integration guide
• XAT Node.js library
• Spectral linter

Author

Raza Sharif, CyberSecAI Ltd

License

Apache-2.0