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

# AgentSystems Notary

> Cryptographically verifiable audit trails for LangChain applications.

## Overview

AgentSystems Notary creates tamper-evident audit trails for AI agent interactions.

## Why

When AI behavior is questioned by customers, auditors, regulators, insurers, etc., you need to prove what actually happened. Traditional logs don't work: you control them, so third parties have to trust you didn't modify them.

Tamper-evident logging removes that trust requirement.

## How it works

Raw LLM interactions stay in your storage. No third party sees them during normal operation. But cryptographic hashes of each interaction are written to independent, tamper-evident storage (Arweave or the AgentSystems custodied service) at the same time.

If there's ever an audit or dispute, you provide the raw logs. The auditor re-hashes them and compares against the stored hashes. A match indicates the logs are unaltered. A mismatch indicates tampering or corruption.

You control your data, but can't alter it without detection.

**What gets logged:**

* To your storage: full raw LLM payload (prompts, responses, metadata, timestamps)
* To hash storage: SHA-256 hash + metadata (e.g. namespace, session ID, timestamps)

## Hash storage options

Hashes (not raw data) can be written to either storage option:

| Storage                                                                                                                              | Best For           | Features                                                               |
| ------------------------------------------------------------------------------------------------------------------------------------ | ------------------ | ---------------------------------------------------------------------- |
| [Decentralized (Arweave)](https://docs.agentsystems.ai/notary/configuration/hash-storage?utm_source=langchain-docs\&utm_medium=docs) | No vendor lock-in  | Public append-only ledger, open-source verification, no account needed |
| [`Custodied`](https://agentsystems.ai/notary?utm_source=langchain-docs\&utm_medium=docs)                                             | Managed compliance | Write-once storage, verification UI, signed attestations for audits    |

<Info>
  [Custodied plans](https://agentsystems.ai/notary?utm_source=langchain-docs\&utm_medium=docs) offer WORM-compliant hash storage, managed signing, and signed attestations.
</Info>

## Prerequisites

```shell theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
pip install agentsystems-notary langchain langchain-anthropic python-dotenv
```

## Example (decentralized)

<Steps>
  <Step title="Generate signing key">
    ```shell theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
    openssl genrsa -out arweave-key.pem 4096
    ```

    <Warning>
      Retain this key. It is required to prove ownership of on-chain hashes during verification.
    </Warning>

    For production, use a [cloud key management service](https://docs.agentsystems.ai/notary/configuration/signing?utm_source=langchain-docs\&utm_medium=docs).
  </Step>

  <Step title="Create .env file">
    Create a `.env` file in your project root:

    ```
    # AWS S3 for raw payload storage
    ORG_AWS_S3_BUCKET_NAME=your-bucket
    ORG_AWS_S3_ACCESS_KEY_ID=AKIA...
    ORG_AWS_S3_SECRET_ACCESS_KEY=...
    ORG_AWS_S3_REGION=us-east-1

    # Path to signing key
    ARWEAVE_PRIVATE_KEY_PATH=./arweave-key.pem

    # Anthropic
    ANTHROPIC_API_KEY=sk-ant-...
    ```
  </Step>

  <Step title="Run the example">
    ```python theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
    import os

    from agentsystems_notary import (
        LangChainNotary,
        ArweaveHashStorage,
        AwsS3StorageConfig,
        LocalKeySignerConfig,
        RawPayloadStorage,
    )
    from langchain_anthropic import ChatAnthropic
    from dotenv import load_dotenv

    load_dotenv()

    # Your S3 bucket for raw LLM payloads
    s3_config = AwsS3StorageConfig(
        bucket_name=os.environ["ORG_AWS_S3_BUCKET_NAME"],
        aws_access_key_id=os.environ["ORG_AWS_S3_ACCESS_KEY_ID"],
        aws_secret_access_key=os.environ["ORG_AWS_S3_SECRET_ACCESS_KEY"],
        aws_region=os.environ["ORG_AWS_S3_REGION"],
    )
    raw_payload_storage = RawPayloadStorage(storage=s3_config)

    # Local RSA key for signing
    signer = LocalKeySignerConfig(
        private_key_path=os.environ["ARWEAVE_PRIVATE_KEY_PATH"],
    )

    # Arweave for decentralized hash storage
    # Namespace is public — written to the ledger and used to segment stored data
    # Namespace should be one anonymous ID per customer, agent, or environment
    # Retain a record of your namespace mappings
    arweave_storage = ArweaveHashStorage(
        namespace="tenant_a1b2c3d4",  # See namespace comments above
        signer=signer,
    )

    # Create notary callback
    notary = LangChainNotary(
        raw_payload_storage=raw_payload_storage,
        hash_storage=[arweave_storage],
        debug=True,
    )

    # Attach to model
    model = ChatAnthropic(
        model="claude-sonnet-4-6",
        api_key=os.environ["ANTHROPIC_API_KEY"],
        callbacks=[notary],
    )

    response = model.invoke("What is the capital of France?")
    print(response.content)
    ```
  </Step>
</Steps>

## Verification

**Decentralized (Arweave)**: Download raw payloads from your storage bucket, zip them, and verify with the open-source CLI:

```shell theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
aws s3 sync s3://your-bucket/arweave/tenant_a1b2c3d4/ ./logs
zip -r logs.zip logs
npm install -g agentsystems-verify
agentsystems-verify --logs logs.zip
```

The CLI re-hashes each payload and compares against the hashes stored on Arweave. See the [full verification guide](https://docs.agentsystems.ai/notary/verification/arweave?utm_source=langchain-docs\&utm_medium=docs) for details.

Alternatively, the [Verify UI](https://verify.agentsystems.ai?utm_source=langchain-docs\&utm_medium=docs) supports both decentralized and custodied verification.

## Configuration

* [Raw payload storage options](https://docs.agentsystems.ai/notary/configuration/raw-payload-storage?utm_source=langchain-docs\&utm_medium=docs)
* [Signing configuration](https://docs.agentsystems.ai/notary/configuration/signing?utm_source=langchain-docs\&utm_medium=docs)
* [Hash storage options](https://docs.agentsystems.ai/notary/configuration/hash-storage?utm_source=langchain-docs\&utm_medium=docs)

## Resources

* [Website](https://agentsystems.ai/notary?utm_source=langchain-docs\&utm_medium=docs)
* [Documentation](https://docs.agentsystems.ai/notary/?utm_source=langchain-docs\&utm_medium=docs)
* [GitHub](https://github.com/agentsystems/agentsystems-notary?utm_source=langchain-docs\&utm_medium=docs)

***

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