Install an adapter, emit a receipt, verify it offline.

Step 01 · Install

Pick the adapter that matches your AI stack.

If you use LangChain or LangGraph, install langchain-ledgerproof. If you use the OpenAI, Anthropic, Mistral, Cohere, or Google AI SDK directly, install the matching <provider>-ledgerproof. Twenty-nine adapter packages are live on PyPI; see the full adapter catalog.

pip install langchain-ledgerproof

Verify install: pip show langchain-ledgerproof should report 1.0.1 or higher.

Step 02 · Emit

Three lines of Python. Side-channel receipt emission.

The adapter exposes a LangChain CallbackHandler. Attach it once, and every LLM call in your application emits a signed Article 50 transparency receipt to the sink of your choice (log file, queue, webhook, SIEM connector). Your response payloads are untouched. Your latency is unchanged.

from langchain_ledgerproof import LedgerProofCallbackHandler, Ed25519Signer, LogEmitter

signer  = Ed25519Signer()                                # auto-generates an Ed25519 keypair
emitter = LogEmitter(path="./receipts.log")              # any file path; receipts append JSON-Lines

handler = LedgerProofCallbackHandler(
    deployer_id="LEI:529900HNOAA1KXQJUQ27",              # your Legal Entity Identifier
    emitter=emitter,
    signer=signer,
)

# Wire it to any LangChain LLM
from langchain_openai import ChatOpenAI
llm = ChatOpenAI(model="gpt-4o", callbacks=[handler])
response = llm.invoke("Hello, world.")

After invoke() returns, ./receipts.log contains one signed receipt with the prompt hash, response hash, model identifier, deployer context, and an Ed25519 signature over the canonical CBOR encoding.

Step 03 · Verify

Open the receipt in the reference verifier. No LedgerProof account.

Every receipt is verifiable by anyone with an internet connection — your security team, your regulator, a court-appointed expert, a customer asking for proof. The reference verifier runs entirely in the browser; no upload, no telemetry, no LedgerProof server in the path.

• Open verify.ledgerproofhq.io in any browser.
• Drag-and-drop a single receipt line from ./receipts.log.
• The verifier confirms: the signature is valid (Ed25519), the receipt's Merkle root is in the deployer's published bundle, and — once the next anchor cadence elapses (default 60 minutes) — the bundle root is committed in a Bitcoin OP_RETURN transaction.

All verification logic is open source under Apache 2.0; the verifier is a static Vite + TypeScript SPA. If LedgerProof Inc. disappears tomorrow, every receipt you ever emitted remains independently verifiable.