@scopeblind/langchain

Veritas Acta evidence wrapper for LangChain tool calls. Every tool invocation automatically produces a cryptographically signed evidence chain: decision → execution → outcome.

Install

npm install @scopeblind/langchain

Usage

Wrap a Single Tool

import { wrapTool } from '@scopeblind/langchain';

const config = {
  issuer: 'my-gateway',
  privateKey: '...', // Ed25519 hex seed (optional — unsigned if omitted)
  onReceipt: (receipt) => console.log('📋', receipt.receipt_type, receipt.receipt_id),
};

// Wrap any LangChain tool
const protectedTool = wrapTool(myTool, config);

// Use it normally — receipts are generated automatically
const result = await protectedTool.invoke({ query: 'search term' });

Wrap All Tools

import { wrapToolkit } from '@scopeblind/langchain';

const tools = wrapToolkit([searchTool, calculatorTool, fileTool], config);

Push to Evidence Indexer

const config = {
  issuer: 'my-gateway',
  indexerEndpoint: 'https://evidence-indexer.tomjwxf.workers.dev',
  indexerApiKey: 'your-api-key',
};

Callback Handler (for existing chains)

import { createCallbackHandler } from '@scopeblind/langchain';

const handler = createCallbackHandler(config);
const chain = new AgentExecutor({ tools, callbacks: [handler] });

Policy Enforcement

const config = {
  issuer: 'my-gateway',
  enforce: true,
  policy: (toolName, args) => {
    if (toolName === 'delete_file') return 'deny';
    return 'allow';
  },
};

Receipt Chain

Each tool call produces 3 linked receipts:

⚖️  decision (allow/deny)
  └──[caused_by]──▶ ⚡ execution (input_hash)
                       └──[caused_by]──▶ 📦 outcome (output_hash, duration_ms)

Protocol

Built on Veritas Acta — the open evidence protocol for machine decisions.

npm install @veritasacta/protocol  # MIT-licensed protocol types

License

MIT — ScopeBlind